Category: 1st PUC

Students can Download 1st PUC Physics Model Question Paper 4 with Answers, Karnataka 1st PUC Physics Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

Karnataka 1st PUC Physics Model Question Paper 4 with Answers

Time: 3.15 Hours
Max Marks: 70

General Instructions:

1. All parts are compulsory.
2. Draw relevant figure / diagram wherever necessary.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer the following questions: ( 10 × 1 = 10)

Question 1.
Name the experiment which established the nuclear model of atom.
Answer:
Geiger-Marsdon experiment on alpha-particle scattering by gold foil.

Question 2.
What is S.I. unit of luminous intensity?
Answer:
The SI unit luminous intensity is candela (cd).

Question 3.
Give an example for two dimensional motion.
Answer:
Projectile motion and circular motion.

Question 4.
Why don’t action and reaction forces cancel each other?
Answer:
Action and reaction forces act on two interacting bodies, so the forces don’t cancel each other.

Question 5.
A light body and a heavy body have the same momentum. Which one will have greater kinetic energy?
Answer:
Since K.E. ∝ \(\frac{1}{m}\) for same linear momentum, lighter body has more kinetic energy.

Question 6.
Give the expression for moment of inertia of a circular disc of radius R about its diameter.
Answer:
I = \(\frac{M R^{2}}{4}\)

Question 7.
What are geostationary satellites?
Answer:
Geo-stationary satellites orbit around the Earth with the speed of the satellite equal to the rotational speed of the Earth. Hence, these satellites appear to be fixed with respect to a place on the surface of the Earth.

Question 8.
What is shear deformation?
Answer:
Shear deformation is the ratio of lateral displacement of one edge to the vertical distance between the opposite faces of the body.

Question 9.
How does melting point of ice changes with increase of pressure?
Answer:
The ice will go to a lower melting point.

Question 10.
Give an example for a wave which can travel through vacuum.
Answer:
Electromagnetic wave.

Part – B

II. Answer any FIVE of the following questions: ( 5 × 2 = 10 )

Question 11.
Given the relative error in the measurement of the radius of a circle is 0.02, whal is the percentage error in the measurement of its area?
Answer:
A = πr²
\(\frac{\Delta \mathrm{A}}{\mathrm{A}}=2 \mathrm{r} \frac{\Delta r}{r}\)
= 2 × r × 0.02 = 0.04r
(\(\frac{\Delta \mathrm{A}}{\mathrm{A}}\)) = 0.04r

Question 12.
What are the significance of velocity – time graph?
Answer:
The slope of the line on a v-t graph gives the acceleration of the particle.

Question 13.
What is resolution of a vector? What is the x-component of a vector A, that makes an angle 300 with x-axis.
Answer:
A single vector can be resolved in two or more number of directions each of which is known as the component of a vector. This splitting is known as resolution of vector.
\(\overrightarrow{\mathrm{A}}_{x}=\left(A \cos 30^{\circ} \hat{i}\right)=\frac{\sqrt{3}}{2} \hat{i}\)

Question 14.
Give the general conditions of equilibrium of a rigid body.
Answer:
(1) The vector sum of the forces on the rigid body is zero for translatory equilibrium
\(\sum_{i=1}^{n} \vec{F}_{i}=0\) and (acceleration a = 0 )
(2) The vector sum of the torques on the rigid body is zero for rotatory equilibrium (a=0) i.e.

i.e., the components of X, Y, and Z independently vanish to zero for linear equilibrium.

Sum of X components, Y components and Z components of torque on the particles, vanish for rotational equilibrium.

Question 15.
Write Stoke’s formula for viscous drag force. Explain the terms.
Answer:
F = 6πηav where v – terminal speed of liquid, η – coefficient of viscosity, a – radius of the spherical object and F – viscous drag force.

Question 16.
What is meant by anomalous behavior of water. What is its significance?
Answer:
The density of water increases from 0°C to 4°C and thereafter decreases with increase of temperature.

This behaviour of water from 0°C to 4°C is known as anomalous expansion of water. Water at 4°C has the maximum density and sinks down. However, water below the surface, relatively having lower density, rises above. Water becomes lighter as the temperature falls below 4°C. Ice at 0°C has the minimum density and floats on water. Hence marine animals can survive below ice. It is water everywhere below ice.

Question 17.
State and explain first law of thermodynamics.
Answer:
The energy (∆Q) supplied to the system goes in partly to increase the internal energy of the system (∆U) and the rest in doing work on the environment (∆W).
∆Q = ∆U + ∆W
where ∆Q → heat supplied, ∆U → change in internal energy, ∆W → work done

Question 18.
What is periodic motion. Give an example.
Answer:
A particle event that repeats itself in regular intervals of time is known as the periodic motion. Both circular and elliptical motions of electrons around the atomic nucleus are examples of periodic motions.

Part – C

III. Answer any FIVE of the following questions : ( 5 × 3 = 15 )

Question 19.
Derive the expression for time of flight of a projectile.
Answer:
Expression for time of flight:

Consider v = (v₀ sinθ) – gt
Put v = 0, fort = time of ascent = t_a
t_a = \(\frac{v_{0} \sin \theta}{g}\)
but time of ascent = time of descent
and time of flight T = t_a + t_d
i.e., T = \(\frac{2 v_{0} \sin \theta}{g}\) and T ∝ v₀ for a given angle of projection.

Question 20.
Arrive at the statement of principle of conservation of linear momentum from Newton’s laws of motion.
Answer:
Statement: In an isolated system of collision of bodies, the total linear momentum before impact is equal to the total linear momentum after impact.

Let m₁ and m₂ be the masses of two bodies moving along \(\vec{v}_{1 i}\) and \(\vec{v}_{2 i}\). Let \(\vec{v}_{1 f}\) and be the \(\vec{v}_{2 f}\) be final velocities after the impact.
At the time of impact the force of action acts on the body B and the force of reaction acts on A.
Applying Newton’s III law of motion
\( |Force of action on \mathrm{B}|=-| Force of reaction on \mathrm{A} |\)

This shows that the total final linear momentum of the isolated system equals its total initial momentum.

Question 21.
Prove that potential energy stored in a spring is, where k is the force constant of the spring and x is the change in length Of the spring.
Answer:
Work done by the spring force = Ws= \(-\int_{0}^{x_{\mathrm{m}}} \mathrm{F}_{\mathrm{s}} \mathrm{d} \mathrm{x}\)
W = \(=-\int_{0}^{x_{m}} \mathrm{k} x \mathrm{d} \mathrm{x}\)
W = \(-\frac{1}{2} \mathrm{k} x_{\mathrm{m}}^{2}\)
Work done by the external pulling force = W= \(\frac{1}{2} \mathrm{k} x_{\mathrm{m}}^{2}\)

Question 22.
State Kepler’s laws of planetary motion.
Answer:
Kepler’s I law (Law of orbit): All planets revolve in elliptical orbits with Sun as one of its foci.

2a – Major axis length
2b – Minor axis length
S-Sun at one focus P
S¹ – The other focus of the ellipse
P – Perihelion position of the planet.
A – Apehelion position of the planet.

Kepler’s II law (Law of areas) : The line joining the planet and the Sun sweeps out equal areas in equal intervals of time.
\(\frac{\Delta \overrightarrow{\mathrm{A}}}{\Delta \mathrm{t}}=\frac{1}{2 \mathrm{m}} \overrightarrow{\mathrm{L}}\)

Kepler’s III law (Law of periods) : The square of the period of revolution of a planet around the sun is directly proportional to the cube of the semi major axis of the ellipse.
i.e., T² ∝ a³ so that for two planets
\(\left(\frac{T_{1}}{T_{2}}\right)^{2}=\left(\frac{a_{1}}{a_{2}}\right)^{3}\)

Question 23.
Prove that the centre of mass of a system moves with constant velocity in the absence of external force on the system.
Answer:
When there is no external force the acceleration of the body is zero.
Force = rate of change of momentum.

∴M is not zero
so this proves that velocity will always be constant in such scenario.

Question 24.
State and explain Hooke’s law. Define modulus of elasticity.
Answer:
Statement: The ratio of stress to strain is a constant for a material within the elastic limit.
Modulus of elasticity = \(\frac{\text { Stress }}{\text { Strain }}\)

Within the elastic limit, stress v/s strain is a straight line ‘A’ is the elastic limit upto which Hooke’s law is applicable. Beyond ‘B’ the yielding point, the wire extends but does not return to the initial state when the deforming force is removed. ‘F’ is the breaking point. ‘EF’ allows the material to be malleable and ‘DE’, ductile.

Question 25.
State Bernoulli’s theorem. What are its applications?
Answer:
Along a steamline, in a steady flow of non viscous fluid, potential energy, kinetic energy and pressure energy remain constant.
Applications

• Uplift of air craft and
• Atomisers work on the principle of Bernoulli’s theorem.

Question 26.
What is Doppler effect. Write any two applications of Doppler’s effect.
Answer:
The phenomenon of apparent change in frequency due to relative motion between the source of sound and the listener (observer) is known as Doppler effect.
Applications of Doppler effect:

1. It is used in radar.
2. It is used by meteorologists to track storms.
3. Doppler effect of sound is used to diagnose heart problems in the hospital.

Part – D

IV. Answer any TWO of the following questions : ( 2 × 5 = 10 )

Question 27.
Find the magnitude and direction of the resultant of two vectors A and B in terms of their magnitudes and angle, between them.
Answer:
To find the magnitude of the resultant:
From the OAC, \(\vec{P}+\vec{Q}=\vec{R}\)
CD is ⊥^r to OD. From the pythagoras theorem,
OC² = OD² + DC² ……….(1)
but DC² = AC² + AD² ……..(2)
From the right angled triangle ADC,
sinθ = CD/AC
∴AC sinθ = CD …….(3)
cosθ = AD /AC
ie., AD = AC cosθ ……..(4)
Eqn. (1) can be written as
OC² = (OA + AD)² + DC²
sin OC² = OA² + AD² + 20A.AD + DC²
using (2) and (4) we get
OC² = OA² + AC² + 20A. AC cosθ
i.e. R² + P² + Q² + 2PQ cosθ
Hence, R = (P² + Q² + 2PQ cosθ)^1/2
To find the direction of the resultant:

Question 28.
State Newton’s second law of motion and hence derive F= ma.
Answer:
Newton’s II law of motion:
Statement: “The rate of change in the linear momentum of a body is directly proportional to the impressed force and takes place in the direction of force applied.
To show that \(\vec{F}=m \vec{a}\).
Let m be the mass of the body. Let be the initial linear momentum. Let be the final linear momentum as a result of the impressed force.
By definition \(\lim _{\Delta t \rightarrow 0} \frac{\Delta \vec{p}}{\Delta t}=\frac{d \vec{p}}{d t}\) where \(\Delta \vec{p}=\vec{p}_{f}-\vec{p}_{i}\), and \(\frac{d \vec{p}}{d t}\) is instantaneous acceleration.
From Newton’s II law of motion,

But the magnitude of force \(|\overrightarrow{\mathrm{F}}|\) is so defined that k = 1 : We denote \(|\vec{F}|=m|\vec{a}|\)
Thus F=ma and \(\vec{F}=m \vec{a}\).

Question 29.
Define torque. Show that torque on a particle is equal to rate of change of its angular momentum.
Answer:
The rotating effect of force is called torque and is represented by \(\vec{\tau}=\overrightarrow{\mathrm{r}} \times \overrightarrow{\mathrm{F}}\).
i.e. t=rFsin8
where O is the angle between r and F.
Fora system of n particles,
Net angular momentum = \(\overrightarrow{\mathrm{L}}=\overrightarrow{\mathrm{L}_{1}}+\overrightarrow{\mathrm{L}_{2}}+\ldots \ldots . \overrightarrow{\mathrm{L}_{n}}=\sum \overrightarrow{\mathrm{r}_{1}} \times \overrightarrow{\mathrm{p}_{1}}\)

V. Answer any TWO of the following questions : ( 2 × 5 = 10 )

Question 30.
Using kinetic theory of gases derive an expression for finding the pressure of an ideal gas in terms of mean squared speeds of the molecules.
Answer:
Let an ideal gas be enclosed in a cubical vessel of side l. Area of cross wall will be A =l². Let V_x be the velocity of the molecule hitting the plane of wall (of the vessel) YZ. After collision, it rebounds with the same speed but in the opposite direction along a straight line. The change in ‘ velocity of the molecule along the X direction is v_x – (-v_x) = 2v_x.
The change in linear momentum imparted to the wall in the collision process = 2.mvx where m is the mass of the molecule.
But force exerted on the wall = rate of change in momentum = \(\frac{2 m v_{x}}{\Delta t}\)
Pressure exerted on the wall due to 1 molecule = \(\frac{\text { Force }}{\text { Area }}\)
∴Pressure due to single molecule = \(\frac{2 m v_{x}}{\left(A^{2}\right) \Delta t}\) where A = l².
Total number of molecules hitting the wall and returning back = (Volume) (number density) Distance travelled by the molecule = (v_x∆t)
Volume covered = (v_x∆t)(A)
Total number of molecules hitting the wall on an average = \(\frac{1}{2}\) (vx∆tA)(n)
Hence pressure exerted on the wall = P
P = \(\left(\frac{2 m v_{x}}{A \Delta t}\right)\left(\frac{1}{2} v_{x} \Delta t A n\right)\)
i.e., P = mnv_x²

By symmetry (isotropic condition of speed)
\(\overline{\mathbf{v}}_{x}^{2}=\overline{\mathbf{v}}_{y}^{2}=\overline{\mathbf{v}}_{z}^{2}\)
So, the mean of the squred speed along any one axis
= (\(\frac{1}{3}\)) \(\overline{\mathbf{v}^{2}}\)
Thus P = mn (\(\frac{1}{3}\)\(\overline{\mathbf{v}^{2}}\)).
i.e., P = \(\frac{1}{3}\)mn\(\overline{\mathbf{v}^{2}}\)

Question 31.
Describe Carnot’s cycle and write the expression for its efficiency.
Answer:
Working of Carnot’s engine:
Step 1 : The working substance (ideal gas) is enclosed ¡n a non-conducting wall and conducting bottom of a cylinder fitted with air tight non conducting piston. This is placed on the source having an infinite thermal capacity at a steady temperature.
The top surface is conducting and the rest non conducting. As a result, the gas expands isothermally. The work done
by the system.
Q = W₁ = μRT₁ log\(\frac{V_{2}}{V_{1}}\)(curve A B)

Step 2 : The working substance is now placed on a non L conducting platform. as a result ofwhich no heat exchange takes place between the system and the surroundings. [he system expands adiabatically at the expense of its internal energy. The gas cools. The work done by the system.
\(\mathrm{W}_{2}=\frac{\mu \mathrm{R}}{\gamma-1}\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)\)(curve B C)

Step 3 : The working substance is now placed on the sink maintained at a steady low temperature T,K. The system undergoes isothermal compression at this temperature. The pressure of gas increases and volume decreases without any change in the internal energy and specific heat of gas remains at infinity.
\(\mathrm{W}_{3}=\mu \mathrm{RT}_{2} \log \left(\frac{\mathrm{V}_{4}}{\mathrm{V}_{3}}\right)\) (curve C D)

Step 4: The working substance is placed on a non-conducting platform, Under thermal isolation. the system undergoes change in its internal energy and its specific heat remains at zero. Adiabatic compression results in increase in the pressure and temperature at the expense of work being done on the system. The system is allowed to reach its initial slate. This completes one cycle of operation. The area hounded by the curves gives the amount of heat converted into work.
\(\mathrm{W}_{4}=\frac{-\mu \mathrm{R}}{\gamma-1}\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)\) (curve D A)
i.e., Net work done = W =W₁ + W₂ +W₃ + W₄
Work done = μR(T – T₂) \(\log _{e}\left(\frac{V_{2}}{V_{1}}\right)\)
∴Efficiency η = \(\frac{\mathrm{w}}{\mathrm{Q}}=1-\frac{\mathrm{T}_{2}}{\mathrm{T}_{1}}\)

Question 32.
Derive the Newton’s formula to find the speed of a longitudinal wave in an ideal gas. What is the Laplace correction to obtain the speed of sound in air?
Answer:
v = \(\sqrt{\frac{p}{\rho}}\) where ‘p’is pressure on gaseous medium. ρ – density of gaseous medium.
Consider adiabatic variation in the pressure and volume of gaseous medium.
PV = constant.
Since no change of heat takes place between the system and the surrounding.
A(PV^γ) = 0
i.e., γPV^γ-1   ∆V+V^γ    ∆P = 0
i.e., Bulk modulus = \(-\frac{\Delta \mathrm{P}}{\frac{\Delta \mathrm{V}}{\mathrm{V}}}\) = γP
Hence in the expression V = \(\sqrt{\frac{\mathrm{E}}{\rho}}\), Elasticity ‘E is replaced by γP.
Laplace equation is written as v = \(=\sqrt{\frac{\gamma \mathrm{P}}{\rho}}\).
Where γ = 1 + 2/f and ‘f’ is number of degrees of freedom of gaseous molecule.

VI. Answer any THREE of the following questions : ( 3 × 5 = 15 )

Question 33.
Two towns A and B are connected by a regular bus service with a bus leaving in either direction every T minutes. A man cycling with a speed of 20 km h in the direction A to B notices that a bus goes past him every 18 min in the direction of his motion, and every 6 min in the opposite direction. What is the period T of the bus service and with what speed (assumed constant) do the buses ply on the road?
Answer:
The distance between two buses just when one takes is vT.
u = 20 km/hr
When they move in the same direction, relative velocity = v – u
The time to cover the distance,
t= 18 mm = \(\frac{18}{60}\)hrs
distance = t (v-u)
t (v-u) = vT
vT = \(\frac{3}{10}\)(v-u)……..(1)
When they move in the opposite direction, relative velocity = v + u
∴Time to cover the distance, t = 6 minutes = \(\frac{6}{60}\)hrs
∴t (v + u) = vT
vT = \(\frac{1}{10}\)(v + u)……..(2)
Equating vT from the eqn (1) and (2)
\(\frac{3}{10}\)(v-u) = \(\frac{1}{10}\)(v + u)
3v – 3u = v + u
∴v = 2u
v = 40 km/hr …….(3)
Substituting in eqn (2)
40 xT = \(\frac{1}{10}\)(40 + 20)
T = \(\frac{3}{20}\)hrs
T = 9 minutes.

Question 34.
A person trying to lose weight(dieter) lifts a 10 kg mass, one thousand times, to a height of 0.5 in each time. Assume that the potential energy lost each time she lowers the mass is dissipated, (a) How much work does she do against the gravitational force? (b) Fat supplies 3.8 × 10⁷ J of energy per kilogram which is converted to mechanical energy with a 20% efficiency rate. How much fat will the dieter use up?
Answer:
Given m = 10 kg, g = 9.8 ms^-2 , h = 0.5m, n = 1000
Energy supplied by fat is 3.8 × 10⁷ J /kg, efficiency = 20%
∴20 % of energy supplied by fat = 3.8 × 10⁷ × 0.20 = 0.76 × 10^-7 Jkg^-1
Work done against the gravity = n mgh =10³ × 10 × 9.8 × 0.5 = 4.9 × 10⁴J
Mass of fat used = \(\frac{4.9 \times 10^{4}}{0.76 \times 10^{7}}\) = 6.45 × 10^-3 kg

Question 35.
Phobos is a satellite of the planet mars. Phobos has a period 7 hours, 39 minutes and an orbital radius of 9.4 × 10³ km. calculate the mass of mars. Assume that earth and mars move in circular orbits around the sun, with martian orbit being 1.52 times the orbital radius of earth. What 1 the length of the martian year in days?
Answer:
T = \(\frac{4 \pi^{2}}{\mathrm{GM}_{m}} \mathrm{R}^{3}\) M = \(\frac{4 \pi^{2}}{\mathrm{G}} \frac{\mathrm{R}^{3}}{\mathrm{T}^{2}}\)
M_m = \(=\frac{4 \times(3.14)^{2} \times(9.4)^{3} \times 10^{18}}{6.67 \times 10^{-11} \times(459 \times 60)^{2}}\)
M_m = 6.48 × 10 kg
Using Kepler’s III law,
\(\frac{\mathrm{T}_{\mathrm{M}}^{2}}{\mathrm{T}_{\mathrm{E}}^{2}}=\frac{\mathrm{R}_{\mathrm{MS}}^{3}}{\mathrm{R}_{\mathrm{ES}}^{3}}\)
Where R_MS → Mars sun distance
R_ES → Earth – sun distance
∴T_M = \((1.52)^{\frac{3}{2}}\) × 365
T_M = 684 days.

Question 36.
‘Thermacole’ icebox is a cheap and efficient method for storing small quantities of cooked food in summer in particular. A cubical icebox of side 30 cm has a thickness of 5.0 cm. If 4.0 kg of ice is put in the box, estimate the amount of ice remaining after 6h. The outside temperature is 45° C, and co-efficient of thermal conductivity of thermacole is 0.01 J s^-1m^-1K^-1. [ Heat of fusion of water = 335 × 10 J kg].
Answer:
Given, L = 3.36 × 105 Jkg^-1     K = 0.01 Wm^-1K^-1
d = 0.05 m, t = 6 × 3600 = 21600s
A = 0.3 × 0.3 = 0.09 m², θ₁ ≈ θ₂,= 45°C
We know that Q = \(\frac{\mathrm{KA}\left(\theta_{1}-\theta_{2}\right) \mathrm{t}}{\mathrm{d}}\) = mL

Question 37.
A spring balance has a scale that reads from 0 to 50 kg. The length of the scale is 20 cm. A body suspended from this balance, when displaced and released, oscillates with a period of 0.6 s. What is the weight of the body?
Answer:
Spring constant = \(\frac{50 \mathrm{kg}}{0.2 \mathrm{m}}\) =250 kgm^-1
We know that T = \(=2 \pi \sqrt{\frac{m}{k}}\) ; T = 0.6s (given)
i.e., m = \(\frac{\mathrm{kT}^{2}}{4 \pi^{2}}=\frac{250 \times(0.6)^{2}}{4 \times(3.142)^{2}}\)
m = 2.279 kg.

Students can Download 1st PUC Physics Model Question Paper 3 with Answers, Karnataka 1st PUC Physics Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

Karnataka 1st PUC Physics Model Question Paper 3 with Answers

Time: 3.15 Hours
Max Marks: 70

General Instructions:

1. All parts are compulsory.
2. Draw relevant figure / diagram wherever necessary.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer the following questions: ( 10 × 1 = 10 )

Question 1.
What is physics?
Answer:
Physics deals with the laws of nature and natural phenomena associated with matter and energy.

Question 2.
Give the number of significant figures in 5.300 × 10³.
Answer:
Four

Question 3.
What is the angle between velocity and acceleration at the peak point of a projectile projected for maximum range?
Answer:
– 90° or 270°

Question 4.
What is the use of mechanical advantage of a lever?
Answer:
The mechanical advantage of the lever is the ratio of output force to input force. By using lever with a little effect more work can be derived.

Question 5.
Name the experiment to measure the value of gravitational constant.
Answer:
Cavendish experiment.

Question 6.
Which property of a body is responsible for regaining its shape and size when deforming force acting on it is removed?
Answer:
Elasticity.

Question 7.
Name the instrument used to measure atmospheric pressure.
Answer:
Barometer.

Question 8.
What is absolute zero temperature?
Answer:
Absolute zero of temperature is that temperature of a gas at which its volume and pressure become zero.
Zero kelvin = -273.15°C ≈ -273°C.

Question 9.
Define mean free path.
Answer:
The average distance a molecule can travel without colliding is called the mean free path.

Question 10.
What is the basis of the phenomenon of interference?
Answer:
The two interfering waves should be identical and superpose at a point at small angles (travelling in the same direction) so that modification of energy takes place at the point of superposition of waves.

Part – B

II. Answer any FIVE of the following questions: ( 5 × 2 = 10 )

Question 11.
What is parallax? Mention its use.
Answer:
Parallax is the change in the position of an object with respect to it background, when the object is seen from two different positions.
Parallax is used to determine long distance.

Question 12.
A car is traveling with a uniform velocity of 30ms^-1. The driver applies the breaks and the car comes to rest in 10 seconds. Calculate the retardation.
Answer:
u = 300 ms^-1
t = 10s
v = 0
∴a = \(\frac{v-u}{t}=\frac{0-30}{10} = -3 \mathrm{ms}^{-2}\)
∴ Retardation is 3 ms^-2.

Question 13.
Distinguish between scalars and vectors.
Answer:
Scalars:

• Scalars require only magnitude to represent them.
• Scalars require simple algebraic rules for addition or subtraction.

Vectors:

• Vectors require both magnitude and direction to represent them.
• Vectors require law of polygon of addition of vectors.

Question 14.
When is the work done negative? Give an example.
Answer:
If the force and the displacement are in opposite directions, then the work is said to be negative. Work done by a force against the gravity is negative.

Question 15.
State the law of conservation of angular momentum. Illustrate with an example.
Answer:
If the total external torque on a system is zero then the total angular momentum of the system is conserved (remains constant)

Ballet dancer : Ballet dancers bring their arms closer to their body in order to increase the angular speed and decrease the moment of inertia. In order to decrease the angular speed, they stretch their arms out, thereby increasing the moment of inertia.
Thus I₁ω₁ = I₂ω₂ = L = constant.

An acrobat: In the coiled position of the body, the moment of inertia decreases and this helps the acrobat perform 2 or 3 somersaults before gravity takes over. In the stretched position moment of inertia increases and almost the turning effect becomes zero.

Question 16.
Mention the uses of polar satellites?
Answer:

• Polar satellites can view polar and equatorial regions at close distances with good resolutions.
• Polar satellites are used for remote sensing, meteorology and environmental studies of the Earth.

Question 17.
State and explain zeroth law of thermodynamics.
Answer:
If two thermodynamic systems are in thermal equilibrium with third individually, then the systems are said to be in mutual thermal equilibrium with each other.
If T_A = T_C , T_B = T_C then T_A = T_B. where ‘T’ represents the temperatures and A, B, C represent the thermodynamic systems.

Question 18.
On an average a human heart is found to beat 75 times in a minute. Calculate its frequency and time period.
Answer:
No. of beats = 75
Time taken = 1 minute = 60 second

Part – C

III. Answer any FIVE of the following questions: ( 5 × 3 = 15 )

Question 19.
State and explain triangle law of vector addition.
Answer:
If two vectors are represented by the two sides of a triangle taken in order then their resultant is represented by the closing side in the opposite order.

Question 20.
Prove that for a particle in rectilinear motion under constant acceleration, the change in kinetic energy of the particle is equal to the work done on it by the net force?
Answer:
The difference of PE. or K..E. required by a body at two different positions is equal to the amount of work done.
\(\int_{k_{i}}^{k_{i}} d(K E)=\frac{1}{2} m\left(v^{2}-u^{2}\right)\)
= mas = Fs
= work done
i. e. W = K_f – K_i.

Question 21.
Draw the stress verses strain graph for a metallic wire stretched up to fracture point. Define the terms proportional limit and fracture point.
Answer:
Statement: The ratio of stress to strain is a constant for a material within the elastic limit.Modulus of elasticity = \(\frac{\text { Stress }}{\text { Strain }}\)

Within the elastic limit, stress v/s strain is a straight line ‘A’ is the elastic limit upto which Hooke’s law is applicable. Beyond ‘B’ the yielding point, the wire extends but does not return to the initial state when the deforming force is removed. ‘F’ is the breaking point. ‘EF’ allows the material to be malleable and ‘DE’, ductile.

Question 22.
Find the torque of a force \(7 \hat{i}+3 \hat{j}-5 \hat{k}\) about the origin. The force acts on a particle whose position vector is \(\hat{i}-\hat{j}+\hat{k}\).
Answer:
\(\overrightarrow{\mathrm{F}}=7 \hat{i}+3 \hat{j}-5 \hat{k} ; \vec{r}=\hat{i}-\hat{j}+\hat{k}\)

∴τ = 15.74 Nm

Question 23.
What is capillary rise? Write an expression for it. Explain the terms.
Answer:
A rise in a liquid above the level of zero pressure due to a net upward force produced by the attraction of the water molecules to a solid surface.

Question 24.
Write any three assumptions of kinetic theory of gases.
Answer:

1. Collisions of molecules on the walls are perfectly elastic.
2. The size of the molecules are neglected when compared to the volume of the container.
3. The contribution to the net pressure due to inter-molecular collisions is neglected.
4. The root mean square value of speed is the average of velocities taken in all the three directions.

Question 25.
State and explain the law of thermal conduction.
Answer:
The quantity of heat conducted during the steady state is directly proportional to the,
(i) Area of cross-section of a conductor.
(ii) Temperature difference between the two points or ends (θ₁ – θ₂).
(iii) Time of passage of heat (t) and inversely proportional to the thickness or distance between the two ends of the conductor (d).
i.e., Q = \(\frac{\mathrm{KA}\left(\theta_{1}-\theta_{2}\right) \mathrm{t}}{\mathrm{d}}\)
where ’K’ is thermal conductivity of the material of the conductor.
The SI unit of thermal conductivity is Wm^-1 K^-1.

Question 26.
Mention any three differences between standing waves and progressive waves.
Answer:

1. Progressive waves transfer energy, whereas stationary waves do not.
   1. No particles of the medium are in a state of rest in a PW but in a SW, the particles at nodes will be at rest.
2. The particle velocities will remain the same for a given displacement in a PW, whereas in a SW, particles at nodes will have zero speed and at antinodes, particles have maximum speed.
3. y = f(x, t) for a PW and y = f(x) g(t) for a SW.
4. Distance between two points at which particles have same state of vibration is called wavelength in a PW whereas distance between two consecutive nodes or antinodes is half the wavelength.

Part – D

IV. Answer any TWO of the following questions : ( 2 × 5 = 10 )

Question 27.
What is velocity – time graph. Derive the equation of motion: v² – v₀² = 2ax.
Answer:
Let ‘v₀’ be the initial velocity of a particle describing uniform accelerated motion ‘a’.
Slope of the line AB = a = tanθ = where BC = v – v₀ and AC = t
i.e., a = \(\frac{v-v_{0}}{t}\) ……….(1)
But area of trapezium = x = 1/2 × OD × (OA + BD)
i.e., x = 1/2 t(v_{0 +} v)

From(1), t = \(\frac{v-v_{0}}{a}\)
Hence (2) may be written as 2s = \(\left(\frac{v-v_{0}}{a}\right)\)(v + v₀)
∴v² – v₀² = 2ax.

Question 28.
Derive the expression for maximum safe speed of a vehicle on a banked road in circular motion.
Answer:
From the figure, ‘θ’ is the angle of elevation of outer edge over the inner edge. ‘R’ is the normal reaction force.

R sinθ = \(\frac{m v^{2}}{r}\)………(1)
Rcosθ = mg  ………(2)
(1) ÷ (2) gives
tanθ = \(\frac{v^{2}}{r g}\)
∴v_max = \(=\sqrt{r g \tan \theta}\)

Question 29.
What is elastic collision? Obtain the expression for final velocities of two bodies undergoing elastic collision in one dimension.
Answer:
A collision in which linear momentum and kinetic energy of the interacting system are conserved, is known as an elastic collision.
From the law of conservation of linear momentum,
m₁ v_1i + m₂ v_2i = m₁v_1f + m₂v_2f ……….(1)
From the law of conservation of total kinetic energy,
\(\frac{1}{2} m_{1} v_{1 i}+\frac{1}{2} m_{2} v_{2 i}=\frac{1}{2} m_{1} v_{1 f}^{2}+\frac{1}{2} m_{2} v_{2 f}^{2}\)….(2)

V. Answer any TWO of the following questions: ( 2 × 5 = 10 )

Question 30.
What is escape speed? Obtain the expression for escape speed. What is the value of escape speed for earth?
Answer:
It is the minimum speed needed for a free object to escape from the gravitational influence of a massive body.
For a satellite to escape into infinite orbit,
∆PE = PE_∞ – PE_r  ∵PE_∞ = 0
But K.E = PE.
∆PE = \(-\left(-\frac{\mathrm{GMm}}{\mathrm{R}+\mathrm{h}}\right)\)

It is assumed that at infinite distance PE = 0, v₁ = 0.
It is a free fall of an object from the point of infinity to a point on the surface in the absence of any frictional forces.

Question 31.
What is isothermal process? Obtain the expression for work done in an isothermal process.
Answer:
The process in which changes in pressure and volume of a gas system takes place at constant temperature of the system, is known as isothermal process.
For an isothermal process, PV = constant.
At any intermediate stage with pressure P and change in volume from V to V + dV,
Work done dW = P dV. However for the entire process W = \(=\int_{V_{1}}^{V_{2}}\)PdV.

For V₂ > V₁, W > 0 and for V₂ < V₁, W < 0.
In an isothermal expansion, the gas absorbs heat and does work, while in an isothermal compression, work is done on the gas by the environment and heat is released.

Question 32.
What is simple harmonic motion? Derive an expression for velocity and acceleration in simple harmonic motion.
Answer:
A SHM is the simplest form of oscillatory motion in which the force on the oscillating particle or body is directly proportional to the displacement from the mean position and the force directed towards the mean position.
We know that, the displacement of the particle
y = A sin ωt
But v = \(\frac{d y}{d t}\)
∴v = \(\frac{d}{d t}\)(A sin ωt)
and acceleration,
a = \(\frac{d v}{d t}\)
∴a = \(\frac{d}{d t}\)(Aω cos ωt)
a = -ω² A sin ωt

VI. Answer any THREE of the following questions : ( 3 × 5 = 15 )

Question 33.
A cricketer can throw a ball to a maximum horizontal distance of 100 m..How much high above the ground can the cricketer throw the same ball? And for how long the bail remains in the air in this case?
Answer:
R = 100 m
R_max = \(\frac{v^{2}}{g}\)    θ = 45°
∴v² = R_max x g
v² = 100 × 9.8
v² = 980 m²s^-2 and v = 31.3 ms^-1
∴the maximum height can be calculated, by

T = 4.52s

Question 34.
A stone of mass 0.25 kg tied to the end of a string is whirled round in a circle of radius 1.5 m with a speed of 40 rev./min in a horizontal plane. What is the tension in the string? W hat is the maximum speed with which the stone can be whirled around if the string can withstand a maximum tension of 200 N?
Answer:

T_max = \(\frac{m v^{2}}{r}\)
T_max = mrω² [v = rω]
= 0.25 x 1.5 x \(\left(\frac{4 \pi}{3}\right)^{2}\)
As the string can withstand a maximum tension of 200 N.
T_max = \(\frac{m v_{\max }^{2}}{r}\)
T_max = \(\frac{T_{\max } \times r}{m}\)

Question 35.
A solid cylinder of mass 20 kg rotates about its axis with angular speed 100 rad s^-1. The radius of the cylinder is 0.25 m. What is the kinetic energy associated with the rotation of the cylinder? Calculate the magnitude of angular momentum of the cylinder about its axis.
Answer:
m = 20 kg
w =100 rad/s
r = 0.25 m
(i) The moment of inertia of the solid cylinder,
I = \(\frac{m r^{2}}{2}\) = \(\frac{1}{2}\) × 20 × (0.25)
I = 0.625 kgm²
(ii) The kinetic energy of rotation, KE = \(\frac{1}{2} \mathrm{I} \omega^{2}\)
KE \(=\frac{1}{2} \mathrm{I} \omega^{2}=\frac{1}{2} \times 0.625 \times(100)^{2}\)
K.E = 3125J
(iii) Angular momentum,
L = Iω
i.e.,L = 0.625 × 100
L = 62.5 Js

Question 36.
A brass rod of length 50 cm and diameter 3.0 mm is joined to a steel rod of the same length and diameter. What is the change in length of the combined rod at 250° C if the original lengths arc at 40.0° C? Is there a ‘thermal stress’ developed at the junction? The ends of the rod are free to expand.
(Co-efficient of linear expansion of brass = 2.0 × 10⁵ K^-1 , steel = 1.2 × 10^-5 K^-1).
Answer:
T₁ = 40°C, T₂ = 250°C
∴∆T = 210°C
For brass rod, initial length (L₀) = 50 cm
Let final length = L
α_b = 2 × 10^-5 /K
L = L₀ (1 + α_b ∆T) = 50 (1 + 2 × 10^-5 × 210) = 50(1 + 420 × 10^-5)
L = 50.21 cm
∴Increase in length (∆L) = L – L₀ = 50.21 – 50
∆L = 0.21 cm
For steel rod,
Initial length (L₀¹) = 50 cm
Let final length = L¹
α_s =1.2 × 10^-5 K^-1
∴L¹ = L₀¹ (1 + α_s ∆T) = 50 (1 + 1.2 × 10^-5 × 210) = 50 × 1.00252
L¹ = 50.126 cm
∴increase in length (∆L¹) = 50.126 – 50 = 0.126 cm
∴Total increase in length = ∆L + ∆L¹ = 0.21 + 0.126 = 0.336 cm

Question 37.
A wave travelling along a string is described by, y (x, t) = 0.005 sin (80.0 × – 3.0 t), in which the numerical constants are in St units (0.005 m, 80.0 rad m^-1, and 3.0 rad s^-1). Calculate (a) the amplitude, (b) the wavelength, and (c) the frequency of the wave. Also, calculate the displacement jr of the wave at a distance x = 30.0 cm and time t = 20 s?
Answer:
The given equation is in the form
y = A sin (kx – wt)
∴A = 0.005 m,  ω = 3rads^-1

y (x, t) = -0.005 sin (3.0 t – 80.0 x),
= -5 × 10^-3 sin (80 × 0.3 – 3 × 20)
= 0.713 m

Students can Download 1st PUC Physics Previous Year Question Paper March 2019, Karnataka 1st PUC Physics Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

Karnataka 1st PUC Physics Previous Year Question Paper March 2019

Mangalore District
First PUC Annual Examination, March 2019

Time : 3.15 Hours
Maximum Marks: 70

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I Answer the following questions. ( 10 × 1 = 10 )

Question 1.
Name the system of units accepted internationally.

Question 2.
Define null vector.

Question 3.
Give on example for conservative force.

Question 4.
Write an expression for moment of inertia of a solid sphere of radius R and mass M about its diameter.

Question 5.
Define angular acceleration

Question 6.
What is meant by elasticity of a body?

Question 7.
How does the fractional change in length of a rod varies with its change in temperature?

Question 8.
State zeroth law of thermodynamics

Question 9.
Define mean free path of a gas molecule.

Question 10.
What is a node in stationary waves?

Part – B

II. Answer any FIVE of the following Questions. ( 5 × 2 = 10 )

Question 11.
Name the strongest and weakest fundamental forces in nature.

Question 12.
Write any two applications of dimensional analysis.

Question 13.
Write any two differences between distance and displacement.

Question 14.
Mention any two factors on which the centripetal acceleration depends.

Question 15.
How does the linear momentum of a body varies with its mass and velocity?

Question 16.
State Pascal’s law. Name any one device which works on the principle of Pascal’s law.

Question 17.
State and explain Boyle’s law.

Question 18.
What is periodic motion? Give an example.

Part – C

III. Answer any FIVE of the following questions. ( 5 × 3 = 15 )

Question 19.
Explain triangle method of addition of two vectors.

Question 20.
Write any three advantages of friction

Question 21.
Define work done by a force. Under what conditions the work done by a force is maximum and minimum?

Question 22.
When does the rigid body is said to be in mechanical equilibrium? Write the conditions for the equilibrium of a rigid body.

Question 23.
Derive an expression for acceleration due to gravity on the surface of the earth in terms of mass of the earth and gravitational constant.

Question 24.
State and explain Hook’s law and hence define modulus of elasticity.

Question 25.
What is meant by viscosity? How does the viscosity change with rise of temperature in case of (i) liquids and
(ii) gases?

Question 26.
What is radiation? Mention any two properties of thermal radiations.

Part – D

IV. Answer any TWO of the following Questions. ( 2 × 5 = 10 )

Question 27.
What is meant by velocity – time graph? Derive the equation x = v₀t + \(\frac{1}{2}\) at² from velocity – time graph

Question 28.
Define elastic potential energy. Derive an expression for potential energy of a spring.

Question 29.
Derive an expression for kinetic energy of a rolling body.

V. Answer any TWO of the following questions. ( 2 × 5 = 10 )

Question 30.
Explain the working of Carnot engine with the help of PV diagram.

Question 31.
Derive an expression for time period of oscillation of a simple pendulum

Question 32.
Show that only odd harmonics are present in vibrations of air column in closed pipe.

VI. Answer any THREE of the following questions. ( 3 × 5 = 15 )

Question 33.
A Cricket ball is thrown at a speed of 28 ms^-1 in the direction 30° above the horizontal. Calculate (a) maximum
height reached by the projectile and (b) horizontal range of the projectile. (Given: Acceleration due to gravity = 9.8 ms^-2)

Question 34.
A constant force acting on a body of mass 3.0 kg changes its speed from 2.0 ms^-1 to 3.5 ms^-1 in 25 second. If the direction of the motion of the body remains unchanged, find the magnitude and direction of the force?

Question 35.
An artificial satellite revolves around the earth with an orbital velocity of 5.92 kms^-1. Calculate height of the satellite from the earth’s surface. (Given: Radius of the earth = 6380 km Acceleration due to gravity of earth = 9.8 ms^-2).

Question 36.
A copper block of mass 2.5 kg is heated in a furnace to a temperature of 500°C and then placed on a large ice block at a temperature of 0°C. Calculate the maximum amount of ice that can melt? (Given: Specific he: t of copper = 390 Jkg^-1k^-1 Latent heat of fusion of ice = 3.35 × 105 Jkg^-1)

Question 37.
A transverse harmonic wave travelling along positive X-axis on a stretched string is described by Y(x, t) = 0.03 sin(36t – 1.8x + \(\frac{\pi}{4}\)) where X and Y are in metre and t is in second. Calculate (a) amplitude (b) initial phase (c) frequency and (d) speed of the wave.

Bangalore North District
First PUC Annual Examination, March 2019

Time : 3.15 Hours
Maximum Marks: 70

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer the following questions. ( 10 × 1 = 10 )

Question 1.
How many kilograms in one unified atomic mass unit?

Question 2.
State the law of triangle of addition of two vectors.

Question 3.
State Aristotle’s fallacy.

Question 4.
Name the type of energy stored in a stretched or compressed spring.

Question 5.
Give an example for Torque or Moment of couple.

Question 6.
Write the aim of Cavendish experiment in Gravitation.

Question 7.
How does strain depends on stress?

Question 8.
Mention the value of steam point of water in Fahrenheit scale.

Question 9.
Which quantity is kept constant in Adiabatic process.

Question 10.
The function y = log(ωt). The displacement y increases monotonically with time t, is it periodic function or Non periodic function.

Part – B

II. Answer any FIVE of the following Questions. ( 5 × 2 = 10 )

Question 11.
Name any two fundamental forces in nature.

Question 12.
Define accuracy in the measurement. How does accuracy depends on precision in the measurement?

Question 13.
Distinguish between speed and velocity.

Question 14.
State and explain Newton’s first law of motion.

Question 15.
Mention the relation between linear momentum and angular momentum with usual meanings.

Question 16.
Write any two practical applications of Pascal’s law.

Question 17.
Give any two Assumptions of Kinetic theory of gases.

Question 18.
How does the period of oscillation of a pendulum depends on mass of the bob and length of the pendulum.

Part – C

III. Answer any FIVE of the following questions. ( 5 × 3 = 15 )

Question 19.
Deduce the expression for Horizontal range of a projectile and for what angle of projection horizontal range becomes maximum?

Question 20.
Write any three laws of friction.

Question 21.
Deduce the work-energy theorem for a constant force.

Question 22.
Discuss the motion of centre of mass.

Question 23.
Name the three types of moduli of elasticity.

Question 24.
What is capillary rise? Write the expression for height of capillary rise in the capillary tube with usual meanings.

Question 25.
Obtain the expression for Thermal stress.

Question 26.
Show that the specific heat capacity of a solid is equal to three times that of Gas constant.
[C = 3R]

Part – D

IV. Answer any TWO of the following Questions. ( 2 × 5 = 10 )

Question 27.
What is velocity – time graph? Deduce x = v₀t + \(\frac{1}{2}\) at² by using velocity-time graph.

Question 28.
State and illustrate the law of conservation of linear momentum for any two colliding particles in a closed system.

Question 29.
State and explain parallel axes and perpendicular axes theorems of moment of inertia.

V. Answer any TWO of the following questions. ( 2 × 5 = 10 )

Question 30.
State and explain the laws of thermal conductivity and hence mention the SI Unit of coefficient of thermal conductivity.

Question 31.
Deduce the expression for energy stored in a body executing simple harmonic motion.

Question 32.
Discuss the mode of vibration of air columns in a closed pipe and hence define the fundamental frequency of vibration.

VI. Answer any THREE of the following questions. ( 3 × 5 = 15 )

Question 33.
A stone of mass 0.25 kg tied to the end of a string is whirled round in a circle of radius 1.5 m with a speed of 40 revolutions per minute in a horizontal plane. What is the tension in the string?

Question 34.
A pump on the ground floor a building can pump up water to fill a tank of volume 30 m³ in 15 minutes. If the tank is 40 m above the ground and efficiency of the pump is 30%. How much of electrical power is consumed by the pump?

Question 35.
If two spheres of equal masses with their centres 0.2 m apart attract each other with a force of 1 x 10^-6 kg wt. What should be the value of their masses?
Given : g = 9.8 ms^-2 and G = 6.67 × 10^-11 Nm² kg^-2.

Question 36.
The sink in Carnot’s heat engine is at 300 K and has efficiency 0.4. If the efficiency of the engine is to be increased to 0.5. Find by how many Kelvin the temperature of the source should be increased.

Question 37.
A train is moving at a speed of 72 Kmph towards a station sounding a whistle of frequency 640 Hz. What is the apparent frequency of the whistle as heard by a man standing on the platform when train approaches to him.
Given : Speed of sound = 340 ms^-1.

Bangalore South District
First PUC Annual Examination, March 2019

Time : 3.15 Hours
Maximum Marks: 70

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer the following questions. ( 10 × 1 = 10 )

Question 1.
Write the dimensional formula for force.

Question 2.
Write SI unit of power.

Question 3.
What is Projectile motion?

Question 4.
Write relation between angular velocity and linear velocity.

Question 5.
Write expression for acceleration due to gravity at a height h from the surface of earth.

Question 6.
Define stress.

Question 7.
Define angle of contact.

Question 8.
Write ideal gas equation for one mole of gas.

Question 9.
State zeroth law of thermodynamics.

Question 10.
State law of equipartition of energy.

Part – B

II. Answer any FIVE of the following Questions. ( 5 × 2 = 10 )

Question 11.
Name any two fundamental forces in nature.

Question 12.
Write any two applications of dimensional analysis.

Question 13.
A body gets displacement of 5m in 2s. What is the average velocity?

Question 14.
Define scalar product of two vectors.

Question 15.
What is kinetic friction? Write the expression.

Question 16.
Define specific heat capacity of a substance.

Question 17.
Write any two difference between isothermal process and adiabatic process.

Question 18.
Define frequency and period of oscillation.

Part – C

III. Answer any FIVE of the following questions. ( 5 × 3 = 15 )

Question 19.
A body moving in uniform circular motion, Derive centripetal acceleration a_e = \(\frac{v^{2}}{r}\).

Question 20.
State Newton’s second law of motion. Hence derive F = ma.

Question 21.
State work energy theorem with proof.

Question 22.
Show that kinetic energy of rotating body is \(\frac{1}{2}\) Iω².

Question 23.
State Kepler’s laws of planetory motion.

Question 24.
Calculate \(\frac{C_{p}}{c_{v}}\) for monatomic gas.

Question 25.
Write stress-strain curve for a metal. What is proportional limit and yield point.

Question 26.
State Bernoulli’s theorem and write the equation.

Part – D

IV. Answer any TWO of the following Questions. ( 2 × 5 = 10 )

Question 27.
Derive the equation x = v₀t + \(\frac{1}{2}\) at² using v-t graph.

Question 28.
State and explain law of conservation of momentum with proof.

Question 29.
State and explain parallel axis and perpendicular axis theorem.

V. Answer any TWO of the following questions. ( 2 × 5 = 10 )

Question 30.
Explain working of Carnot’s heat engine.

Question 31.
Derive an expression for energy of a body which is in S.H.M.

Question 32.
What is Doppler effect of sound? Derive expression for apparent frequency of sound when source is moving away from stationary listener.

VI. Answer any THREE of the following questions. ( 3 × 5 = 15 )

Question 33.
A body is projected by making an angle 30° with horizontal with a velocity of 39.2 ms^-1. Find
A. Time of flight (T)
B. Range (R)
C. Maximum height (H)

Question 34.
A body of mass 5 kg moving with a velocity of 6 ms^-1 collide with another body of mass 2 kg which is at rest. After wards they move in the same direction as before. If the velocity of the body of mass 2 kg is 10 ms^-1. find the velocity and kinetic energy of the body of mass 5 kg.

Question 35.
Find the potential energy of a system of four particles each of mass 5 kg placed at the vertices of a square of side 2m.

Question 36.
Two identical bars each of length L = 0.1 m and area A = 0.02 m². One is iron of thermal conductivity K₁ = 79 W m^-1 K^-1 and another of brass of thermal conductivity K₂ = 109 W m^-1 K^-1 are soldered end to end. Free end of iron bar is at 373K and of brass bar is at 273K. Find the temperature at junction of two bars.

Question 37.
A wave travelling in a string is described by an equation y(x, t) = 0.005 sin (80x – 3t) all are in SI unit. Find
a) amplitude (A)
b) Wave length (λ)
c) Period (T)

Dharwad District
First PUC Annual Examination, February 2019

Time : 3.15 Hours
Maximum Marks: 70

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer the following questions. ( 10 × 1 =10 )

Question 1.
Define acceleration.

Question 2.
What does slope of velocity – time graph represent?

Question 3.
For what angle of projection, does the range of a projectile is maximum?

Question 4.
Stale Work – Energy theorem.

Question 5.
Mention an expression for moment of inertia of a thin, circular ring of radius ‘R’ and mass ‘M’ about an axis passing through its diameter.

Question 6.
Mention the value of universal gravitational constant.

Question 7.
Of rubber and steel, which is more elastic?

Question 8.
What happens lo viscosity of a liquid, when it is heated?

Question 9.
State first law of thermodynamics.

Question 10.
Mention the number of degrees of freedom of a mono atomic gas.

Part – B

II. Answer any FIVE of the following Questions. ( 5 × 2 = 10 )

Question 11.
Mention any two basic forces in nature.

Question 12.
A pebble of mass 0.05 kg is thrown vertically upwards. Give the direction of the net force on the pebble
(a) During its upward motion (b) During its downward motion

Question 13.
Mention the conditions for equilibrium of a rigid body.

Question 14.
State and explain Newton’s law of gravitation.

Question 15.
Distinguish between heat capacity and specific heat capacity.

Question 16.
Convert 100°C into Fahrenheit temperature.

Question 17.
Define period and frequency of oscillation.

Question 18.
Distinguish between longitudinal waves and transverse waves.

Part – C

III. Answer any FIVE of the following questions. ( 5 × 3 = 15 )

Question 19.
Check the correctness of an equation V – V₀ = at using dimensional analysis (symbols have usual meaning).

Question 20.
Mention any three advantages of friction.

Question 21.
Derive an expression for potential energy of a stretched spring.

Question 22.
Explain law of conservation of angular momentum in case of a person sitting in a rotating chair.

Question 23.
Define Young’s modulus. Mention an expression for Young’s modulus of a wire and explain the symbols used.

Question 24.
Derive an expression for liquid pressure at a point inside the liquid.

Question 25.
State and explain Dalton’s law of partial pressures.

Question 26.
Mention Newton’s formula for speed for sound in gases and explain Laplace’s connection to Newton’s formula.

Part – D

IV. Answer any TWO of the following Questions. ( 2 × 5 = 10 )

Question 27.
Derive x = v₀t + \(\frac{1}{2}\) at² using velocity – time graph.

Question 28.
Derive an expression for centripetal acceleration.

Question 29.
State and verify law of conservation of linear momentum in case of a system of two bodies.

V. Answer any TWO of the following questions. ( 2 × 5 = 10 )

Question 30.
What is meant by acceleration due to gravity? Derive an expression for variation of acceleration due to gravity with height from earth’s surface.

Question 31.
What is heat engine? With schematic diagram, explain the parts of heat engine.

Question 32.
Derive an expression for total energy in simple harmonic motion.

VI. Answer any THREE of the following questions. ( 3 × 5 = 15 )

Question 33.
A cricket ball is thrown at a speed of 50 ms^-1 in a direction making an angle 30° with the horizontal, calculate time of flight and maximum height. (Given y = 9.8 ms^-2)

Question 34.
A pump on the ground floor of a building can pump up water to fill a tank of volume 30m³ in 15 minutes. If the tank is 40 m above the ground and the efficiency of the pump is 30%. How much electric power is consumed by the pump? (Density of water is 10³ kg m^-3)

Question 35.
The angular speed of a motor wheel is increased from 1200 rpm to 3120 rpm in 16 seconds.
(i) What is its angular acceleration?
(ii) How many revolutions does the wheel make during this time?

Question 36.
A body cools from 80°C to 50°C in 5 minutes. Calculate the time it takes to cool from 60°C to 30°C. The temperature of the surrounding is 20°C.

Question 37.
A train, standing at die outer signal of a railway station blows a whistle of frequency 400 Hz in still air. What is the frequency of the whistle for a platform observer when die train
(a) Approaches the platform with a speed of 10 ms^-1.
(b) Recedes from the platform with a speed of 10 ms^-1
(c) What is the speed of sound in each case? Speed of sound in still air can be taken as 340 ms^-1.

Mysore District
First PUC Annual Examination, February 2019

Time : 3.15 Hours
Maximum Marks: 70

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer the following questions. ( 10 × 1 = 10 )

Question 1.
Write the dimensional formula for Pressure.

Question 2.
When does the circular motion become uniform?

Question 3.
What is the amount of work done by the gravitational force on the body moving on the horizontal plane?

Question 4.
What is elastic collision?

Question 5.
Give one example for elastomers.

Question 6.
What is thermal stress?

Question 7.
Define mean free path of the molecule in the gas.

Question 8.
Where does Kinetic energy of the oscillating particle become maximum?

Question 9.
What is resonance?

Question 10.
Give the value of phase difference between the particles of adjacent loop of stationary wave.

Part – B

II. Answer any FIVE of the following Questions. ( 5 × 2 = 10 )

Question 11.
Name any two fundamental forces of nature.

Question 12.
Mention any two sources of systematic error.

Question 13.
Draw position time graph for the particle having zero acceleration.

Question 14.
Write the equation for maximum horizontal range in projectile motion and explain the terms.

Question 15.
Mention any two methods of reducing friction.

Question 16.
Mention the conditions for the body in mechanical Equilibrium.

Question 17.
State and explain Hooke’s law.

Question 18.
What are extensive thermo dynamical variables? Give one example.

Part – C

III. Answer any FIVE of the following questions. ( 5 × 3 = 15 )

Question 19.
Obtain the equation for maximum height in projectile motion.

Question 20.
Derive \(\overrightarrow{\boldsymbol{F}}=m \overrightarrow{\boldsymbol{a}}\) with usual notations.

Question 21.
Prove the work-energy theorem in the case of constant force.

Question 22.
Obtain the equation for moment of couple.

Question 23.
Derive equation for acceleration clue to gravity on the surface of the earth.

Question 24.
Show that volume co-efficient of expansion of ideal gas is inversely proportional to absolute temperature.

Question 25.
Show that C_v = \(\frac{3}{2}\) R for mono atomic gas.

Question 26.
Give any three differences between progressive wave and stationary wave.

Part – D

IV. Answer any TWO of the following Questions. ( 2 × 5 = 10 )

Question 27.
Derive equation for centripetal acceleration.

Question 28.
Prove “law of conservation of mechanical energy” for freely falling body.

Question 29.
Obtain equation for Kinetic energy of rolling motion.

V. Answer any TWO of the following questions. ( 2 × 5 = 10 )

Question 30.
State and prove Bemaulli’s theorem.

Question 31.
What is isothermal process? Obtain equation for work done in isothermal process.

Question 32.
What is closed pipe? Show that modes of vibration in closed pipe are odd harmonics.

VI. Answer any THREE of the following questions. ( 3 × 5 = 15 )

Question 33.
A Car moving along a straight road with speed of 144 Kmh^-1 is brought to a stop within a distance of 200 m. What is the retardation of the car and how long does it take to come to rest?

Question 34.
A circular racetrack of radius 200 m is banked at the angle of 10°. If the coefficient of friction between the wheels of race car and the road is 0.15, what is the
a) optimum speed of the race car to avoid wear and tear on its tyres?
b) maximum permissible speed to avoid slipping? [Given : Acceleration due to gravity on the earth = 9.8 ms-2]

Question 35.
If the weight of a 4 kg mass on the surface of the earth is 39.2 N, calculate the acceleration due to gravity of earth at
a) 32 km height from the surface of the earth.
b) 16 km depth from the surface of the earth. [Given : Radius of earth = 6400 km]

Question 36.
A copper block of mass 2.5 kg is heated in a furnace to a temperature of 500°C and then placed on a large ice block. What is the maximum amount of ice that can melt?
(Given: Specific heat of copper = 0.39 × 10³ Jkg^-1K^-1 Latent Heat of fusion of water = 335 x 10³ Jkg^-1)

Question 37.
A body oscillates with SHM according to the equation (in SI units)
x = 5 cos (3πt + \(\frac{\pi}{4}\))
Calculate:
(a) frequency of oscillation
(b) amplitude of oscillation
(c) Displacement of oscillation at t= 1s

Belgaum District
First PUC Annual Examination, March 2019

Time : 3.15 Hours
Maximum Marks: 70

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer the following questions. ( 10 × 1 = 10 )

Question 1.
Write the number of significant figures in 287.5 m.

Question 2.
Give example for a vector multiplied by scalar.

Question 3.
When work done is said to be maximum?

Question 4.
Which law of motion is used to explain rocket propulsion?

Question 5.
Write S. I. unit of moment of inertia.

Question 6.
Which is more elastic, rubber or steel?

Question 7.
Define coefficient of volume expansion in solids.

Question 8.
State Zeroth law of thermodynamics.

Question 9.
How many degrees of freedom are there in diatomic gases?

Question 10.
What is Doppler’s effect?

Part – B

II. Answer any FIVE of the following Questions. ( 5 × 2 = 10 )

Question 11.
Name any two basic forces in nature.

Question 12.
Mention any two uses of dimension analysis.

Question 13.
Draw velocity time graph of
a) a body starting from rest and moving with uniform acceleration.
b) a body moving with uniform negative acceleration.

Question 14.
Mention the expression for magnitude of two vectors and explain terms.

Question 15.
What is the importance of centre of mass of system of particles?

Question 16.
Define Poisson’s ratio and write the formula for it.

Question 17.
What is meant by streamline flow and turbulent flow?

Question 18.
What are damped oscillations? Give one example.

Part – C

III. Answer any FIVE of the following questions. ( 5 × 3 = 15 )

Question 19.
Obtain an expression for range of a projectile.

Question 20.
Mention types of friction.

Question 21.
Distinguish between elastic and inelastic collision.

Question 22.
State and explain the theorem of perpendicular axes.

Question 23.
Derive, the relation between acceleration due to gravity and gravitational constant.

Question 24.
Arrive at an expression for pressure inside a liquid.

Question 25.
What is latent heat? On what factors does it depend? Give its S.I. unit.

Question 26.
State the assumptions of kinetic theory of gases.

Part – D

IV. Answer any TWO of the following Questions. ( 2 × 5 = 10 )

Question 27.
Define centripetal acceleration and obtain expression for it

Question 28.
State Newton’s second law of motion and hence derive F = ma where symbols have usual meanings.

Question 29.
Define torque show that torque equal to the rate of change of angular momentum of particle.

V. Answer any TWO of the following questions. ( 2 × 5 = 10 )

Question 30.
State and explain the Newton’ s law of cooling.

Question 31.
Derive expression for frequency and time period of oscillatory bob of simple pendulum.

Question 32.
Explain modes of vibration of air column in closed Pipe.

VI. Answer any THREE of the following questions. ( 3 × 5 = 15 )

Question 33.
A player throws a ball upwards with an initial speed of 29.4 ms^-1.
a) What is the velocity at the highest point of its path?
b) To what height does the ball rise and after how long does the ball return to the player’s hands?
Take g = 9.8 ms^-2 Neglect air resistance.

Question 34.
A pump on ground floor of building can pump up water to fill a tank of volume 30 m³ in 15 minutes. If tank is 40m above the ground and efficiency of pump is 30%, how much electric power is consumed by the pump. Take g = 9.8ms^-2, ρ= 1000 kgm^-3.

Question 35.
Calculate the acceleration due to gravity
a) at height 16 km above the earth’s surface and
b) at depth 12.8 km below the surface of earth,
Given radius of earth is 6400 km acceleration due to gravity on the surface of earth = 9.8 ms^-2.

Question 36.
A Carnot’s engine whose efficiency is 30% takes heat from a source maintained at temperature of 600 K of it desired to have an engine of efficiency 50%; What should be the intake temperature for same exhaust (sink)?

Question 37.
A progressive wave described by Y(x, t) = 0.005 sin(80πt – 3πx) where x, y are in metre and ‘t’ is in second. Find the (a) amplitude (b) wave length (c) period and frequency of wave.

Students can Download 1st PUC Physics Previous Year Question Paper March 2018, Karnataka 1st PUC Physics Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

Karnataka 1st PUC Physics Previous Year Question Paper March 2018

Bangalore North District
First PUC Annual Examination, March 2018

Time : 3.15 Hours
Maximum Marks: 70

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer ALL the following questions ( 10 × 1 = 10 )

Question 1.
What are fundamental units?

Question 2.
Define centripetal acceleration.

Question 3.
When is work done by the force positive?

Question 4.
Express torque in vector form.

Question 5.
Give the relation between stress and strain.

Question 6.
State Pascal’s Law.

Question 7.
What is magnus effect?

Question 8.
Define heat capacity.

Question 9.
Mention the formulae for coefficient of performance of a refrigerator.

Question 10.
Define mean free path.

Part – B

II Answer any FIVE of the following questions. ( 5 × 2 = 10 )

Question 11.
Mention two fundamental forces in nature.

Question 12.
Write the dimensional formulae for a) Force b) Pressure

Question 13.
Define displacement and acceleration.

Question 14.
Give the representation for scalar product and Vector product of two vectors.

Question 15.
Mention any two methods of reducing friction. .

Question 16.
Write the general conditions for equilibrium of a rigid body.

Question 17.
Explain the application of surface tension idea in case of action of detergents.

Question 18.
What is simple harmonic motion? Give one example.

Part – C

III. Answer any FIVE of the following questions: ( 5 × 3 = 15 )

Question 19.
Derive an expression for maximum height of a projectile.

Question 20.
What is angle of banking? Mention an expression for maximum safe speed of a vehicle on a level road and express the symbols.

Question 21.
Distinguish between conservative and non conservative forces.

Question 22.
Compare the equations of linear motion with rotational motion.

Question 23.
State Kepler’s laws of planetary motion.

Question 24.
Derive an expression for Young’s modulas of a wire in terms of its radius.

Question 25.
Prove, that α_v = \(\frac{1}{T}\) for ideal gas.

Question 26.
Mention three assumptions of Kinetic theory of gasses.

Part – D

IV. Answer any TWO of the following questions. ( 2 × 5 = 10 )

Question 27.
What is Velocity-time graph? Derive the equation x = v₀t + \(\frac{1}{2}\) at² by graphical method.

Question 28.
State and prove law of conservation of linear momentum.

Question 29.
Define Torque and angular momentum. Derive the relation between torque and angular momentum.

V. Answer any TWO of the following questions. ( 2 × 5 = 10 )

Question 30.
Explain different stages of Carnot’s cycle with P-V diagram.

Question 31.
Derive an expression for time period of oscillating bob of simple pendulum.

Question 32.
Mention the differences between progressive and stationary waves.

VI. Answer any THREE of the following questions: ( 3 × 5 = 15 )

Question 33.
An aircraft executes a horizontal loop of radius 1 Km with a steady speed of 900 Kmph. Compare its centripetal acceleration with acceleration due to gravity.

Question 34.
A man weighing 49 Kg carries a bag of 2 Kg. He climbs to the top of a building 100 m tall in 5 minute. Calculate the work done by the man and the power he develops.

Question 35.
Calculate ‘g’ at the bottom of a mine 8 Km deep and at an altitude 32 Km above the earth’s surface, radius of earth = 6.4 × 10⁶ m and g on earth’s surface = 9.8 m/s².

Question 36.
A cubical ice box of thermocol has each side 30 cm and thickness 5 cm. 4 Kg of ice is put in the box, if outside temperature is 45°C and coefficient of thermal conductivity is 0.01 JS^-1 m^-1 K^-1. Calculate the mass of ice left after 6 hrs. Take latent heat of fusion of ice is 335 × 10¹³ J Kg^-1.

Question 37.
The apparent frequency of a note when an observer moves towards a stationary source with a velocity 20 m/s is 200 Hz. Calculate the actual frequency of a note. Also, Calculate wavelength if Velocity of sound in air is 350 m/s.

Dakshina Kannada District
First PUC Annual Examination, March 2018

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer All questions: ( 10 × 1 = 10 )

Question 1.
Which component of Velocity of a projectile remains constant throughout the time of flight?

Question 2.
State work-energy theorem.

Question 3.
In which type of collision, the two bodies stick together after collision?

Question 4.
What is the total external force on a system of particles when its total momentum remains constant?

Question 5.
Write the relation between escape velocity and orbital velocity of a satellite revolving close to Earth surface.

Question 6.
What is a Venturimeter?

Question 7.
What is the Mode of heat transfer through a solid?

Question 8.
Mention the S.I. unit of Young’s Modulus.

Question 9.
Define specific heat capacity of the substance.

Question 10.
How does average kinetic energy of a gas molecule depend on the absolute temperature?

Part – B

II. Answer any Five of the following questions: ( 5 × 2 = 10 )

Question 11.
Mention the strongest and weakest force among the fundamental forces in nature.

Question 12.
Draw position time graph for a particle moving with:
i) negative velocity
ii) positive acceleration

Question 13.
What is a Projectile? Give an example.

Question 14.
Show that power is equal to the dot product of force and velocity.

Question 15.
Define Radius of Gyration. Write the expression for Moment of Inertia in terms of Radius of Gyration.

Question 16.
State Kepler second law and third law of Planetary motion.

Question 17.
Suggest two methods of reducing friction. ,

Question 18.
At where is kinetic energy of a particle executing SHM:
(i) Maximum and
(ii) Minimum

Part – C

III. Answer any Five of the following questions: ( 5 × 3 = 15 )

Question 19.
Using the principle of homogeneity of dimensions, check the dimensional consistency of the equation.
T² = \(\frac{4 \pi^{2} r^{3}}{G M}\) where, T is time period , G is gravitational constant, M is mass and r is orbital radius.

Question 20.
Obtain an expression for time of flight of a Projectile.

Question 21.
What is Static Friction? State laws of Static Friction.

Question 22.
State and explain theorem of perpendicular axes applicable to a planar body.

Question 23.
Draw a typical stress-strain curve for a metal. Hence, locate:
(i) yield point
(ii) fracture point

Question 24.
Distinguish between streamline flow and turbulent flow.

Question 25.
Deduce α_v = \(\frac{1}{T}\) for an ideal gas with usual notation.

Question 26.
What is a degree of Freedom? Mention the number of degrees of freedom of a monoatomic and diatomic gas molecule.

Part – D

IV. Answer any Two of the following questions: ( 2 × 5 = 10 )

Question 27.
Using velocity time graph, derive v² = v₀²+ 2ax, where the symbols have their usual significance.

Question 28.
State Newton second law of Motion. Hence, derive \(\vec{F}=m \vec{a}\).

Question 29.
Define angular momentum of a particle. Prove that the time rate of change of angular momentum is equal to torque acting on the particle.

V. Answer any Two of the following questions: ( 2 × 5 = 10 )

Question 30.
What is Thermal Radiation? List four properties of Thermal Radiation.

Question 31.
Derive an expression for Time period and hence frequency of an oscillating Simple Pendulum.

Question 32.
What is an Open Pipe? Discuss the modes of vibration of the air column in an open pipe.

VI. Answer any Three of the following questions: ( 3 × 5 = 15 )

Question 33.
A football player kicks a ball at a distance 10 m from a vertical pole at an angle of 45°. The ball just clears the tip of the pole and falls at a distance of 10 m on the other side. Determine the height of the vertical pole.

Question 34.
A Car weighing 900 Kg moving with a velocity of 20 ms^-1 is uniformly accelerated with an acceleration of 2ms^-2 for 10 second. Calculate the work done and the force required to accelerate the Car.

Question 35.
An artificial satellite revolves round the Earth at a height 700 km from the surface. Calculate its:
(i) Kinetic energy
(ii) Potential energy
(iii) Total energy
Given : Mass of satellite = 150 Kg
Mass of the Earth = 6 × 10²⁴ Kg
Radius of the Earth = 6,400 Km.

Question 36.
A heat engine absorbs 2 kJ of heat from a reservoir at 150°C and rejects 0.5 kJ of heat to a sink in one complete cycle. Calculate:
(i) Efficiency of the Engine.
(ii) Temperature of the sink.
(iii) Work done by the heat engine during each cycle.
(iv) Efficiency of the engine if the temperature of the sink is further decreased by 50K.

Question 37.
A train moving at a speed of 30 ms^-1 approaches a station and sounds a horn of frequency 500 Hz. What is the apparent frequency of the horn as heard by a man on the platform as the train approaches him. Calculate the change in frequency as heard by the Man.
Given : Speed of Sound = 340 ms^-1

Mysore District
First PUC Annual Examination, March 2018

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer All questions: ( 10 × 1 = 10 )

Question 1.
Who discovered positron?

Question 2.
How many significant figures are there in 0.027 × 10³ m?

Question 3.
What does the slope of x -t graph represent?

Question 4.
Define unit vector.

Question 5.
Express 1k Whr injoules.

Question 6.
What is a rigid body?

Question 7.
Young’s modulus of steel is greater than that of copper. What does it mean?

Question 8.
At which temperature, density of water is maximum.

Question 9.
What is the significance of I-Law of thermo-dynamics?

Question 10.
How does average kinetic energy of a gas molecule depend on it’s temperature?

Part – B

II. Answer any Five of the following questions: ( 5 × 2 = 10 )

Question 11.
Check the correctness of the equation F = \(\frac{m v^{2}}{r}\) dimensionally, where the symbols have usual meaning.

Question 12.
Distinguish between path length and displacement.

Question 13.
What is centripetal acceleration? Write an expression for magnitude of centripetal acceleration.

Question 14.
Write any two methods of reducing friction.

Question 15.
State Pascal’s law of transmission of fluid pressure. Give any one of it’s applications.

Question 16.
Write any two differences between streamline flow and turbulent flow.

Question 17.
Define (a) free vibrations and (b) forced vibrations.

Question 18.
What is Doppler effect? Write the general expression for apparent frequency when both source and the observer are moving in the same direction.

Part – C

III. Answer any Five of the following questions: ( 5 × 3 = 15 )

Question 19.
Obtain the expressions for rectangular components of a given vector \(\vec{A}\) in x – y plane.

Question 20.
What is an impulsive force? Show that impulse of a force is equal to change in momentum.

Question 21.
State and prove work-energy theorem for a constant force.

Question 22.
State Kepler’s laws of planetary motion.

Question 23.
Draw stress versus strain curve for a metal and indicate the points of (a) Yield point, (b) Ultimate tensile strength and (c) Fracture point.

Question 24.
From Newton’s law of cooling, show that log_e(T₂ – T₁)  = -kt + C.

Question 25.
Using the law of equipartition of energy find the value of C_p & C_v for monoatomic gases and hence find their ratio.

Question 26.
Write Newton’s formula for velocity of sound in gases. Explain Laplace’s correction.

Part – D

IV. Answer any Two of the following questions: (2 × 5 = 10 )

Question 27.
What is v-t graph? Derive x = v₀t + \(\frac{1}{2}\) at² by graphical method.

Question 28.
State Newton’s II- law of motion and hence derive \(\vec{F}=m \vec{a}\).

Question 29.
(a) Define radius of gyration.
(b) State and explain the theorems of perpendicular and parallel axes on moment of inertia.

V. Answer any Two of the following questions: ( 2 × 5 = 10 )

Question 30.
State and explain Newton’s law of gravitation. Establish the relation between g and G.

Question 31.
Describe the working of Carnot’s engine using P-V diagram.

Question 32.
Obtain the expression for time period of oscillation of a simple pendulum.

VI. Answer any Three of the following questions: ( 3 × 5 = 15 )

Question 33.
A hiker stands on the edge of a cliff 490 m above the ground and throws a stone horizontally with an initial speed of 15 ms^-1. Neglecting air resistance, find the time taken by the stone to reach the ground and the speed with which it hits the ground.

Question 34.
A body of mass 0.1 kg falling freely under gravity takes 10s to reach the ground. Calculate kinetic energy and potential energy of the body when the body has travelled for 6s.

Question 35.
The angular speed of a motor wheel is increased from 1200 rpm to 3120 rpm in 16 seconds,
(i) What is it’s angular acceleration?
(ii) How many revolutions does the engine make during this time?

Question 36.
Two rods of copper and brass having the same length and cross section are joined end to end. The free end of the copper rod is kept at 273 K and the free end of the brass rod is kept at 373 K. Calculate the temperature of the junction of the two rods at steady state. Assume that thermal conductivity of copper is 4 times that of brass.

Question 37.
A wave travelling along a string is described by Y = 0.005 sin (80x – 3t) in which the numerical constants are in S.I. units. Calculate (a) the amplitude (b) the wave length (c) the period and (d) the frequency of the wave.

Belgaum District
First PUC Annual Examination, March 2018

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer All questions: ( 10 × 1 = 10 )

Question 1.
What are derived units?

Question 2.
Define null vector.

Question 3.
Give an example for inertia of motion.

Question 4.
Mention the expression for the work done by a spring force.

Question 5.
Write the relation between linear velocity and angular velocity .

Question 6.
Why liquid and gas do not posses modulus of rigidity?

Question 7.
State Pascal’s law.

Question 8.
Define specific heat capacity.

Question 9.
Name the working substance used in Carnot cycle.

Question 10.
How many degrees of freedom for a mono atomic gas molecule?

Part – B

II. Answer any Five of the following questions: ( 5 × 2 = 10 )

Question 11.
Name the (i) strongest (ii) weakest fundamental force in nature.

Question 12.
Write the dimensional formula for (i) Force and (ii) Pressure.

Question 13.
Distinguish between distance and displacement.

Question 14.
State and explain the law of triangle of vectors.

Question 15.
What is impulsive force? Give one example.

Question 16.
Define angular momentum. Write the expression for it.

Question 17.
Mention any two methods of transmission of heat.

Question 18.
A particle takes 32 seconds to make 20 oscillations. Calculate time period and frequency.

Part – C

III. Answer any Five of the following questions: ( 5 × 3 = 15 )

Question 19.
Derive the expression for the centripetal acceleration.

Question 20.
What is Friction? What are (a) Static Friction, (b) Limiting Friction.

Question 21.
Prove work – energy theorem for a constant force.

Question 22.
State and explain the parallel axis theorem.

Question 23.
Derive relation between ‘g’ and ‘G’.

Question 24.
State and explain Hooke’s law. Define modulus of elasticity.

Question 25.
Derive an expression for liquid pressure at a point inside the liquid.

Question 26.
Mention any three assumptions of kinetic theory of gases.

Part – D

IV. Answer any Two of the following questions:

Question 27.
What is velocity time graph? Derive the equation of motion X = v₀t + \(\frac{1}{2}\) at² from v-t graph.

Question 28.
State and prove the law of conservation of linear momentum.

Question 29.
What is a rigid body? Derive an expression for the kinetic energy of a rolling body.

V. Answer any Two of the following questions: ( 2 × 5 = 10 )

Question 30.
What is isothermal process? Obtain the expression for work done in isothermal process.

Question 31.
Define simple hormonic motion. Mention the characteristics of simple hormonic motion.

Question 32.
Show that only odd hormonics arc present in the vibrations of air column in a closed pipe.

VI. Answer any Three of the following questions: ( 3 × 5 = 15 )

Question 33.
A cricketer can throw a ball to a maximum horizontal distance of 100 m. How much high above the ground can the cricketer throw the same ball?

Question 34.
A man weighing 48 kg carries a bag of 2 kg. He climbs to the top of a building 100 m tall in 5 minutes. Calculate the work done by the man and his power.

Question 35.
An earth satellite in a circular orbit a height of 200 km above the earth’s surface has a period of 80 minutes. Calculate the mass of the earth from this data, Radius of the earth – 6400 km.

Question 36.
A brass boiler has a base of area 0.16 m² and thickness 1 cm. It boils water at the rate of 6 kg. min^-1 when placed on a gas stove. Estimate the temperature of the part of the flame in contact with the boiler.
Given that: thermal conductivity of brass = 10⁹ JS m^-1t^-1 k^-1 and heat of vapourisation of water = 2256 × 10³ J kg^-1.

Question 37.
A train standing at the outer signal of a railway station blows a whistle of frequency 400 Hz still air,
(i) What is the frequency of whistle for a platform observer when the train.
(a) approaches the platform with speed of 10 ms^-1.
(b) recedes from the platform with speed of 10 ms^-1.
(ii) What is the speed of sound in each case? The speed of sound in still air 340 ms^-1.

Dharwad District
First PUC Annual Examination, March 2018

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer All questions: ( 10 × 1 = 10 )

Question 1.
Define absolute error.

Question 2.
What is position vector?

Question 3.
The force ‘F’ acting on a body displaces it through a distance ‘S’ perpendicular to its direction.
What is the work done by the force?

Question 4.
Write the relation connecting angular velocity and linear velocity.

Question 5.
State Hooke’s law.

Question 6.
Mention SI unit of pressure.

Question 7.
When the flow of the fluid is said to be steady flow?

Question 8.
Name the instrument used to measure temperature of the substance.

Question 9.
State zeroth law of thermodynamics.

Question 10.
Define mean free path.

Part – B

III. Answer any Five of the following questions: ( 5 × 2 = 10 )

Question 11.
Name any two fundamental forces in nature.

Question 12.
Mention any two applications of dimensional analysis.

Question 13.
Write any two differences between distance and displacement of a particle.

Question 14.
What is vector quantity? Give an example for it.

Question 15.
How linear momentum of a body vary with its mass and velocity?

Question 16.
Write two conditions for equilibrium of a rigid body.

Question 17.
State Pascal’s law. Name any one device which works on Pascal’s law.

Question 18.
Mention Newton’s formula for speed of sound in gases and explain the terms used.

Part – C

III. Answer any Five of the following questions: ( 5 × 3 = 15 )

Question 19.
Define centripetal acceleration. Mention an expression for centripetal acceleration and explain the symbols used.

Question 20.
Write any three advantages of friction.

Question 21.
Show that instantaneous power is equal to scalar product of force and velocity.

Question 22.
Obtain the relation connecting angular momentum and torque for a particle.

Question 23.
Derive an expression for acceleration due to gravity in terms of mass and radius of the earth.

Question 24.
Write any three applications of elastic behaviour of materials.

Question 25.
Mention any three factors on which amount of heat added to increase the temperature of the substance depends.

Question 26.
What is an ideal gas? Write ideal gas equation. At what condition real gases behaves as ideal gas?

Part – D

IV. Answer any Two of the following questions: ( 2 × 5 = 10 )

Question 27.
What is velocity – time graph? Derive V² = V₀²+ 2ax with usual notations using velocity – time graph.

Question 28.
Derive an expression for maximum safe speed of a car moving on banked circular road.

Question 29.
What is meant by moment of inertia? State and explain (a) Theorem of perpendicular axes and (b) theorem of parallel axes.

V. Answer any Two of the following questions: ( 2 × 5 = 10 )

Question 30.
Explain the working of Carnot engine with necessary P-V diagram.

Question 31.
Obtain an expression for period of oscillations of a load attached to a spring.

Question 32.
Derive an expression for fundamental frequency of oscillation of a stretched string.

VI. Answer any Three of the following questions: ( 3 × 5 = 15 )

Question 33.
A cricket ball is thrown at a speed 25 ms^-1 in the direction 30° above the horizontal. Calculate:
(a) The maximum height reached by the ball and
(b) The time taken by the ball to reach the initial height. (Given: Acceleration due to gravity g = 9.8 ms^-2 )

Question 34.
A overhead tank of volume 50m³ is to be filled with water in 30 minutes. If the tank is at a height of 6m, what is the power of the pump to be used?
(Given: density of water = 1000 Kg m^-3, Acceleration due to gravity g = 9.8 ms^-2)

Question 35.
Calculate the orbital velocity and period of revolution of an artificial satellite of earth revolving at a height of 200 km from earth’s surface. (Given: Radius of the earth = 6400 km, Mass of the earth = 6 × 10²⁴ Kg and Gravitational constant G = 6.7 × 10¹¹ Nm² kg^-2)

Question 36.
A cylindrical copper rod of diameter 0.04 m and length of 0.5 m is heated at one end by steam. The other end is kept at 0°C. Find the quantity of heat conducted across any section per minute. (Given: thermal conductivity of copper s 385 W m^-1 K^-1).

Question 37.
A train moving at a speed of 20 ms^-1 towards a station sounding a whistle of frequency 500 Hz. Calculate the apparent frequencies of the whistle as heard by the man standing on the platform when the train
(a) Approaches him
(b) Recedes from him
(Velocity of sound in air is 330 ms^-1)

Bangalore South District
First PUC Annual Examination, March 2018

General Instructions:

1. All parts are compulsory.
2. Answers without relevant diagram / figure / circuit wherever necessary will not carry any marks.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer All questions: ( 10 × 1 = 10 )

Question 1.
What is the basis of cesium atomic clock?

Question 2.
Which component of velocity is constant in a Projectile motion?

Question 3.
Define inertia.

Question 4.
State work – Energy theorem.

Question 5.
Mention the relation between Torque and angular momentum of a particle.

Question 6.
What are Elastomers?

Question 7.
State Bernoulli’s principle.

Question 8.
How does viscosity of a liquid changes with rise in temperature?

Question 9.
Mention the significance of zeroth law of thermodynamics.

Question 10.
How does an average Kinetic Energy of gas Molecules depend on the absolute temperature?

Part – B

II. Answer any Five of the following questions: ( 5 × 2 = 10 )

Question 11.
Write any two fundamental forces in nature.

Question 12.
Mention any two sources of systematic errors. .

Question 13.
Distinguish between path length and displacement.

Question 14.
Define the terms (i) Null vector or Zero vector (ii) Unit vector

Question 15.
Classify the nature of flow of liquid on the basis of Reynolds number.

Question 16.
Give Kelvin-plank statement and claussius statement.

Question 17.
What are free oscillations and forced oscillations?

Question 18.
What are longitudinal waves and transverse waves?

Part – C

III. Answer any Five of the following questions: ( 5 × 3 = 15 )

Question 19.
Obtain an Expression for time of flight of a projectile.

Question 20.
What is Friction? Write any two advantages of friction.

Question 21.
What is collision? Distinguish between Elastic collision and Inelastic collision.

Question 22.
State Kepler’s law of planetary motion.

Question 23.
Draw a typical Stress-Strain curve for a metal. Mention yield point and Fracture point.

Question 24.
Show that volume coefficient of thermal expansion α_v = \(\frac{1}{T}\) for ideal gas at constant pressure.

Question 25.
Mention any three assumptions of kinetic theory of gases.

Question 26.
Discuss modes of vibration of air column in a closed pipe.

Part – D

IV. Answer any Two of the following questions: ( 2 × 5 = 10 )

Question 27.
What is Uniform Circular Motion? Obtain an expression for centripetal acceleration.

Question 28.
Obtain an expression for maximum safe speed of a vehicle on a banked road in circular motion.

Question 29.
State and explain parallel axes theorem and perpendicular axes theorem.

V. Answer any Two of the following questions: ( 2 × 5 = 10 )

Question 30.
Obtain an expression for total energy of a satellite revolving in circular orbit around a planet.

Question 31.
Explain different stages of Carnot’s cycle with P-V- diagram.

Question 32.
Derive an expression for time period of oscillating bob of simple pendulum.

VI. Answer any Three of the following questions: ( 3 × 5 = 15 )

Question 33.
From a balloon ascending with a velocity of 9.8 ms^-1, a stone was dropped and it reached the ground in 1 Is. How high was the balloon? When the stone was dropped and with what velocity did it hit the ground. (g = 9.8 ms^-2)

Question 34.
A pump on the ground floor of a building can pump up water to fill a tank of volume 30m³ in 15 minutes. If the
tank is 40m above the ground and efficiency of the pump is 30%. How much power is consumed by the pump? (Density of water 103 kgm^-3, g = 9.8 ms^-2).

Question 35.
A dental drill accelerates from rest to 900 rpm in 2 sec. What is the angular acceleration? How many revolutions does it make in coming to full speed?

Question 36.
Find the time for which a layer of ice 5 cm thick on the surface of a pond will increase its thickness by 0.1 cm when temperature of the surrounding air is – 20°C.
Thermal conductivity of ice = 2.1 Wm^-1 K^-1 density of ice = 900 Kg m-3
Latent heat of ice = 3.36 × 10⁵ J Kg^-1

Question 37.
Two cars are approaching each other on a straight road and moving with a velocity 60 Kmph. If the sound produced in one car is of frequency 500 Hz. What will be the frequency of sound as heard by a person sitting in another car? When the car has crossed and moving away from each other, what will be the frequency of sound as heard by the same person, (speed of sound in air is 332 ms^-1).

Students can Download 1st PUC Chemistry Previous Year Question Paper March 2013 (North), Karnataka 1st PUC Chemistry Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

1st PUC Chemistry Previous Year Question Paper March 2013 (North)

Time: 3.15 Hours
Max Marks: 90

Instructions:

1. Write the question number legibly in the margin.
2. Answer for a question should be continuous.

Part – A

I. Answer the EIGHT of the following : ( 8 × 1 = 8 )

Question 1.
Write the IUPAC name of

Answer:
3, 4- dimethyl hexane.

Question 2.
Draw the staggered conformation of ethane.
Answer:

Question 3.
State modern periodic law.
Answer:
Properties of elements are periodic functions of their atomic numbers.

Question 4.
What is meant by octet rule?
Answer:
It is the tendency of atom to attain 8 electrons in valence shell.

Question 5.
Name the process in which hydrogen is obtained as a by product?
Answer:
Electrolysis of brine solution.

Question 6.
Which alkali metal is the strongest reducing agent?
Answer:
Lithium or Li.

Question 7.
How many significant figures in 6.022 × 10²³?
Answer:
4 or Four.

Question 8.
Which orbital is specified by l = 2 and n = 3?
Answer:
3d.

Question 9.
State Boyle’s law.
Answer:
At constant temperature the volume of a given mass of a gas is inversely proportional to the pressure.

Question 10.
Write relationship between ∆H and ∆U?
Answer:
∆H = ∆U + RT∆n.

Question 11.
What is effect of catalyst on the equilibrium of a reversible reaction.
Answer:
A catalyst has no effect on the position of equilibrium but it helps the reaction to attain equilibrium quickly.

Part – B

II. Answer any EIGHT of the following questions. ( 8 × 2 = 16 )

Question 12.
Define functional group.
Answer:
Atom or group of atom which determine the characteristic properties of organic compound.

Question 13.
State Markownikoff’s rule.
Answer:
When an asymmetric reagent adds up to an unsymmetrical alkene, the negative part of the adding molecule goes to the carbon atom with lesser number of hydrogen atoms while the positive part to the other carbon atom.

Question 14.
What is electron gain enthalpy?
Answer:
The enthalpy change occurs when an electron is added to isolated gaseous atom to convert into anion.

Question 15.
Write electronic configuration of C₂ molecule ? What is its magnetic property?
Answer:
\(\sigma_{1 \mathrm{s}^{2}} \sigma_{1 \mathrm{s}^{2}}^{*} \sigma_{2 \mathrm{s}^{2}} \sigma_{2 \mathrm{s}^{2}}^{*}\left(\pi 2 \mathrm{p}_{x}^{2}\right)\left(\pi 2 \mathrm{p}_{y}^{2}\right)\) Diamagnetic.

Question 16.
What is diagonal relationship? Give an example.
Answer:
Lithium shows similarities to magnesium and beryllium to aluminium in many of their properties. This type of diagonal similarity is commonly referred to as diagonal relationship in periodic table.

Question 17.
Diamond is a bad conductor of electricity but graphite is a good conductor. Justify the statement.
Answer:
Due to sp³ hybridisation in diamond, no free electrons are present.
In graphite due to sp² hybridisation there are free electrons to conduct electricity.

Question 18.
What mass of calcium carbonate is to be decomposed to obtain 4.4 g of CO₂ in the following reaction.

(molecular mass of CaCO₃ = 100g) .
Answer:

Question 19.
State and illustrate Pauli’s exclusion principle.
Answer:
No two electrons in an atom can have all same set of four quantum numbers alike.

Question 20.
Write Vander Waals equation for one mole of a gas and name any two terms.
Answer:
\(\left(p+\frac{a}{V^{2}}\right)(V-b)=R T\)
P = pressure, V = volume, R = universal gas constant, T = absolute temperature

Question 21.
What type of system, the following systems are
i) a cup containing hot tea
ii) hot coffee placed in a thermos flask?
Answer:
i) open system
ii) isolated system.

Question 22.
State Le Chatelier’s principle.
Answer:
If a system under equilibrium be subjected to a change in temperature, pressure or concentratio, then the equilibrium shifts itself in such a way so as to neutralise the effect of the change.

Question 23.
Chemical equation is dynamic. Give reason.
Answer:
Both forward and backward reactions are occuring at the same rate.
The concentration of the reactants and products remains constant.

Part – C

III. Answer any FOUR of the following questions : ( 4 × 4 = 16 )

Question 24.
What is resonance effect? Name one group each showing + R and – R effect.
Answer:
The resonance effect is defined as the polarity produced in the molecule by the interaction of two π bonds or between a π -bond and lone pair of electrons present in conjugated molecular.
+R_effect : -NH₂, – NHCOCH₃, – CH₃
-R_effect : -NO₂, -CN, -CH0, -COOH

Question 25.
Define chain and functional isomerism. Give examples for each isomerism.
Answer:
Compounds having same molecular formula but differing in arrangement of atoms in chain is called isomerism.
Ex – Butane C₄H₁₀

Functional Isomerism
Compounds having same molecular formula but differing in functional group is called functional isomerism.
Ex :

Question 26.
(a) Explain the mechanism of nitration of benzene?
Answer:
Nitration benzene reacts with a mixture of concentrated nitric acid and concentrated sulphuric acid at 50°C to form nitrobenzene.

Mechanism : This involves the following steps.
Step 1 : Generation of electrophile nitronium ion NO
HNO₃ + 2H₂SO₄ → NO₂⁺+ H₃O⁺ + 2HSO₄^–

Step 2 : The electrophile NO₂⁺ attacks the benzene ring to form a carbocation which is resonance stabilized.

Step 3 : Loss of a proton to give nitrobenzene. The proton is removed by HSO₄^–

(b) Mention the catalyst used in Friedel Crafts reaction.
Answer:
anhydrous AlCl₃.

Question 27.
(a) Explain the mechanism of chlorination of methane.
Answer:
Mechanism of chlorination of methane involves three types.
Step 1 : Initiation : Chlorine absorbs energy and undergoes homolysis to give chlorine free radicals.

Step 2 : Propagation : Chlorine free radical reacts with methane to give methyl free radical.
Cl^•+ CH₄ → CH₃^•+HCl

The methyl free radical reacts with chlorine to form methyl chloride and chlorine free radical.
CH₃^•+ Cl₂ → CH₃Cl + Cl^•

Step 3 : Termination : Free radiais combine to form stable products.
Cl^• + Cl^• → Cl (Chlorine)
CH₃^•+CH₃^•→ C₂H₆ (Ethane)
CH₃^•+ Cl^• → CH₃Cl (Methyl Chloride)

(b) Draw the structure of trans 1, 2- dibromo ethene.
Answer:

Question 28.
(a) Define geometrical isomerism. Give an example.
Answer:

restricted or hindered rotation about C = C bond is called geometrical isomerism.

(b) Name the product when calcium carbonte is treated with water.
Answer:
Acetylene.

Question 29.
What is pollutant? Mention the three gaseous air pollutants.
Answer:
Chemicals which bring about undesirable changes in the environment are called pollutants.
Ex : Nitric oxide (NO), Nitrogen dioxide (NO₂), sulphur dioxide (SO₂)

Part – D

Answer any FIVE of the following questions : ( 5 × 5 = 25 )

Question 30.
(a) Define ionisation enthalphy. How does it vary along the period and down the group in the periodic table.
Answer:
The minimum amount of energy which is needed to remove the most loosely bounded electron from a neutral isolated gaseous atom in its ground state to form a cation also in a gaseous state.

The ionisation enthalpy decreases down the group because the atomic size increases down the group and effective nuclear charge decreases. Hence removal of electrons become easier.

Ionisation energy increases along the period because the atomic size decreases from left to right in a period. Hence effective nuclear charge increases and removal of electrons becomes more and more difficult.

(b) How many periods are there in the periodic table?
Answer:
7 – periods.

Question 31.
(a) Draw the energy level diagram of O₂ molecule and calculate the bond order, why O₂ is paramagnetic?
Answer:

Energy level diagram of oxygen molecule
Bond order = \(\frac{N_{b}-N_{a}}{2}=\frac{8-4}{2}=\frac{4}{2}=2\)

(b) Give two differences between bonding and antibonding molecular orbitals.
Answer:

Bonding molecular orbitals	Anti-bonding molecular orbitals
1. Formed by the addition wave functions atomic orbitals.	1. Formed by the subtraction of wave functions atomic orbitals.
2. Have less energy than the atomic orbitals which combined	2. Have more energy than the atomic orbitals which combined.

Question 32.
(a) What is hydrogen bond? Give an example each for inter and intra molecular hydrogen bond.
Answer:
A hydrogen bond is the attractive force which binds hydrogen atom of one molecule with electronegative atom CF₁ O or N present in another molecule.
Intermolecular hydrogen bond – Ex -HF
Intramolecular hydrogen bond – Ex – O – nitrophenol.

(b) According to VSEPR theory, predict the shape of H₂O and NH₃ molecules.
Answer:
H₂O – bent V shaped.
NH₃ – pyramidal.

Question 33.
(a) Balance the following redox reaction using oxidation number method.
Cr₂O₇^-2+ S^2- + H⁺ → Cr³⁺ + S + H₂O.
Answer:

Multiply oxidation equation by the extent of reduction & reduction equation by the extent of oxidation.
Eqn (1) × 6; 6S^2- → 6S
Eqn (2) × 2; 2Cr₂O₇² → 4Cr³⁺
Add both the equations
2CrO-+ 6S^2- → 4Cr³⁺ + 6S
Balance oxygen
2CrO ^2-+ 6S^2- → 4Cr³⁺+ 6S + 14 H₂O
Balance hydrogen
2Cr₂O₇^2-+ 6S^2- + 28H⁺ → 4Cr³⁺+ 6S + 14 H₂O

(b) Identify the type of redox reactions.
i) Zn (s) + CuSO₄ (aq) → ZnSO₄ (aq) + Cu(s).
ii)
Answer:
i) Displacement type
ii) Decomposition type

Question 34.
(a) What happens when metal Mg is treated with dilute hydrochloric acid and write the equation.
Answer:
Mg + 2HCl → MgCl₂ + H₂ ↑
When Mg is treated with HCl, MgCl₂ and H displaces hydrogen gas.

(b) Why are metallic hydrides also called interstitial hydrides.
Answer:
In these hydrides, hydrogen occupies interstices in the metal lattice producing distortion without any change in its type so they are also called interstitial hydrides.

(c) Give two uses of hydrogen.
Answer:

1. Dihydrogen is used in the manufacture of vanaspathi fat by the hydrogenation of polyunsaturated vegetable oil.
2. Widely used in the manufacture of metal hydrides.

Question 35.
(a) Name the raw materials used in manufacture of Na₂CO₃ by Solvay process.
Answer:
Ammonia, CO₂, sodium chloride, ammonium hydrogen carbonate.

(b) Mention biological role of Na and Ca ions.
Answer:
Na – are involved in transmission of nerve signals.
Ca – 99% of body calcium is present in bones and teeth.

(c) Which alkali metal gives golden yellow colour to the flame?
Answer:
Sodium.

Question 36.
(a) Define catenation and name the element showing maximum property of catenation.
Answer:
Self linking of carbon atom to form a long /branched chain/cyclic ring is called catenation.
Carbon has maximum catenation property.

(b) What is the repeating unit in Organo Silicon polymer? Name the starting material used in the manufacture of Organo Silicon Polymer.
Answer:
(-R₂SiO-) is the repeating unit.
Methyl chloride and silicon in presence of copper as catalyst at temperature 573 K are the starting material.

OR (Internal Choice)

Question 36.
(a) Name the compound of group – 13 element which exist as dimer and draw the structure of the compound.
Answer:
AlCl₃ Structure

(b) What is inert pair effect? Illustrate it with suitable example.
Answer:
The occurrence of oxidation states two unit less than that of group oxidation states are attributed as inert pair effect.
Ex : Ge, Sn and Pb prefer to exhibit + 2 state because of inert pair effect i.e. ns² electrons remain inert and do not involve in bonding.

Part – E

Answer any FIVE of the following questions :  ( 5 × 5 = 25 )

Question 37.
(a) carbohydrate containing 40% carbon, 6.73% hydrogen and 53.3% oxygen. The molecular mass of compound is 180. Determine its molecular formula.
Answer:

∴ Empirical formula = CH₂O.
Molecular mass of compound =180
Empirical mass = CH₂O. = 12 + 2 × 1.008 + 16 = 30
\(\mathrm{n}=\frac{\mathrm{M} \cdot \mathrm{M}}{\mathrm{E} \cdot \mathrm{M}}=\frac{180}{30}=6\)
Molecular formula = C₆H₁₂O₆ = Glucose

(b) Define empirical formula.
Answer:
It is the simplest formula of compound which gives the relative number of atoms of different elements present in a molecule of a compound.

Question 38.
(a) Calculate the wavelength of spectral line when an electron in hydrogen atom undergoes transition from 3rd energy level to 2nd energy level (R = 109678 cm^-1).
Answer:
\(\frac{1}{\lambda}\) = R \(\left[\frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}}\right]\) = 109678 cm^-1 \(\left[\frac{1}{2^{2}}-\frac{1}{3^{2}}\right]\)
\(\frac{1}{\lambda}\) = 15245.242 cm^-1
l = \(\frac{1}{15245.242 \mathrm{cm}^{-1}}\) = 0.00006559 cm = 6.559 × 1O^-5 cm.

(b) Mention the shape of d-orbitals.
Answer:
double dumbell shaped.

Question 39.
(a) Write four postulates of kinetic theory of gases.
Answer:

1. All gases are made up of a large number of very small particles called molecules.
2. The gas molecules move randomly in all possible directions in straight lines. The direction of motion changes when they collide with other molecules.
3. The molecules are so small that their individual values is negligible as compared to the total volume of gas.
4. There is no force of attraction or repulsion between the molecules of a gas.

(b) What is the value of gas constant.
Answer:
R = 8.314 JK^-1 mol^-1.

Question 40.
(a) Calculate the enthalpy of formation of liquid benzene (C₆H₆) given the enthalpies of combustion of carbon, hydrogen and benzene as -393.5 KJ, -285.83 KJ and -3267.0 KJ respectively.
Answer:
Required equation
6C(s) + 3H₂(g) → C₆H₆ (l) Δ_fH = ?
Given Data : C(s) + O₂(g) → CO₂(g)  Δ_cH = -393.5KJ
H₂(g) + \(\frac{1}{2}\) O₂(g) → H₂O(l)  ∆_cH = -285.83K
C₆H₆(l) + \(\frac{15}{2}\) O₂(g) → 6CO₂ + 3H₂O  Δ_cH = -3267. 0KJ

(b) What is aspontaneous process?
Answer:
A spontaneous process is one which occurs by itself without any external aid.

OR (Internal choice)

(a) Calculate the enthalpy of combustion of methanol (CH₃OH) given enthalpies of formation of CH₃OH ₍₁₎ CO_2(g) and H₂O₍₁₎ as -239 KJ, -393.5 KJ and -286 KJ respectively.
Answer:
Required Eqn. CH₃OH(l) + \(\frac{3}{2}\)O₂(g) → f CO₂(g) + 2H₂O(l)  ∆_cH = -?
Given data
(1) C(s) + 2H₂(g) + \(\frac{1}{2}\) O₂(g) → CH₃OH(l)  ∆_fH = = -239 kJ
(2) C(s) + O₂(g) → CO₂(g)   ∆_fH = -393.5 Id
(3) H₂(g) + \(\frac{1}{2}\)O(g) → H₂O(l)  ∆_fH = -286 kJ
Reverse eqn( 1) and multiply 3 by 2 and add all three

(b) What happens to the entropy, when liquid is converted into vapours?
Answer:
Entropy increases.

Question 41.
(a) Calculate K. for the following equilibrium 2SO₂(g) + O₂(g) ⇌ 2SO₃(g). Given equilibrium constant of SO₂,O₂ and SO₃ are 0.3 M, 0.41 M, and 1.45 M respectively. What happens to the above equilibirum if (i) SO₂ is added (ii) O₂ is removed.
Answer:
\(K_{c}=\frac{\left[\mathrm{SO}_{3}\right]^{2}}{\left[\mathrm{SO}_{2}\right]^{2}\left[\mathrm{O}_{2}\right]}\)
= \(\frac{(1.45)^{2}}{(0.3)^{2}(0.41)}\) = 56.97
i) Addition of SO₂ favours forward reaction.
ii) Removal of O₂ favours backward reaction.

(b) Identify the two conjugate acid base pairs in the following NH₃ + HCl ⇌ NH₄⁺+ Cl^–
Answer:
NH₃ / NH₄⁺ , HCl / Cl^–

Question 42.
(a) What is common ion effect? Give an example.
Answer:
Suspension of degree of dissociation of weak electrolyte by the addition of strong electrolyte having a common ion is called common ion effect.

(b) Calculate the solubility of lead chloride (PbCl₂) at 298K, if its solubility product is 1.6 × 10^-5.
Answer:
\(S=\sqrt{\frac{K_{s p}}{4}}=\sqrt{\frac{1.6 \times 10^{-5}}{4}}=1.58 \times 10^{-2} \mathrm{mol} / \mathrm{dm}^{3}\)

Question 43.
(a) State postulates of Bohr’s theory.
Answer:

1. Electrons revolve around the nucleus in an circular path of fixed radius and energy. These paths are called orbits.
2. The energy of an electron in the orbit does not change with time.
3. The frequency of radiation absorbed or emitted when transition occurs between two stationary states that differ in energy by ∆E.
   \(\gamma=\frac{\Delta \mathrm{E}}{\mathrm{h}}=\frac{\mathrm{E}_{2}-\mathrm{E}_{1}}{\mathrm{h}}\)
4. The angular momentum of an electron in a given stationary state can be expressed as
   mvr = n. \(\frac{h}{2 \pi}\) n = 1, 2, 3……

(b) Write de Broglies equation.
Answer:
λ = \(\frac{\mathrm{h}}{\mathrm{mv}}\) or \(\frac{\mathrm{h}}{\mathrm{mc}}\)

Question 44.
(a) Define the terms molarity and mole fraction.
Answer:
Molarity (M) = \(\frac{\text { No. of moles of solute }}{\text { Volume of solution in litres }}\)
Mole fraction of A = \(\frac{\text { No. of moles of } \mathrm{A}}{\text { No. of moles of solution }}\)
= \(\frac{\mathbf{n}_{A}}{n_{A}+n_{B}}\)

(b) What is limiting reagent.
Answer:
The reactant which gets consumed, limits the amount of product formed is called limiting reagent.

Students can Download 1st PUC Chemistry Previous Year Question Paper March 2013 (South), Karnataka 1st PUC Chemistry Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

1st PUC Chemistry Previous Year Question Paper March 2013 (South)

Time: 3.15 Hours
Max Marks: 90

Instructions:

1. Write the question number legibly in the margin.
2. Answer for a question should be continuous.

Part – A

I. Answer the EIGHT of the following: ( 8 × 1 = 8 )

Question 1.
What is functional group?
Answer:
Properties of certain organic compounds determined by the presence of an atom or group of atom is called functional group.

Question 2.
Give one example which has K_c = K_p
Answer:
H₂(g) + I₂(g) ⇌ 2NO(s)
or
N₂ + O₂ ⇌ 2NO(g).

Question 3.
State modern periodic law.
Answer:
Properties of elements are the periodic function of their atomic number.

Question 4.
Give any one example for solid and vapour equilibrium.
Answer:
I₂ (solid) ⇌ I₂ (vapour)
OR
camphor (s) ⇌ camphor (vapour)

Question 5.
What is oxidation number of oxygen in hydrogen peroxide?
Answer:
Oxygen in H₂O₂ = -1

Question 6.
Mention one use of hydrogen.
Answer:
It is used as rocket fuel in space research.

Question 7.
What is Avogadro’s number?
Answer:
Avogadro’s number = 6.022 × 10²³

Question 8.
A wavelength of 100 nm of a radiation lies in which region?
Answer:
100 nm = UV

Question 9.
State Boyle’s law.
Answer:
At constant temperature the volume of given mass of a gas is inversely proportional to pressure.

Question 10.
Whether internal energy is extensive property or intensive property?
Answer:
Extensive property.

Question 11.
Write electronic configuration of alkali metals.
Answer:
[Nobel gas] ns¹.

Part – B

II. Answer any EIGHT of the following questions. ( 8 × 2 = 16 )

Question 12.
Calculate percentage composition of carbon and hydrogen in ethanol.
Answer:
Molecular mass of ethanol = 46.06
% carbon = \(\frac{24}{46}\) x 100 = 52
% of hydrogen = \(\frac{6}{46}\) x 100 = 13

Question 13.
Explain hydrogen bonding.
Answer:
Hydrogen bonding is defined as “Attractive force which binds hydrogen atom of one molecule with electronegative atom (F, O, or N) of another molecule.

Question 14.
Define Hund’s rule of maximum multiplicity.
Answer:
Hund’s rule: “Pairing of electron in the orbitals having same subshell doesn’t take place until each orbital has one electron each”.

Question 15.
Represent the behaviour of real gases from ideal gases graphically.
Answer:

Question 16.
Represent the chemical equation when butane (Cooking gas – LPG) burnt completely in air?
Answer:
C₄H₁₀(g) + \(\frac{13}{2}\) O₂ (g) → 4CO₂ (g) + 5H₂O(g)   ∆_cH = -2658.0 KJ

Question 17.
Explain lewis acid and base concept.
Answer:
Acid → Accept a pair of electron
Base → Donate a pair of electron

Question 18.
Define ionisation enthalphy with an example.
Answer:
Ionisation enthalpy “The amount of energy to remove outermost electron from an isolated gaseous atom”.
eg. Na – 498. 5 KJ/mol.

Question 19.
What is redox reaction? Give one example.
Answer:
A chemical reaction in which both oxidation and reduction processes occur simultaneously are known as redox reaction.
eg. 2Na(s) + Cl₂ (g) → 2NaCl(s)

Question 20.
Give any two uses of heavy water.
Answer:

1. It is used as a mild bleaching agent.
2. Used an an antiseptic in surgery.

Question 21.
At equilibrium the concentration of N₂ = 3.0 × 10^-3 M, O₂ = 4.2 × 10^-3 M and NO = 2.8 × 10^-3 M in a sealed tube. What will be K_c for the reaction N₂(g)+ O₂(g) ⇌ 2NO(g)?
Answer:
K_c = \(\frac{\left[\mathrm{NO}_{2}\right]^{2}}{\left[\mathrm{O}_{2}\right]\left[\mathrm{N}_{2}\right]}\)
= \(\frac{2.8 \times 10^{-3}}{10^{-3} \times(3.0)(4.2) \times 10^{-3}}\)
= 0.622

Question 22.
What is resonance effect?
Answer:
The permanent polarity is produced by the interaction of lone pair and n electrons in conjugate system.

Question 23.
In sulphur estimation 0.157 g of organic compound gave 0.4813 g of barium sulphate calculate the percentage of sulphur in the compound.
Answer:
Mol. mass of BaSO₄ = 233
233 g of BaSO₄ contain 32 g of sulphur
0.483 g of BaSO₄ contain =
% Sulphur = \(\frac{32 \times 0.483 \times 100}{233 \times 0.157}\) = 42.10%

Part – C

III. Answer any FOUR of the following questions : ( 4 × 4 = 16 )

Question 24.
(a) What is chromatography?
Answer:
Chromatography: It is important technique which separates mixtures into their compounds and also tests the purity of compounds.

(b) Explain how is an organic compound separated by distillation method?
Answer:
Distillation is method used to separate constituents of a liquid mixture which differ in their boiling points. Distillation is a process which involves two steps.

1. Vapourisation: Liquid is converted into vapours.
2. Condensation: Vapours are condensed again into liquid.

Question 25.
(a) Explain in brief how is nitrogen detected using sodium fusion extract?
Answer:

Experiment	Observation	Inference
Organic compound + sodium fusion extract + boiled with FeSO4 + conc. H2SO4	Blue colour	Compound is Nitrogen

(b) Write the structure of 1,2 – Dibromobenzene.
Answer:

Question 26.
(a) Explain mechanism of chlorination of methane.
Answer:
The mechanism involves three steps:
(1) Initiation : A chlorine molecule absorbs energy from sunlight to form free radicals.

(2) Propagation : A chlorine free radical reacts with methane forming a HCl and methyl free radical.
CH₄ + Cl^• → CH₃^•+ HCl
(b) The methyl free radical attack chlorine molecule forming a methyl chloride and chlorine free radical
CH₃^•+ Cl₂ → CH₃Cl + Cl
Termination : The two free radical combines to form product.
Cl^• + Cl^• → Cl (Chlorine)
CH₃^•+CH₃^•→ C₂H₆ (Ethane)
CH₃^•+ Cl^• → CH₃Cl (Methyl Chloride)

(b) Give one use of ethene.
Answer:
Ethene is used for artificial ripening of fruits.

Question 27.
(a) How is ethyne prepared from calcium carbide?
Answer:
When calcium carbide react with water to form ethyne.
CaC₂ + 2H₂O → CH ≡ CH +Ca(OH)₂

(b) Mention the formula of Huckle rule.
Answer:
Huckel formula = (4n + 2) π electron

Question 28.
(a) Explain mechanism of nitration of benzene.
Answer:

Mechanism: Step 1: Generation of electrophile
OH – NO₂ + H – HSO₄ → NO₂⁺+ HSO₄^–+ H₂O
Step 2 : Attack of electrophile on benzene ring to form carbocation.

Step 3 : The carbocation loses proton to form nitrobenzene

(b) Which element is detected by kjeldhal method?
Answer:
Nitrogen

Question 29.
(a) What is ozone hole? Explain.
Answer:
One of the reason of ozone hole by a class of compounds called freons. Due to several kinds of human activities involving freons they will diffuse into ozone layer of the stratosphere.
They undergo photodissociation as follows:

The chlorine free radical react with ozone to form chlorine monoxide radical and O₂
O₃ + Cl^• → ClO^• + O₂
Reaction of chlorine monoxide radicals with oxygen generates chlorine radicals
ClO^• + O → O₂ + Cl^•
The chlorine radicals are continuously regenerated causes damage of ozone layer. This is a ozone hole.

(b) Explain green house effect.
Answer:
The heating of atmosphere due to absorption of IR radiation emitted by earth by the gases of atmosphere is called greenhouse effect.

Green house gases absorb large amount of energy from sunlight and transfer it as heat by which earth gets heated. But they do not readily radiate back the earth’s heat energy to the space. Instead they reflect back a part of the heat energy to the lower atmosphere.

Part – D

Answer any FIVE of the following questions : ( 5 × 5 = 25 )

Question 30.
(a) Why size of cation is smaller than its parent atom?
Answer:
A cation is formed by the loss of electron which decrease in size due to more attraction by nucleus, because of increase in nuclear charge.

(b) Which of these isoelectronic species -Al³⁺ or Mg²⁺ has lower size?
Answer:
Higher charges lower the size.
Al³⁺ has lower size than Mg²⁺.

(c) How is a chemical bond formed?
Answer:
A bond is formed by the attraction force which holds various constituent together in different chemical species.

Question 31.
(a) Define bond length.
Answer:
The average distance between the centres of the nucleus of the two bonded atoms in a molecule.

(b) Explain sp³ hybridisation in methane.
Answer:
The electronic configuation of carbon in the excited state is 1s¹ 2s¹ 2P_x¹  2P_y¹ 2P_z¹. One 2s orbital and 3p orbitals hybridise to give four hybrid orbitals. The hybrid orbitals are directed towards the comer of a regular tetrahedron. The angle between any two orbitals is 109°28′. The four sp³ hybrid orbitals of carbon atom overlap axially with s-orbitals of four hydrogen atom to give C – H σ bonds.
The C – H σ bonds is sp³ – s bond. H – C – H bond angle is 109°28′. The shape of the molecule is tetrahedral.

Question 32.
(a) Write electronic configuration of lithium molecule.
Answer:
(σ₁1s)² (σ^x1s)² (σ2s)²

(b) Why Helium (He₂) molecule does not exist.
Answer:
Helium molecule has bond order equal to zero, hence molecule does not exist.

(c) Define bond order.
Answer:
It is the number of covalent bonds holding the atoms in the molecule.

Question 33.
(a) Give any three postulates of molecular orbital theory.
Answer:

1. The molecular orbitals are formed by the combination of atomic orbitals of comparable energies and proper symmetry.
2. The number of molecular orbitals formed is equal to the number of combining atomic orbitals.
3. The bonding molecular orbital has lower energy and hence greater stability than the corresponding antibonding molecular orbital.

(b) Differentiate between σ bond and π bond.
Answer:

Sigma bond	Pi bond
1. Sigma bond formed by the axial combination of orbitals.	1. Pi bond formed by the head to head combination.
2. More efficient	2. Less efficient

Question 34.
(a) Mention rules used to balance a chemical reaction by oxidation number method.
Answer:

1. Oxidation number of a mono atomic ion is same as the charge on it.
2. Oxidation number of metals are positive and those of non metals are negative.
3. In neutral compounds, the sum of oxidation number of all the atoms is equal to zero.
4. In case of polyatomic ion, the sum of the oxidation numbers of all the atoms of the ion is equal to charge on the ion.

(b) Give an example of covalent hydride.
Answer:
CH₄, NH₃, HF, H₂O

Question 35.
(a) How is temporary hardness of water removed?
Answer:

1. By boiling of water.
2. By Clark’s method : In this method lime is added to the hard water. It precipitates out CaCO₃ and Mg(OH)₂ which can be filtered off.
   Ca(HCO₃) + Ca(OH)₂ → 2CaCO₃ ↓ +2H₂O

(b) Give one biological importance of sodium and potassium ion.
Answer:
Biological importance of sodium.
1. Transmit nerve signals.

Biological importance of potassium.
1. Activates many enzymes.

(c) Name the radioactive element of alkali metals.
Answer:
Francium.

Question 36.
(a) Potassium is lighter than sodium? Why?
Answer:
Potassium has unusual increase of size (or) density of K = 0.86 g/cm³, density of Na = 0.97 g/cm³,
Hence potassium is lighter than sodium.

(b) Give any two uses of sodium carbonate.
Answer:

1. Water softening
2. Laundering and cleaning.

(c) What happens when a piece of aluminium is added to dilute hydrochloric acid.
Answer:
Aluminium dissolves in HCl to liberate hydrogen gas.
2Al + 6HCl → 2AlCl₃ + 3H₂ ↑

Question 37.
(a) How is borax prepared?
Answer:
Borax can also be obtained by neutralisation of boric acid with Na₂CO₃
4H₃BO₃ + Na₂CO₃ → Na₂B₄O₇ + 6H₂O + CO₂. ↑

(b) Write a short note on fullerene.
Answer:
Fullerens are made by heating the graphite in an electric arc in the presence of inert gases. Fullerens are cage like molecules. It contains twenty six membered rings and twelve five membered rings. All the C-atoms are equal, they will undergo sp² hybridisation. Each carbon atom form three sigma bonds with other three C-atoms. This ball shaped molecule has 60 vertices. It also contain both single and double bonds with C-C distances of 143.5 pm and 138.3 pm.

(c) Concentrated nitric acid can be transported in aluminium container. Give a reason.
Answer:
Conc. HNO₃ reacts with aluminium forms a protective layer called passive. It does not react further.

Part – E

Answer any FIVE of the following questions : ( 5 × 5 = 25 )

Question 38.
(a) Define Gay-Lussac’s law.
Answer:
At constant volume, the pressure of a fixed mass of a gas is directly proportional to its temperature.

(b) What is SI unit of luminous intensity?
Answer:
Unit – Candela or Cd.

(c) Define ‘mole’.
Answer:
Mole : It is the amount of substance that contain as many particles (atoms, ions, molecules) exactly 12 g of the C¹² isotopes.

Question 39.
(a) What is meant by average atomic mass?
Answer:
The susbtance which has isotopes, and found relative abundance.
eg 12C = 98.892
13C = 1.108
14C = 2 × 10^-10

(b) What is density? How is it calculated?
Answer:
Density of a substance is the amount of mass per unit volume.

(c) What are the fundamental particles of atom.
Answer:
Electron, proton and neutron.

Question 40.
(a) Mention the postulates of Bohr model of an atom?
Answer:

1. The electron in the hydrogen atom can move around the nucleus in a circular path of fixed radius and energy. These paths are called orbits.
2. The energy of an electron in the orbit does not change with time.
3. The frequency of radiation absorbed (or) emitted when transition ocurs between two stationary states that differ in energy by ΔE is given by
   
4. The angular momentum of an electron in a given stationary state can be expressed as mvr = \(\frac{\mathrm{nh}}{2 \pi}\)

(b). What is the vaiue of Rydberg’s constant.
Answer:
R = 2.18 x 1O^-18 J.

Question 41.
(a) Mention postulates of kinetic molecular theory of gases.
Answer:

1. All gases are made up of very large numbers of minute particles called molecules.
2. Intermolecular forces of attraction (or) repulsion are negligible.
3. The pressure exerted by a gas is due to the collisions made by the gas molecules on the walls of the container.
4. The average kinetic energy of the molecules is directly proportional to the absolute temperature.
5. The molecules are involved in rapid, random movement. During their motion, they collide with each other and also against the walls of the container.

OR (Internal choice)

(a) What is an ideal gas? Derive ideal gas equation?
Answer:
Ideal gas which obey’s Boyle’s law and Charle’s law at all temperatures or PV = RT
Derivation
\(\left(\mathrm{v} \propto \frac{1}{\mathrm{P}}\right) \mathrm{V} \propto \mathrm{T}\)
= V ∝ \(\frac{1}{\mathrm{P}}\) × P
= V = \(\frac{\mathrm{RT}}{\mathrm{P}}\) (R = gas constant)
PV = RT or
PV = nRT

(b) Explain surface tension.
Answer:
Surface tension = \(\frac{\text { Force }}{\text { Area }}\)
The molecules in liquid state on surface experience a net downward force and have more energy than the molecules in bulk, which don’t experience any net force.
If the surface of the liquid is increased by pulling a molecule from the bulk.

Question 42.
(a) State Charle’s law.
Answer:
Charles law : states that volume of a given mass of a gas is directly proportional to temperature at constant pressure.
V ∝ T at constant pressure.

(b) Write Van der Waal’s equation.
Answer:
Van der Waal’s equation
\(\left(P+\frac{a n^{2}}{V^{2}}\right)(V-n b)=n R T\)

(c) State first law of thermodynamics and write its mathematical statement.
Answer:
First law of thermodynamics “The energy of an isolated system is constant”.
∆U = q + w

Question 43.
(a) Calculate AG° for conversion of oxygen to ozone; \(\frac{3}{2}\) O₂(g) → O₂(g) at 298 K,
if K_p = 2.47 × 10^-29.
Answer:
ΔG° = -2.303RT log K_p
= -2.303 × 8.314 × 298 log 2.47 × 10^-29.
= 1.63 kJ/mole

(b) How is ΔU measured calorimetrically.
Answer:
The heat of combustion of a substance at constant volume is measured by calorimetric method.
The bomb is a closed container made of a heavy steel. The bomb is coated inside with gold to prevent oxidation of steel during combustion reaction. A known mass of the substance whose heat of combustion is to be determined is taken in the platinum cup. The bomb is filled with oxygen at a pressure of 20-25 atm. The bomb is closed with a tight screw cap.

The bomb is surrounded by water bath taken in a insulated outer vessel. The initial temperature of water bath is noted. Let it be t₁°C. The combustion is initiated by passing electric current through platinum filament. The heat evolved during combustion raises the temperature of water outside the bomb calorimeter. The highest temperature recorded by thermometer is noted. Let it be t₂°C.

Calculation

1. Let the mass of the substance taken be mg.
2. Let the molecular mass of the susbtance taken be ‘M’
3. Let the heat capacity of calorimeter be Q.
4. Let Δt be the rise in temperature.
5. Then Δu, the heat of combustion at constant volume.

Calculated by using the equation
\(\Delta \mathrm{U}=\mathrm{Q} \times \Delta \mathrm{t} \frac{\mathrm{M}}{\mathrm{m}} \mathrm{J}\)

Question 44.
(a) What is buffer solution?
Answer:
The property of certain solution which resist the change in pH on addition of small amount of acid (or) alkali to it. .

(b) State Lechatelier principle.
Answer:
If a system in equilibrium is subjected to a change of concentration, temperature (or) pressure, the equilibrium shifts in a direction so as to undo the effect of the change imposed.

(c) Derive P_H + P_OH = 14
Answer:
K_w = [H₃O⁺][OH^–] = 10^-14
Taking log of minus sign
-log K_w = – log(H₃O⁺) (OH^–)
-log K_w = – log[H₃O⁺] – log [OH^–]
PK_w = P_H + P_OH = 14
pH + pOH = 14

Question 45.
(a) Define ionic product of water.
Answer:
Ionic product of water may be defined as product of molar concentration of hydrogen ion and hydroxyl ion concentration at a given temperature
K_w = [H₃O⁺][OH^–] = 10^-14

(b) Derive an equation for dissociation constant of weak acid.
Answer:
Let us consider a weak acid HX dissociate in aqueous solution and attains equilibrium

where a is the extent of ionisation.
\(\mathrm{K}_{\mathrm{a}}=\frac{\left(\mathrm{H}_{3} \mathrm{O}^{+}\right)\left(\mathrm{X}^{-}\right)}{(\mathrm{HX})}=\frac{\mathrm{C} \alpha \cdot \mathrm{C} \alpha}{\mathrm{C}(1-\alpha)}\)
\(\mathrm{K}_{\mathrm{a}}=\frac{\mathrm{C} \alpha^{2}}{1-\alpha}\)
where Ka is called dissociation constant of acid.

Students can Download 1st PUC Physics Model Question Paper 2 with Answers, Karnataka 1st PUC Physics Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

Karnataka 1st PUC Physics Model Question Paper 2 with Answers

Time: 3.15 Hours
Max Marks: 70

General Instructions:

1. All parts are compulsory.
2. Draw relevant figure / diagram wherever necessary.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer the following questions : ( 10 × 1 = 10 )

Question 1.
Define velocity.
Answer:
The rate of change of differ cement is known as velocity.

Question 2.
What is a null vector?
Answer:
A vector whose magnitude is zero and that has any arbitrary direction is known as a null or zero vector.

Question 3.
W hat is the unit of measurement of energy used in our electricity bills?
Answer:
kWh

Question 4.
Where is the centre of mass of a meter stick?
Answer:
at 50 cm

Question 5.
Name the natural satellite of earth.
Answer:
Moon.

Question 6.
What is hydraulic stress?
Answer:
Hydraulic stress is the normal compressible force acting per unit area of the immersed body.

Question 7.
Why is the tip of the nib of a pen split?
Answer:
The tip of the nib of a pen is split in order to provide a capillary which helps the ink to rise to the end of the nib and enables it to write continuously.

Question 8.
Why some cooking pots have copper coating on the bottom?
Answer:
Copper is an excellent conductor of heat. The copper coating on the bottom of pots enables the cooking process quicker.

Question 9.
State the law of equipartition of energy.
Answer:
For gases in thermal equilibrium, the energy supplied to the gas is equally distributed among the degrees of freedom and molecules, so that energy per molecule per degree of freedom is \(\left(\frac{1}{2}\right)\) K_BT where k_B is Boltzmann’s constant.

Question 10.
Define amplitude of a wave.
Answer:
The maximum displacement of the wave is known as its amplitude.

Part – B

II. Answer any FIVE of the following questions: ( 5 × 2 = 10 )

Question 11.
Name a fundamental force which has long range.and a fundamental force which has short range of operation.
Answer:

• Short range – strong nuclear force.
• Long range – Gravitational force.

Question 12.
Distinguish between path length and displacement.
Answer:
Distance covered:

• It is the change in position of a particle without the mention of a direction.
• It is the actual length of the path covered by the particle.

Displacement:

• It is change in position of a particle in a specified direction.
• It is the shortest distance between the initial and the final point described by the particle.

Question 13.
The position of a particle is given by \(r=3.0 t \hat{i}+2.0 t^{2} \hat{j}+5.0 \hat{k}\) where t is in seconds and the coefficients have the proper units for r to be in metres. Find v(t) of the particle.
Answer:

Question 14.
What is impulse and impulsive force?
Answer:
A huge force acting on a body for a short interval of time is known as an impulsive force. Impulse is defined as the product of mass of the body and change in velocity of the body. Impulse = m(v – u).

Question 15.
State and explain Boyle’s law.
Answer:
At constant temperature, the volume of a given mass of a gas is inversely proportional to its pressure.
V ∝ \(\frac{1}{\mathrm{P}}\) at constant temperature
So that P₁V₁ = P₂V₂.

Question 16.
What is reversible process? Give an example.
Answer:
A process is reversible if it can be reversed such that both the system and the surrounding return to their original states.

Question 17.
A planet has same mass as that of earth, but its radius is half that of earth. If the acceleration due to gravity on earth is ‘g’, what is the acceleration due to gravity on that planet.
Answer:
Acceleration due to gravity on earth.
\(g_{E}=\frac{\mathrm{GM}}{\mathrm{R}^{2}}\)
If mass (M) of the planet is equal to the mass of the earth and radius (R) is half \(\left(\frac{\mathrm{R}}{2}\right)\) of the earth, the accleration due to gravity on that planet.

∴The acceleration due to gravity on that planet is twice the acceleration due to gravity on the earth.

Question 18.
Mention the expression for kinetic energy of a particle executing simple harmonic motion. Explain the terms.
Answer:
\(\mathrm{K.E}=\frac{1}{2} m \omega^{2} \mathrm{A}^{2} \sin ^{2}(\omega t+\phi)\)
\(\mathrm{K.E}=\frac{1}{2} \mathrm{k} \mathrm{A}^{2} \sin ^{2}(\omega t+\phi)\)
Where A → Amplitude
m → mass of the particles
W → angular frequency
t → time
k → force constant

Part – C

III. Answer any FIVE of the following questions : ( 5 × 3 = 15 )

Question 19.
Consider an equation v = v₀+ at, where v₀ is the initial velocity, v is the final velocity, a is the acceleration and t is the time taken. Check whether this equation is dimensionally correct.
Ans. v = v + at
[LT^-1 ] = [LT^-1 ] + [LT^-2 ][T¹ ]
(LT^-1) = [LT^-1] + [LT^-1]
Since energy term on the RHS has the same dimensional formula, hence the equation is dimensionally correct.

Question 20.
Derive an expression for centripetal acceleration.
Answer:
Let \(\vec{r}\) and \(\vec{r}^{\prime}\) be the position vectors and \(\vec{v}\) and \(\vec{v}^{\prime}\) veIocities of the object when it is at point P and P’. By definition, velocity at a point is along the tangent at that point in the direction of the motion. Since the path is circular \(\vec{v}\) is perpendicular to \(\vec{r}\) and \(\vec{v}^{\prime}\) is perpendicular to \(\vec{r}^{\prime}\).
Therefore, ∆\(\vec{v}\)is perpendicular to ∆\(\vec{r}\) Average acceleration \(\frac{\Delta \vec{v}}{\Delta t}\) is perpendicular to ∆\(\vec{r}\).
The magnitude of \(\vec{a}\) is, by definition, given by \(|\vec{a}|=\lim _{\Delta t \rightarrow 0} \frac{|\Delta \vec{v}|}{\Delta t}\)
The triangle formed by the position vectors is similary to the triangle formed by the velocity vectors.

lf ∆t is very small. ∆ will also small. The arc PP is approximately equal to \(|\Delta \vec{r}|\)
i.e., \(\lim _{\Delta t \rightarrow 0} \frac{|\Delta \vec{r}|}{\Delta t}\) = v. Thus, centripetal acceleration \(|\vec{a}|=\frac{v}{r} v=\frac{v^{2}}{r}\) and \(\vec{a}=\frac{v}{r} \frac{d \vec{r}}{d t}\).
The centripetal acceleration is always directed towards the centre. The centripetal force = ma.

Question 21.
Write any one disadvantage of friction. What are the different methods of reducing friction?
Answer:

1. Friction hinders motion of bodies.
2. Friction causes wear and tear of machinery parts.
3. Wear and tear can be minimised by polishing the surfaces and lubricating machinery parts with oil and grease etc.
4. Streamlining the bodies reduce fluid (air or water) resistance.

Question 22.
Differentiate between conservative force and non-conservative force with one example for each.
Answer:
The force is said to be conservative, if the work done by the force in moving a particle over a closed path is zero.
Eg: Electrostatic force .
The force is said to be non-conservative, if the work done by the force over a closed path is not zero.
Eg: viscous force is a liquid.

Question 23.
Find the force required to stretch a wire of area of cross section 2 x 10^-4 m² so that its length becomes 1.5 times original length. Young’s modulus = 3.6 x 10¹¹ Nm^-2.
Answer:
Y = \(\frac{\text { stress }}{\text { strain }}\)
A = 2 × 10^-4 m²
∆l = 1.51
Y = 3.6 × 10¹¹ Nm^-2
F= ?

Question 24.
State Pascal’s law. Give two applications of Pascal’s law.
Answer:
The total normal force exerted by a fluid on any surface in contact with it, is called fluid thrust. Devices which use the principles of pascal’s law are,

• Hydraulic brakes and
• Sphygmo manometer (used to measure blood pressure).

Question 25.
Determine the molar specific heat at constant volume for a mono atomic gas molecule.
Answer:
(dQ) = du = C_v dT
ie. C_v dT = \(\frac{f \mathrm{R} d \mathrm{T}}{2}\)
∴ C_v = \(\frac{f R}{2}\) for mono atonic gas, f = 3
C_v = \(\frac{3 \mathrm{R}}{2}\)

Question 26.
Give the theory of beats.
Answer:
Let y₁ = A sin ω₁t and y₂ = A sin ω₂t represent two progressive waves travelling in the same direction and superpose with each other.
y = y₁ + y₂ = A ( sin ω₁t + sin ω₂t )

and ω_b = ω₁ – ω₂ or f_b = f₁ – f₂ where f_b is known as the beat frequency and t_b = \(\frac{1}{f_{b}}=\frac{1}{f_{1}-f_{2}}\) as the beat period.

Part – D

IV. Answer any TWO of the following questions : ( 2 × 5 = 10 )

Question 27.
What is a projectile? Derive the equation of path of a projectile.
Answer:
A particle thrown into the space and whose motion is guided by the action of gravity is called as a projectile.
Let v be the velocity of projection. Let θ be the angle of projection. Let v_0x = v₀ cosθ and v_0y = v₀ sinθ represent X and Y components of velocities.
For the motion in (x, y) plane

We get y = ax – bx² which is quadratic equation representing equation of a parabola.
Hence trajectory of a projectile describes a parabola.

Question 28.
Illustrate the law of conservation of mechanical energy in case of a ball dropped from a cliff of height H.
Answer:
Energy can neither be created nor destroyed but can be transformed into other forms of energy.
Let a particle be at ‘C’. Initially the particle w ill be zero velocity. Let ‘h’ be the height of the particle.

P.E_c = mgh, K.E_c = 0
T.E = mgh
At B, K.E = \(1 / 2 \mathrm{mv}_{\mathrm{B}}=1 / 2 \mathrm{m}(2 \mathrm{g} x)=\mathrm{mg} x\)
P.E_B = mg (h – x)
Hence T.E = (mgh – mgx) + (mgx)
= mgh
At A, v_A²= 2gh
So that K.E = \(\frac{1}{2}\) m2gh = mgh
P.E_A = O.
Hence at all points A, B and C, the total energy is conserved.

Question 29.
Define moment of inertia of a body. State and explain perpendicular axis theorem and parallel axis theorem of moment of inertia.
Answer:
Statement : The moment of inertia about an axis perpendicular to two other axes acting in the same plane with their point of intersection being a point on it and the (third) axis passing through the common point, is equal to the sum of moments of inertia about the two axes.
e.g: I_z = I_x + I_y.
Let M be the mass of the disk of radius R.
M.I. about a point passing through the centre and perpendicular to the plane containing X and Y is I = \(\frac{M R^{2}}{2}\)
Since X and Y are in the same plane, I_x = I_y

∴ I_z = I_x + I_y becomes I_z = 2I_x
hence I_x = \(\frac{I_{Z}}{2}=\frac{M R^{2}}{4}\)
i.e. moment of inertia of a circular disc about the diameter \(\frac{I_{Z}}{2}=\frac{M R^{2}}{4}\)

V. Answer any TWO of the following questions : ( 2 × 5 = 10 )

Question 30.
Derive the expression for acceleration due to gravity at a point below the surface of earth. What is the value of acceleration due to gravity at the centre of the earth?
Answer:
Let ‘p’ be the mean density of the Earth. Let ‘R’ be the radius of the Earth.
Mass of the Earth M_E = Vρ
ME = \(=\frac{4}{3} \pi R_{E}^{3} \rho\)
Hence acceleration due to gravity,

Acceleration due to gravity at a depth ‘d’ due to radius R_Eand mass M_E, g(d) ∝ R_E


Note : For d = R_E (at the centre), \(\frac{\mathrm{d}}{\mathrm{R}_{\mathrm{E}}}\) = 1 and g(R_E) = 0.

Question 31.
What is thermal radiation? Mention any four properties of thermal radiation.
Answer:
The energy omitted by a body on account of its temperature is called thermal radiation.
Properties of thermal radiations :

• They ate transverse wave in nature and travel in free space.
• They can be reflected and refracted.
• They do not heat intervening medium through which they pass.

Question 32.
Arrive at an expression for the time period of a simple pendulum.
Answer:
The tangential component of force mg is mg sinθ.
Torque: -L(mgsinθ) = Iα

VI. Answer any THREE of the following questions : ( 3 × 5 = 15 )

Question 33.
On a two – lane road, Car A is travelling with a speed of 36kmph. Two cars B and C approach car A in opposite directions with a speed of 54 kmph each. At a certain instant, when the distance AB is equal to AC, both being 1km, B decides to overtake A before C does. What minimum acceleration of car B is required to avoid an accident?
Answer:
Speed of car A = 36 km/h = 36 × \(\frac{5}{18}\) = 10 m/s
Speed of car B = speed of car C = 54 km / h = 54 × \(\frac{5}{18}\) =15 m/s
Relative speed of car B with respect to car A is,
v = 15 – 10 = 5 m/s
relative speed of car C with respect to car A is
V_CA = 15 + 10 = 25 m/s
AB = AC = 1 km = 1000m
w.k.t: s = ut
\(t=\frac{s}{u}=\frac{\mathrm{AC}}{\mathrm{V}_{\mathrm{AC}}}=\frac{1000}{25}=40 \mathrm{s}\)
Let ‘a’ be the acceleration of car ‘B’ for time t = 40s.
w.k.t
s = ut + \(\frac{1}{2}\) at²
1000 = 5 × 40 + \(\frac{1}{2}\) × a × 40 × 40
1000 = 200 +800a
∴ 800 a = 800
a = 1 ms^-2

Question 34.
A batsman deflects a ball by an angle of 45° without changing its initial speed which is equal to 54 kmph. What is the impulse imparted to the ball? If the time of contact . between the hall and the bat is 0.01s, what is the average force exerted by the bat on the ball? (Mass of the ball is 0.15 kg.)
Answer:
Initial momentum of ball = mu
= \(\frac{0.15 \times 54 \times 1000}{3600}\) = 0.15 × 15 = 2.25 kgms^-1
Final momentum of ball = mu cos θ
= 2.25 × 0.707 ; cos 45° = 0.77 = 1.59 kg ms^-1.
Impulse = 1.59 – 2.25 = – 0.66 kg ms^-1
if Δt = 0.01s
average force F = \(\frac{\text { Impulse }}{\Delta t}=\frac{-0.66}{0.01}=-66 \mathrm{N}\)
F = -66N on the ball and + 66N on the bat

Question 35.
A rope of negligible mass is wound round a hollow cylinder of mass 3 kg and radius 40 cm. What is the angular acceleration of the cylinder if the rope is pulled with a force of 30 N? What is the linear acceleration of the rope? Assume that there is no slipping.
Answer:
m = 3 kg
r = 40cm = 0.4m
F = 30N
The moment of inerties of the hallow cylinder about its geometer axis.
I = mr²
I = 3 × (0.4)²
I = 0.48 kg m²
(i) angular acceleration
w.k.t τ = Iα
But τ = 30 × 0.4
∴τ = 12Nm
∴ α = \(\frac{\tau}{\mathrm{I}}\)
α = \(\frac{12}{0.48}\) = 25 rad s^-1
(ii) liner acceleration
a = rα
a = 0.4 × 25
a = 10.0 ms^-2

Question 36.
A steam engine delivers 5.4 × 10⁸J of work per minute and services 3.6 × 10⁹Jof heat per minute From its boiler. What is the efficiency .of the engine? How much heat is wasted per minute?
Answer:
Work done by the steam engine per minute (W) = 5.4 × 10⁸J Heat supplied from the boiler
H = 3.6 × 10⁹J
Efficiency of the engine = \(\frac{\text { Output energy }}{\text { Input energy }}\)
∴η = \(\frac{W}{H}=\frac{5.4 \times 10^{8}}{3.6 \times 10^{9}}\)
∴η = 0.15
Hence the percentage efficiency of the engine is 15%
The amount of heat wasted = 3.6 × 10⁹ – 5.4 × 10⁸ = 36 × 10⁸ – 5.4 × 10⁸
= 30.6 × 10⁸J

Question 37.
A train, standing at the outer signal of a railway station blows a whistle of frequency 400 Hz in still air. (i) What is the frequency of the whistle for a platform observer when the train (a) approaches the platform with a speed of 10 ms^-1, (b) recedes from the platform with a speed of 10 ms^-1? (ii) What is the speed of sound in each case? The speed of sound in still air can be taken as 340 ms^-1.
Answer:
Given f=400 Hz, v_w = 10 ms^-1, v = 340 ms^-1.
speed of sound = v + v_w = 340 + 10 = 350 ms^-1,
λ = \(\frac{v}{f}=\frac{340}{400}=0.85 \mathrm{m}\)
(i) Apparent frequency of sound f‘= \(\frac{\mathrm{fv}}{\left(\mathrm{v}+\mathrm{v}_{\mathrm{w}}\right)}\)
Here v₀ =0 and v_s = 0
i.e., f’ = \(\frac{400 \times 340}{350}\) = 388.6 Hz
f’ ≈ 389 Hz
New wavelength of sound λ’
λ’ = \(\frac{v+w}{f}=\frac{350}{400}\)
i.e. λ’ = 0.875 m
Speed of sound as heard by an observer will be 350 ms^-1 and
Δλ = 0.875 – 0.850 = 0.020 m.
(ii) When the air is still v_w = 0

i.e. λ’ = λ
There will be no change in the wavelength of sound w.r.t. the observer in motion. Relative velocity of sound w.r.t the observer = 350 ms^-1.

Students can Download 1st PUC Physics Model Question Paper 1 with Answers, Karnataka 1st PUC Physics Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

Karnataka 1st PUC Physics Model Question Paper 1 with Answers

Time: 3.15 Hours
Max Marks: 70

General Instructions:

1. All parts are compulsory.
2. Draw relevant figure / diagram wherever necessary.
3. Numerical problems should be solved with relevant formulae.

Part – A

I. Answer the following questions: ( 10 x 1 = 10 )

Question 1.
Write the dimensional formula for Pressure.
Answer:
[pressure] = [M¹ C^-1T^-2]

Question 2.
When does the circular motion become uniform?
Answer:
The circular motion of bodies will be uniform, for uniform speed of particles.

Question 3.
What is the amount of work done by the gravitational force on the body moving on the horizontal plane?
Answer:
Zero

Question 4.
What is elastic collision?
Answer:
A collision in which linear momentum and kinetic energy of the interacting system are conserved, is known as an elastic collision.

Question 5.
Give one example for elastomers.
Answer:
Rubber

Question 6.
What is thermal stress?
Answer:
When thermal expansion is not allowed in a solid, the corresponding stress developed in it is known as thermal stress. The solid acquires a compressive strain due to the external forces, provided by (say) the rigid support at one end of it.

Question 7.
Define mean free path of the molecule in the gas.
Answer:
The average distance traveled by the molecule during two consecutive collisions is called mean free path.

Question 8.
Where does Kinetic energy of the oscillating particle become maximum?
Answer:
The K.E of oscillating particle becomes maximum when it reaches the mean position.

Question 9.
What is resonance?
Answer:
If the frequency of forced oscillation of a system is the same as the natural frequency of the system which induces oscillation in the other, then both the systems are said to be in resonance.

Question 10.
Give the value of phase difference between the particles of adjacent loop of stationary wave.
Answer:
Φ = 180°

Part – B

II. Answer any five of the following questions:  ( 5 x 2 = 10 )

Question 11.
Name any two fundamental forces of nature.
Answer:

• Gravitational force
• Electro – weak force
• Strong nuclear force

Question 12.
Mention any two sources of systematic error.
Answer:

• Instrumental error.
• Personal error.

Question 13.
Draw position time graph for the particle having zero acceleration.
Answer:

Question 14.
Write the equation for maximum horizontal range in projectile motion and explain the terms.
Answer:
R = \(\frac{u^{2} \sin 2 \theta}{g}\)
Where u – initial speed,
θ – angle of projection
g – acceleration due to gravity
R – Horizontal range

Question 15.
Mention any two methods of reducing friction.
Answer:

1. Wear and tear can be minimised by polishing the surfaces and lubricating machinery parts with oil and grease etc.
2. Streamlining the bodies reduce fluid (air or water) resistance.

Question 16.
Mention the conditions for the body in mechanical equilibrium.
Answer:
(1) The vector sum of the forces on the rigid body is zero for translatory equilibrium
\(\sum_{i=1}^{n} \vec{F}_{i}=0\) and (acceleration a = 0 )
(2) The vector sum of the torques on the rigid body is zero for rotatory equilibrium (a=0) i.e.

i.e. the components of X, Y and Z independently vanish to zero for linear equilibrium.

Sum of X components, Y components and Z components of torque on the particles, vanish for rotational equilibrium.

Question 17.
State and explain Hooke’s law.
Answer:
Statement: The ratio of stress to strain is a constant for a material within the elastic limit.
Modulus of elasticity = \(\frac{\text { Stress }}{\text { Strain }}\)

Within the elastic limit, stress v/s strain is a straight line ‘A’ is the elastic limit upto which Hooke’s law is applicable. Beyond ‘B’ the yielding point, the wire extends but does not return to the initial state when the deforming force is removed. ‘F’ is the breaking point. ‘EF’ allows the material to be malleable and ‘DE’, ductile.

Question 18.
What are extensive thermodynamical variables? Give one example.
Answer:
Internal energy, volume, mass are called extensive thermodynamic variables.

Part – C

III. Answer any FIVE of the following questions : ( 5 x 3 = 15 )

Question 19.
Obtain.the equation for maximum height in projectile motion.
Answer:
We know that (v_ocosθ) remains constant.
Instantaneous distance along the horizontal is given by ,
x = (v_ocosθ)t
for x = R (range of the projectile), t = T = time of flight.

Question 20.
State and prove the law of conservation of linear momentum.
Answer:
Statement: In an isolated system of collision of bodies, the total linear momentum before impact is equal to the total linear momentum after impact.

Let m₁ and m₂ be the masses of two bodies moving along \(\vec{v}_{1 i}\) and \(\vec{v}_{2 i}\). Let \(\vec{v}_{1 f}\) and be the \(\vec{v}_{2 f}\) be final velocities after the impact.
At the time of impact the force of action acts on the body B and the force of reaction acts on A.
Applying Newton’s III law of motion
\( |Force of action on \mathrm{B}|=-| Force of reaction on \mathrm{A} |\)

This shows that the total final linear momentum of the isolated system equals its total initial momentum.

Question 21.
Prove the work energy theorem in the case of constant force.
Answer:
w.k.t work done W = \(\overrightarrow{\mathrm{F}} \cdot \overrightarrow{\mathrm{s}}\)
where F = ma, s = \(\frac{v^{2}-u^{2}}{2 a}\)
W = \(\overrightarrow{\mathrm{F}} \cdot \overrightarrow{\mathrm{s}}\) becomes
W = \(\frac{m\left(v^{2}-u^{2}\right)}{2}\)
or W = K_f – K_i
or W = Δ K.E
Thus, work come by a constant force is equal to the difference in the K.E of the body.

Question 22.
Obtain the equation for moment of couple.
Answer:
Two equal and opposite forces acting at two different points constitute couple. The moment of couple is measured by taking the product of magnitude of any one force and the arm of the couple.

Hence moment of couple = \(\overrightarrow{\mathrm{F}}|\overrightarrow{\mathrm{OA}}|+\overrightarrow{\mathrm{F}}|\overrightarrow{\mathrm{OB}}|=\overrightarrow{\mathrm{F}}(\mathrm{OA}+\mathrm{OB})=\overrightarrow{\mathrm{FAB}}\)

Question 23.
Derive equation for acceleration clue to gravity on the surface of the earth.
Answer:
Let M be the mass of the Earth and R be its radius.
We know that F = \(-\frac{\mathrm{GMm}}{\mathrm{r}^{2}}\)
where ‘m’ is a mass body very close to the surface of the Earth.
Force of gravity on the mass ‘m’ is F’ = mg
However F = F’
Therefore mg = \(\frac{\mathrm{GMm}}{\mathrm{R}^{2}}\)
i.e, g = \(\frac{\mathrm{GM}}{\mathrm{R}^{2}}\)

Question 24.
Show that volume co-efficient of expansion of ideal gas is inversely proportional to absolute temperature.
Answer:
At constant pressure, V ∝ T
i.e., V = KT. For an increase in the temperature ∆T, the corresponding increase in the volume of the gas will be ∆W.
i.e., (V + ∆V) = K(T + ∆T)
i.e., ,V + ∆V = KT+ K∆T
i.e., \(\frac{\Delta \mathrm{V}}{\Delta \mathrm{T}}=\mathrm{K}=\frac{\mathrm{V}}{\mathrm{T}}\)
or
\(\frac{\Delta \mathrm{V}}{\mathrm{V} \Delta \mathrm{T}}=\frac{1}{\mathrm{T}}=\gamma\)
where r is volume co-efficient of an ideal gas

Question 25.
Show that C_v = \(\frac{3}{2} \mathbf{R}\) for mono atomic gas.
Answer:
(dQ) = du = C_v dT
ie. C_v dT = \(\frac{f \mathrm{R} d \mathrm{T}}{2}\)
∴ C_v = \(\frac{f R}{2}\) for mono atonic gas, f = 3
C_v = \(\frac{3 \mathrm{R}}{2}\)

Question 26.
Give any three differences between progressive wave and stationary wave.
Answer:

• Progressive waves transfer energy, whereas stationary waves do not.
• No particles of the medium are in a state of rest in a PW but in a SW, the particles at nodes will be at rest.
• The particle velocities will remain the same for a given displacement in a PW, whereas in a SW, particles at nodes will have zero speed and at anti-nodes, particles have maximum speed.
• y = f(x, t) for a PW and y = f(x) g(t) for a SW.
• Distance between two points at which particles have same state of vibration is called , wavelength in a PW whereas distance between two consecutive nodes or anti-nodes is half the wavelength.

Part – D

IV. Answer any TWO of the following questions : ( 2 x 5 = 10 )

Question 27.
Derive equation for centripetal acceleration.
Answer:
Let \(\vec{r}\) and \(\vec{r}^{\prime}\) be the position vectors and \(\vec{v}\) and \(\vec{v}^{\prime}\) veIocities of the object when it is at point P and P’. By definition, velocity at a point is along the tangent at that point in the direction of the motion. Since the path is circular \(\vec{v}\) is perpendicular to \(\vec{r}\) and \(\vec{v}^{\prime}\) is perpendicular to \(\vec{r}^{\prime}\).
Therefore, ∆\(\vec{v}\)is perpendicular to ∆\(\vec{r}\) Average acceleration \(\frac{\Delta \vec{v}}{\Delta t}\) is perpendicular to ∆\(\vec{r}\).
The magnitude of \(\vec{a}\) is, by definition, given by \(|\vec{a}|=\lim _{\Delta t \rightarrow 0} \frac{|\Delta \vec{v}|}{\Delta t}\)
The triangle formed by the position vectors is similary to the triangle formed by the velocity vectors.

lf ∆t is very small. ∆ will also small. The arc PP is approximately equal to \(|\Delta \vec{r}|\)
i.e., \(\lim _{\Delta t \rightarrow 0} \frac{|\Delta \vec{r}|}{\Delta t}\) = v. Thus, centripetal acceleration \(|\vec{a}|=\frac{v}{r} v=\frac{v^{2}}{r}\) and \(\vec{a}=\frac{v}{r} \frac{d \vec{r}}{d t}\).
The centripetal acceleration is always directed towards the centre. The centripetal force = ma.

Question 28.
Prove “law of conservation of mechanical energy” for freely falling body.
Answer:
Energy can neither be created nor destroyed but can be transformed into other forms of energy.
Let a particle be at ‘C’. Initially the particle w ill be zero velocity. Let ‘h’ be the height of the particle.

P.E_c = mgh, K.E_c = 0
T.E = mgh
At B, K.E = \(1 / 2 \mathrm{mv}_{\mathrm{B}}=1 / 2 \mathrm{m}(2 \mathrm{g} x)=\mathrm{mg} x\)
P.E_B = mg (h – x)
Hence T.E = (mgh – mgx) + (mgx)
= mgh
At A, v_A²= 2gh
So that K.E = \(\frac{1}{2}\) m2gh = mgh
P.E_A = O.
Hence at all points A, B and C, the total energy is conserved.

Question 29.
Obtain equation for Kinetic energy of rolling motion.
Answer:
K.E of rolling body = Transiatory K.E + Rotational K.E

V. Answer any TWO of the following questions : ( 2 x 5 = 10 )

Question 30.
State and prove Bernaulli’s theorem.
Answer:
Along a steam line, in a steady flow of non viscous fluid, potential energy, kinetic energy and pressure energy remain constant.
i.e., \(\mathrm{mgh}+1 / 2 \mathrm{mv}^{2}+\mathrm{PV}=\mathrm{K}\)
i.e., \(\mathrm{mgh}+1 / 2 \mathrm{mv}^{2}+\mathrm{Pm} / \rho=\mathrm{K} \div \mathrm{m}\)
we get, \(g h+\frac{v^{2}}{2}+\frac{P}{\rho}=K \div g\)
i.e., \(\mathrm{h}+\frac{v^{2}}{2 g}+\frac{\mathrm{P}}{\rho g}=\mathrm{K}\)
where h is called gravitational head, \(\frac{v^{2}}{2 g}\) is velocity head and \(\frac{P}{\rho g}\) is pressure head.
For a horizontal Flow, \(\frac{\rho v^{2}}{2}+\frac{P}{\rho g}\) = K
As the velocity of the fluid increases, pressure of the fluid decreases.

Question 31.
What is isothermal process? Obtain equation for work done in isothermal process.
Answer:
The process in which changes in pressure and volume of a gas system takes place at constant temperature of the system, is known as isothermal process.
For an isothermal process, PV = constant.
At any intermediate stage with pressure P and change in volume from V to V + dV,
work done dw = P dV. However for the entire process W = \(\int_{V_{1}}^{V_{2}} P d V\) .

For V₂ > V₁, W > 0 and for V₂ < V₁, W < 0.
In an isothermal expansion, the gas absorbs heat and does work, while in an isothermal compression, work is done on the gas by the environment and heat is released.

Question 32.
What is closed pipe? Show that modes of vibration in closed pipe are odd harmonics.
Answer:
Let ‘L’ be the length of the closed pipe. A pipe with one end closed is known as a closed pipe system. Le V be the velocity of sound in air. Length of half segment = \(\frac{\lambda_{0}}{4}\)
i.e., L = \(\frac{\lambda_{0}}{4}\) i.e., λ₀ = 4L.

The least mode of vibration is called fundamental mode i.e.,
fundamental frequency f₀ = \(\frac{\mathbf{v}}{\lambda}=\frac{\mathbf{v}}{4 L}\)
In the second mode of vibration.

i.e., f₂ = \(\frac{5 v}{4 L}\)
Hence f₀ : f₁ : f₂ :……..: f_n : : 1 : 3 : 5 :………: (2n – 1)

VI. Answer any THREE of the following questions : ( 3 x 5 = 15 )

Question 33.
A car moving along a straight road with speed of 144 Kmh is brought to a stop within a distance of 200 m. What is the retardation of the car and how long does it take to come to rest?
Answer:
Given u = 144 kmh^-1
ie., u = \(\frac{144 \times 5}{18} \mathrm{ms}^{-1}\)
ie., u = 40 ms^-1
v = 0, s = 200 m, a = ?   t = ?
w.k.t v² = u² + 2aS
i.e., 0 = (40)² + 2a(200)
a = \(\frac{-1600}{400}\)
a = -4ms^-2
By using, v = u + at,
0 = 40 – 4t
i.e, t = \(\frac{40}{4}\) =10 s
Hence time taken by the car to stop
t = 10s

Question 34.
A circular racetrack of radius 200 m is banked at the angle of 10°. If the coefficient of friction between the wheels of racecar and the road is 0.15 what is the
(a) optimum speed of the race car to avoid wear and tear on its tyres?
(b) maximum permissible speed to avoid slipping? [Given: Acceleration due to gravity on the earth = 9.8 ms^-2]
Answer:
(i) Give r = 200 m, θ = 10°, μ = 0.15
v = v_max = ?   g = 9.8 ms^-1
w.k.t  v_max = \(\sqrt{\frac{r g(\mu+\tan \theta)}{(1-\mu \tan \theta)}}\)

Question 35.
If the weight of a 4 kg mass on the surface of the earth is 39.2 N, calculate the acceleration due to gravity of earth at
(a) 32 km height from the surface of the earth.
(b) 16 km depth from the surface of the earth. [Given : Radius of earth = 6400 km]
Answer:
Given m = 4kg, F = W = 39.2 N
(i) with attitude
\(g^{\prime}=g\left(1+\frac{h}{R}\right)^{-2}\)
given g = 10ms^-1, h = 32 km, h <<R
hence g¹ = g(1 – 2h/R)
i.e., g¹ = 9.8 \(\left(1-\frac{2 \times 32}{6400}\right)\) = 9.8 x 0.99
g¹ =9.702 ms^-2
(ii) with depth; g¹ = g( 1 – h/R)
i.e., g¹ = 9.8 \(\left(1-\frac{16}{6400}\right)\)
i.e., g¹ = 9.8 x 0.9975
g¹ = 9.775 ms^-2

Question 36.
A copper block of mass 2.5 kg is heated in a furnace to a temperature of 500°C and then placed on a large ice block. What is the maximum amount of ice that can melt?
Answer:
Given m = 2.5 kg θ₁ = 500°C, θ₂ = 0°C
C_s =0.39 x 10³ Jkg^-1k^-1
L = 3.35 x 10⁵ Jkg^-1,  μ_ice = ?
Since m_ice = C_s Δ θ = m_iL

i.e., m_ice = 1.455 kg

Question 37.
A body oscillates with SHM according to the equation (in SI units)
x = 5 cos \(\left(3 \pi+\frac{\pi}{4}\right)\)
Calculate : (a) frequency of oscillation (b) amplitude of oscillation (c) Displacement of oscillation at t = 1s
Answer:
given,  x = 5 cos (3πt + π/4)m,
f = ?   A = ?   x = ?   when t = 1s
Comparing this with x = A cos (wt + Φ) we get,
(i) A = 5m
(ii) w = 3π rad.s^-1
i.e., 2πf= 3π
∴ f = 3/2 = 1.5Hz
(iii) x = 5 cos (3π( 1) + π/4)
i.e x = 5 cos (13π/4)
x = 5 cos (360° + 225°)
i.e x = 5 cos (225°)
i.e x = 5 cos (180°+ 45°)
x = -5 cos 45°
i.e, x= \(-5 / \sqrt{2}\) = -3.535 m

 

Students can Download 1st PUC Chemistry Model Question Paper 5 with Answers, Karnataka 1st PUC Chemistry Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

Karnataka 1st PUC Chemistry Model Question Paper 5 with Answers (Old Pattern)

Time: 3.15 Hours
Max Marks: 70

Instructions:

1. The questions paper has four parts A, B, C and D.
2. In part A each question carries ONE Marks. In part B, each question carries TWO marks, in part C each question carries FIVE marks. In Part D-1 carries TEN Marks and each question in D -2 carries FIVE marks.
3. Write balanced chemical equations and draw diagram wherever necessary.

Part – A

I. Answer of all the following questions: ( 1 × 9 = 9 )

Question 1.
What is a limiting reagent in a reaction ?
Answer:
The reactant which gets completely consumed or limits the amount of product formed in a reaction

Question 2.
State the law of conservation of mass.
Answer:
It states that matter can neither be created nor be destroyed

Question 3.
Select an isoelectronic pair among the following Na⁺,Cl^–,F^–,Li⁺
Answer:
Na⁺ ,F^–

Question 4.
What is the effect of temperature on Viscosity of liquids ?
Answer:
Viscosity of liquids decrease as temperature rises.

Question 5.
A closed thermos flask containing hot coffee represents what type of a system ?
Answer:
Isolated.

Question 6.
Write the expression for Kc for the equilibirium, N_2(g) + 3H_2(g) ⇌ 2NH_2(g)
Answer:
\(\mathrm{K}_{\mathrm{c}}=\frac{\left[\mathrm{NH}_{3}\right]^{2}}{\left[\mathrm{N}_{2}\right]^{1}}\)

Question 7.
H₂⁺and H₂^–have same bond order but H₂⁺is more stable than H₂^–, why ?
Answer:
H₂^–has en electron in antibonding MO which makes it less stable than H₂⁺

Question 8.
What volume of O₂ is produced by 1 litre of “10 volume” H₂O₂ at STP ?
Answer:
10 litres.

Question 9.
Name the alkali metal which is radioactive ?
Answer:
Francium (Fr)

Question 10.
Which element is diagonally related to lithium ?
Answer:
Magnesium (Mg)

Question 11.
Give an example for a Heterocyclic compound.
Answer:
Pyridine, Furan, Thiophene.

Part – B

II. Answer any Five questions: ( 5 × 2 = 10 )

Question 12.
Write balanced chemical equation for the combustion of methane. How many mole of methane are required to produced 88g Carbon dioxide by the combustion of Methene ?
Answer:
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
\(\begin{array}{cc}{12+4 \times 1} & {12+2 \times 16} \\{16 g} & {44 g}\end{array}\)
44g of CO₂ requires 16g of CH₄.
88g of CO₂ requires ?
= \(\frac{88 \times 16}{44}\) = 32g of CH₄ = 2 mole of methane.

Question 13.
Size of Na⁺ ion is smaller than Na. Give reason.
Answer:
During the formation of Na⁺ ions effective nuclear charge increases thus electron cloud shrinks.

Question 14.
What causes temporary and permanent hardness of water ?
Answer:
Temporary Hardness – presence of dissolved Bicarbonates of Mg and Ca.
Permanent Hardness – Presence of dissolved Chlorides and sulphates of Mg and Ca.

Question 15.
Derive Ideal gas equation using gas laws.
Answer:
From Boyle’s law V ∝ \(\frac{1}{p}\) ………..(1)
From Charle’s law V ∝ T  ………..(2)
From(1) and (2)
V ∝ \(\frac{T}{p}\)
PV ∝ T
Or PV – RT

Question 16.
(i). Chemical equilibrium is dynamic. Give reason.
Answer:
Both forward and backward reactions are occurring at the same rate.

(ii). What is the effect of a Catalyst on the equilibrium of a reversible reaction.    2
Answer:
A catalyst has no effect on the position of equilibrium but it helps the reaction to attain equilibrium quickly.

Question 17.
Diamond is a bad conductor of electricity but Graphite is a good conductor. Justify the statement.
Answer:
Due to sp³ hybridization in Diamond no free electrons are present.
In Graphite due to sp³ hybridization, there are free electrons to conduct electricity.

Question 18.
Write any two common chemicals of photochemical smog.
Answer:
Ozone, Nitric oxide, Acrolein, Frmaldehyde and peroxy acetyl nitrate.

Part – C

Note : Answer any Four questions: ( 4 × 4 = 16 )

Question 19.
a. Define mole fraction.
Answer:
It is ratio of number of moles of a particular component to the total number of moles
of the solution. Mole fraction = \(\frac{\mathbf{n}_{\mathrm{B}}}{\mathbf{n}_{\mathrm{A}}+\mathbf{n}_{\mathrm{B}}}\)

b. Calculate the mass percent of the solute, if 4 g of a solute is dissolved in 18g of water.
Answer:

Question 20.
a. Explain the formation of line spectrum of Hydrogen based on Bohr’s atomic theory. Write the energy level diagram for Lyman and Balmer series of the hydrogen spectrum.
Answer:
According to Bohr’s Atomic model:
A sample of H₂ gas contains large number of hydrogen molecules. When electric discharge is passed through hydrogen gas the molecules absorbs energy and split up into atoms. Now the electron present in different atoms absorbs different energy and jump to different high energy state. The electrons in the higher energy is unstable thus returns back by emitting radiations having different wavelength. Hydrogen spectrum consists of many spectral lines event through the hydrogen only one electron.

Lymon series : The lines obtained when and electron jumps from 2nd, 3rd, 4th…. i.e., from any higher energy level to first energy level (n₁ = 1) are called Lyman series. These lines are found in ultraviolet region.

Balmer series : The lines obtained when electrons jumps from 3rd, 4th 5th… from any higher energy level to second energy level are called Balmer series. This is found in visible region.

Or (Internal choice)

b. (i) Calculate the wavelength of a ball of mass 0.05 kg moving with a velocity of 5ms^-1. Given : h = 6.626 × 10^-34 Js.               2+2
Answer:

Question 21.
a. Classify the following physical quantities having α Extensive and Intensive properties Mass, Density, Temperature and Heat capacity.
Answer:
Extensive property – Mass, Heat capacity
Intensive property – Density, Temperature

b. State Hess’s law of constant summation.
Answer:
Hess’s law : .Whether a chemical reaction takes place in a single step or in several steps, the total change in enthalpy remains the same. Consider the formation of CO₂ from C.

Question 22.
Using Le-Chatelier’s principle explain the effect of
(i) Addition of CH₄ (ii) Addition of CS₂ (iii) Removal of S₂ (iv) Removal of H₂S on the equilibrium,
CH_4(g) + 2S_2(g) ⇌ CS_2(g) + 2H₂S_{(g)                          4}
Answer:
i) Increase in concentration of CH₄ , favours forward reaction.
ii) Increase in concentration of S₂, favours backward reaction.
iii) Decrease in concentration S₂, favours backward reaction.
iv) Decrease in concentration of H₂S , favours forward reaction.

Question 23.
a. Give the composition of Washing soda. An aquous solution of washing soda is alkaline, Give reason.
b. What happens when Cl₂ (Chlorine) gas is passed into milk of Lime ? Write the equation.   2+2
Answer:
Bleaching powder is formed.
2Ca(OH)₂ + 2Cl₂ → CaCl₂ + Ca(OCl)₂ + 2H₂O

Question 24.
Draw a neat labeled diagram and give the calculations involved in the estimation of Nitrogen in an Organic compound by Duma’s method.
Answer:
Principle : The organic compound containing nitrogen when heated with excess of copper oxide in the atmosphere of carbon dioxide, yields nitrogen in addition to carbon dioxide and water.

Traces of nitrogen oxides formed during combustion of organic compound are reduced to nitrogen by passing the gaseous mixture over a heated copper gauze. The percentage of nitrogen present in a given organic compound is calculated from the volume of nitrogen collected over potassium hydroxide solution from a known mass of organic compound.

Procedure : The apparatus used for the estimation of nitrogen by this method is shown in the figure.

A known mass of organic compound is mixed with copper oxide and placed in the combustion tube. The carbon dioxide gas is passed through the combustion tube to displace air present in the tube. The combustion tube is now heated in the furnace. the nitrogen evolved collects in the nitrometer. The volume of the nitrogen collected is recorded after adjusting the levels of potassium hydroxide solution in the two limbs are equal. Room temperature and atmosphere pressure are recorded.

Calculation:
Mass of organic compound = mg
Volume of nitrogen in nitrometer = V cm³
Room temperature = t° C = (273 + t) K
Atmosphere pressure = P₁ mm
Aqueous tension at room temperature = P′ mm
Pressure of dry nitrogen gas formed = P = (P – P′) mm
Volume of nitrogen at STP (V₀) = \(\frac{\mathrm{PV} \times 273}{760 \times(273+\mathrm{t})} \mathrm{cm}^{3}\)
22,400 cm³ of nitrogen of STP = 28 g of nitrogen
Mass of V₀ cm³ of nitrogen = \(\frac{28 \times V}{22,400} g\)
Percentage of nitrogen =\(\frac{28 \times V_{0} \times 100}{22,400 \times m}\)

Part – D

Note : Answer any Four questions : ( 2 × 5 = 10 )

Question 25.
a. (i) Name the isotope of Hydrogen containing two neutrons.
(ii) Mention any two limitations of Bohr’s atomic theory.
b. Atomic number and Mass number of an element are 29 & 64. How many protons and Neutrons are present in it? Why the Electronic configuration of the element.
Answer:
a) i) Tritium (₁T³)
ii) It fails to account for the finer details of the hydrogen atom spectrum observed by using sophisticated spectroscopic technique, i.e., stark effect and zeeman effect.

b) It could not explain the ability of atoms to form molecules by chemical bonds.

Question 26.
a. Explain the shape of Ammonia molecule using VSEPR theory.
Answer:
Ammonia (NH₃)
Electronic configuration of N: 1s² 2s² 2p³
Valance orbital representation

1. when 2s² orbital hybridised with 2p_x, 2p_y, and 2p_z forms the following sp³ hybridised structure.
2. In 2s² orbital, the electrons are paired up hence they are not involved in bond formation called loan paired of electron (L.P).
3. When sp³ hybridized N combines with 3 hydrogen atom, forms pyramidal structure of ammonia.
   Pyramidal structure angle = 107°

Or (Internal Choice)

Mention any three postulates of Molecular Orbital Theory.
Answer:

1. The electrons in an atom are found in atomic orbitals, the electrons in a molecule are found in molecular orbitals.
2. The molecular orbitals are formed by the combination of atomic orbitals of comparable energies and proper symmetry.
3. The BMO has lower energy and hence greater stability than the corresponding ABMO.
4. The molecular orbitals are filled by electrons in accordance with Aufbau principle, Pauli’s exclusion principle and the Hund’s rule.

b. Lithium molecule has 4 electrons in bonding molecular orbital and 2 electrons in anti bonding molecular orbital. Write the electronic configuration and calculate the bond order of Lithium molecule.
Answer:

Or (Internal choice)

Calculate the Bond order, show that Helium Molecule (He₂) does not exist.
Answer:

Reason: since bond order is 0 the molecule does not exist.

Question 27.
a. For the oxidation of Iron : 4Fe_(s) + 3O_2(g) → 2Fe₂O_3(g)
Entropy change and Enthalpy change at 298 K are – 549.4 J/K/mol and -1648 × 10³ J/mol respectively. Calculate the free energy change for the reaction. Is the reaction spontaneous at 298 K.
Answer:
∆G = ∆H – T∆S
∆G = -1648000 + 163721.2
= -1484278.8 J/mol
=-1484.2788 kjmol
The reaction is spontaneous.

b. Define Enthalpy of solution.
Answer:
The enthalpy of solution at infinite dilution is the enthalpy change observed an dissolving the substance in an infinite amount of solvent when the interations between the ions are negligible.

Question 28.
a. In the Galvanic cell, the cell reaction is Zn_(s) + 2Ag_(aq)⁺ → Zn²⁺+ 2Ag_(a)
(i) Which of the electrode is the Anode ?
(ii) Write the Cathodic and Anodic reactions.
(iii) Identify the oxidizing and reducing agents.
Answer:
i) Zn elelctrode.

ii) Cathodic reaction : Ag⁺+e^– → Ag
Anodic rection : Zn – 2e^– → Zn²⁺

iii) Oxidising agent: Ag⁺
Reducing agent: Zn

b. Show that the reaction CaCO₃ → CaO + CO₂ is not a Redox reaction.    3+2
Answer:

Since there is not change in oxidation state of any element before and after the reaction. It is not a redox reaction.

Question 29.
a. Explain the Ampoteric nature of Aluminium, give equations.
Answer:
Aluminium reacts both with acid and base so it behaves as amphoteric nature.
2Al(s) + 6HCl(aq)  → 2Al³⁺(aq) + 6Cl^–(aq) + 3H₂(g) behaving as acid.
2Al(s) + 2NaOH(aq) + 6H₂O(l) → 2Na⁺[Al(OH)₄]^– (aq) + 3H₂(g) behaving as base.

b. Name the type of hybridization of
(i) Boron in Diborane
(ii) Carbon in Graphite
Answer:
i) sp³ hybridization
ii) sp² hybridisation

Question 30.
a. Explain the mechanism of chlorination of Methane, with equations.
Answer:
Mechanism of chlorination of methane involves three types.
Step 1 : Initiation : Chlorine absorbs energy and undergoes homolysis to give chlorine free radicals.

Step 2 : Propagation : Chlorine free radical reacts with methane to give methyl free radical.
Cl^• + CH₄ → CH₃^•+ HCl
The methyl free radical reacts with chlorine to form methyl chloride and chlorine free radical.
CH₃^•+ Cl₂ → CH₃Cl + Cl^•

Step 3 : Termination : Free radicals combine to form stable products.
Cl^• + Cl^• → Cl₂ (Chlorine)
CH₃^•+ Cl^• → C₂H₆ (Ethane)
CH₃^• + Cl^• → CH₃Cl (Methyl Chloride)

b. How do you convert Benzene to Benzene hexachloride (BHC) ? 3+2
Answer:

Under ultra violet light, three chlorine molecules add to benzene to produce benzene hexa chloride, C₆H₆Cl₂ which is also called gammaxane.

Part – E

Answer any Three of the following questions: ( 3 5 = 15 )

Question 31.
a. (i) Explain why BF₃ molecule has zero dipole moment although the B-F bonds are polar ?
(ii) Alkali metals and Halogens form Ionic compounds. Give reason.
Answer:
i) Shape of BF₃ is Trigonal planar.
The net sum of bond moment is equal to zero because of cancellation of bond moments due to symmetry in the molecule.

ii) Alkali metals have low ionization enthalpy hence they easily form cations.
Halogens have high electron gain enthalpy hence they easily form Anions.

b. What is Hydrogen bonding ? Sketch the Hydrogen bonding in liquid Hydrogen fluoride ?   3+2
Answer:
It is an electrostatic force of attraction between an electropositive element and electronegative element Hs⁺-Fs.

Question 32.
a. Write the expression for the compressibility factor (Z) for one mole of a gas and name the terms in it. What is the value of Z for an ideal gas ?
Answer:
z = \(\frac{p v}{R T}\)    z = compressibility, P = pressure, V = Volume, T = Temperature in K, Z = 1 for ideal gas, R = Universal gas constant.

b.A balloon is filled with Hydrogen gas at room temperature. It will burst if pressure exceeds 0.2 bar. If at 1 bar pressure the gas occupies 2.27 liter volume, up to what volume can the balloon be inflated ?
Answer:

Question 33.
a. What is a Bronsted – Lowery Acids ? Identify the two Conjugate acid-base pairs in the following.
NH₃ + HCl ⇌ NH₄⁺+ Cl^–
Answer:
Bronsted – lowery theory
An acid is substance which donates proton base is a substance which accepts a portion so this theory is also called as proton theory.

Conjugate acid base pair

b. Calculate the solubility of Lead Chloride at 298. K, if its solubility product is 1.6 × 10^-5.
Ans: For PbCl₂k_sp = 4s³

Question 34.
a. Write any two differences between Resonance effect and Electromeric effect.
Answer:

Resonance Effect	Electromeric Effect
1. It takes place in conjugated double bond system	1. It takes place in the molecule having c = c
2. It is a permanent effect takes place in absence of attacking reagent.	2. It is temporary effect takes place in presence of attacking reagent.

b. What type of structural isomerism is exhibited by the Propanone and Propanal pair ?
Write their structural and identify the functional groups present in them.      2+3
Answer:
Functional isomerism
Structure : CH₃ – CO – CH₃, CH₃ – CH₂ – CHO
Functional groups : Ketone (C = O); Aldehyde (-CHO)

Question 35.
a. (i) Name the chief product obtained when Benzene is heated with concentrated Sulphuric acid. Give equation ?
Answer:
Benzene Sulphonic Acid
Suiphonation : Benzene reacts with concentrated sulphuric acid at 80°C to form benzene suiphoric acid.

Mechanism : This involves the following steps.
Step 1 : Generation of electrophile SO₃.
2H₂SO₄ ⇌ SO₃ + H₃O⁺ + HSO₄^–

Step 2 : The electrophile SO₃ attacks tihe benzene ring to form a carbocation

Step 3 : Loss of a proton to form a sulphonate ion. The proton is removed by HSO₄^–

Step 4 : Addition of proton to give benzene sulphonic acid.

(ii)Write the resonance hybrid structured of Benzene.
Answer:

b. How is Ethane prepared from sodium acetate by electrolytic method ? 2+1+2
Answer:

Karnataka 1st PUC Chemistry Model Question Paper 1 with Answers

Time: 3.15 Hours
Max Marks: 70

Instruction:

1. The questions paper has five parts A, B, C, D and E. All parts are compulsory.
2. Write balanced chemical equations and draw labeled diagram wherever allowed.
3. Use log tables and simple calculations f necessary (use of scientific calculations is not allowed).

Part – A

Note : Answer any nine questions: ( 9 × 1 = 9 )

Question 1.
Define Molarity of a solution.
Answer:
Number of moles of solute in one litre of the solution.

Question 2.
Name the element having highest value for its Electron gain enthiaply.
Answer:
Chlorine

Question 3.
On what parameter do the Elements are classified in the modern periodic table?
Answer:
Atomic number

Question 4.
What type of Van der waals force exists between HCI molecules?
Answer:
Dipole – dipole interaction

Question 5.
What is the relationship between ∆H and ∆U for the reaction PCl_5(g) ⇌ PCl_3(g) + Cl_2(g) ?
Answer:
∆H = ∆U + RT

Question 6.
The value of Ionic Product of water at 298 K is 1 × 10^-14, what is its [H⁺] ?
Answer:
1 × 10^-7 or 10^-7 Mole/dm³

Question 7.
Name any two gases responsible for Green house effect.
Answer:
Any two gases (CH₄, CO₂, NO₂ etc.)

Question 8.
What is the role of Heavy water in a nuclear reactor?
Answer:
As a moderator Or To slow down fast moving neutrons.

Question 9.
What is Catenation?
Answer:
The tendency of Carbon atoms to link with one another through covalent bonds to form chains and rings.

Question 10.
What type of structural isomerism is shown by the pair : But-1-yne and But-2-yn?
Answer:
Position isomerism.

Question 11.
Which one of the following acids is not present in Acid rain?
Answer:
H – COOH

Part – B

Note : Answer any Five questions: ( 5 × 2 = 10 )

Question 12.
Express i) 5 litre of milk in cubic meter (m³) ii) 25° C in Kelvin.   ( 1 + 1 )
Answer:
i) 5  10^-3 m^-3 …………1   ii) 298 K ………..1

Question 13.
Which of the following species are Isoelectronic with Ne ?  ( 2 )
(Atomic no. of Ne = 10). N^3-,Na⁺,Al³⁺,Ar,Rb⁺ & F^–
Answer:
All elements contains total 10 electrons.

Question 14.
Mention the type of Hydrogen bond in the following compounds.  ( 1 + 1 )
i) Water ii) ortho-Nitrophenol
Answer:
i) Inter molecular hydrogen bonding …………1
ii) Intra molecular hydrogen bonding ………..1

Question 15.
Write Vander Walls equation for one mole of a gas and name any two terms in it.   ( 1 + 1 )
Answer:

Question 16.
Calculate the pH of a solution whose Hydrogen ion conc. is 1.5 × 10³ M.    ( 2 )
Answer:
pH = – log[H⁺]
pH = – log(1.5 × 10^-3)
pH = 3 – log 1.5 = 3 – 0.1761
pH = 2.8239

Question 17.
What is the composition of Permutit (Zeolite) ? How does it works in softening of hard water?  ( 1 + 1 )
Answer:
Hydrated sodium aluminium silicate / Sodium aluminium silicate ………..(1) It exchanges Mg²⁺ and Ca²⁺ ions for its Na⁺ hence soften the hard water …. (1)

Question 18.
Explain the action of heat on Orthoboric acid. Give example.  ( 1 + 1 )
Answer:
When hydro basic acid is heated two moles of water is liberated as follows.

Part – C

Note : Answer any Four questions:  ( 4 × 4 = 16 )

Question 19.
Mention one significance for each of the four quantum numbers.   ( 4 )
Answer:
n = size of the atom
l = orientation, shape
m = subduell (s, p, d, f)
s = Spin of electrons

Question 20.
Write the Electronic configuration, Energy level diagram for the molecular orbitals of Oxygen molecule (O₂). Calculate its bond order and give reason as to why O₂ is paramagnetic.    ( 4 )
Answer:

Atomic number of oxygen = 8. Electronic configuration of oxygen = 1s²2s²2p⁴. When two oxygen atoms combines, the molecular orbital energy level diagram is as shown in the figure.
From the diagram, the molecular electronic configuration of oxygen is

Magnetic property: There are two unpaired electrons {\(\pi_{2 \mathrm{p}_{\mathrm{x}}^{1}}^{*}=\pi_{2 \mathrm{p}_{\mathrm{y}}^{1}}^{*}\)} therefore, oxygen molecule is a paramagnetic in nature.

Question 21.
Calculate the heat of reaction of the following reaction :
C₆H₁₂O_6(s) + 6O_2(g) → 6CO_2(g) + 6H₂O_(g) ; ΔH = ?
C_(graphite) + O_2(g) → CO_2(g);  ΔH = -395.0 kJ … (1)
H_2(g) + \(\frac{1}{2}\)O(g) → H₂O(l); ΔH = -269.5 kJ … (2)
6C_(graphite) + 6H_2(g) + O_2(g) → C₆H₁₂O₆; ΔH = -1169.8 kJ … (3)
Answer:
Multiplying equation (1) and (2) each by 6 reversing (3), we get,
6C_(graphite) + 6O_2(g) → 6CO_2(g); ΔH = -2370 kJ …(4)
6H_2(g) + 3O_2(g) → 6H₂O(l); ΔH = -1616.4 kJ … (5)
C₆H₁₂O_6(s) → 6C_(graphite) + 3O_{2(g) ;} ΔH = +1169.8 kJ …..(6)

Adding (4), (5) and (6),
C₆H₁₂O_6(s) +6O_2(g) → 6CO_2(g) +6H₂O_(g) ;
ΔHg (C₆H₁₂O₆) = -2370.0 – 1616.4 + 1169.8 = -2816.6 kJ

Question 22.
A buffer solution of pH 8.3 is prepared from ammonium chloride and ammonium hydroxide. Dissociation constant of ammonium hydroxide is 1.8 × 10^-5. What is the mole proportion of ammonium chloride and ammonium hydroxide?
Answer:
pOH= 14 – pH =14 – 8.3 = 5.7

Question 23
a. A coulourless liquid ‘A’ contains H and O elements only. It decomposes slowly on exposure to light. It is stabilized by mixing urea to store in the presence of light, (i) Suggest possible structure of A. (ii) Write chemical equations for its decomposition reaction in light.   ( 2 + 2 )
Answer:
The liquid A is hydrogen peroxide (H₂O₂)

b. Give three uses of different allotropic forms of carbon.
Answer:

Forms of carbon	Uses
Diamond	Gemstone, cutting, drilling, grinding, polishing, industry.
Graphite	Reducing agent, refractories, pencils, high temperature, crucibles, electrode making, moderator in nuclear reactors, high strength composite materials.
Activated carbon	Rubber industry, pigments in ink, paints and plastics
Coke	Fuel, strut manufacture
Charcoal	Fuel, reducing agent, Adsorption.

Question 24
a. Explain the mechanism of Halogenation or chlorination of benzene.   ( 3 + 1 )
Answer:
Halogenation: Benzene reacts with chlorine in the presence of FeCl₃ or AlCl₃ to form chlorobenzene.

Machanism : This involves the following steps.
Step 1: Generation of electrohile Cl + Cl – Cl + FeCl₃ → Cl⁺+ FeCl₄^–
Step 2 : The electrophile Cl+ attacks benzene ring to form a carbon cation which is resonance stabilised.

Step 3: Loss of a proton to give chiorobenzene. The proton is removed by FeCl₄.

b. Name the product obtained when Benzene is hydrogenated in presence of heated Nickel catalyst.
Answer:
Cyclohexane  (1)

Part – D

Note : Answer any Four questions: ( 4 × 5 = 20 )

Question 25
a. i) What is the mass percentage of Carbon in Methane ( CH₄ ) (Molecular mass of CH₄ =16)
Answer:
\(\frac{12}{16}\) × 100 = 75% or 75% …….. (1)

ii) Expess 9.8 g H₂SO₄ in mole (Molecular mass of H₂SO₄ = 98)
Answer:
9.8 g H₂SO₄ = 0.1 mole or 0.1 mole …. (1)

iii) What mass of Calcium carbonate is to be decomposed to obtain 4.4 of CO₂ in the following reaction
CaCO₃ → CaO + CO₂ (Molecular mass of CaCO₃ = 100)
Answer:
100 × \(\frac{4.4}{44}\) = 10g or g …… (1)

b. State Avegadro’s law.
How many atoms of Hydrogen are present in 1 mole of water?
Answer:
Under the same temperature & pressure equal volume of gases contains equal number of molecules.
= 2 × 6.022 × 1023 atoms …….. (1)

Question 26
a. The average kinetic energy of a gas molecule at O °C is 5.621 × 10^-27 J. Calculate Boltzmann constant. Also calculate the number of molecules present in one mole of the gas.
Answer:
Average kinetic energy KE = \(\frac{3}{2}\)KT

No. of molecules in 1 mole of the gas (Avagadro’s no.) = \(\frac{R}{k}\)

b. How vapour pressure of liquid is related to (i) temperature, (ii) nature of liquid, (iii) boiling point, (iv) atmospheric pressure?
Answer:
(i) Vapour pressure is directly proportional to temperature.
(ii) If intermolecular force of attraction is less in the liquid, its vapour pressure will be high.
(iii) Higher the vapour pressure, lower will be boiling point.
(iv) If atmospheric pressure is low, boiling point will be less and higher will be the vapour pressure.

Question 27
a. What happens to the solubility of BaSO₄ when a few drops of BaCl₂ solution is added to its saturated solution ? Give reason.
Answer:
Solubility decreases, Due to common ion effect

b. What is meant by Conjugate acid-base pair ?
Write the conjugate acids for CN^– & H₂O.
Answer:
Acid base pair which differ by one photon.
Conjugate acid of CN^– is HCN ; Conjugate acid of H₂O is H₃O⁺

c. An aqueous solution of NH₄Cl is acidic. Give reason.
Answer:
Due to hydrolysis produce HCl, reaction

Question 28
a. Give reason for diagonal relationship of lithium with magnesium.
Answer:
Both Lithium and magnesium have small size and high charge density. The electronegativities of Li is 1.0 and Mg is 1.2. They are low and almost same. Their ionic radii are similar. Hence they show similarities which is known as diagonal relationship between first element of a group with the second element in the next higher group.

b. What is the effect of heat on the following compounds ?
(a) Magnesium chloride hexahydrate
(b) Gypsum
(c) Magnesium sulphate heptahydrate
Answer:

c. Between LiCl and NaCl, LiCl is soluble in Ethanol but NaCl does not give reason.
Answer:
Because LiCl is covalent compound hence dissolves in organic solvent (Ethanol) but NaCl is ionic compound hence insoluble in ethanol.

Question 29
a. How is the estimation of halogens by Carius method ?   ( 4 )

b. Which method is employed for the estimation of carbon and hydrogen organic compounds ?
Answer:
Liebig’s method.

Question 30
a. What is Wurtz reaction ? Give example.   ( 2 )
Answer:
When alkyl halides are heated with sodium metal in ether medium higher alkanes are formed. This reaction is known as Wurtz reaction and employed for the synthesis of higher alkanes containing even number of carbon atoms.

b. How is Methane prepared from sodium acetate ?  ( 2 )
Answer:
Decarboxylation : When sodium salt of carboxylic acid is heated with soda lime (mixture of sodium hydroxide and calcium oxide), an alkane containing one carbon atom less them parent carboxylic acid is formed. This reaction is called decarboxylation.

c. What is the compostion of Zeigler Natta Catalyst?  ( 1 )
Answer:
Triethyl aluminium and titanium tetrachloride inert solvent.

Part – E

Answer any Three of the following questions:  ( 3 × 5 = 15 )

Question 31
a. Draw the structure of d-orbital (Orbital whose Azimuthal quantum no = 2).
Answer:
d – orbital has 5 orientations.

b. What is Isobars ?
Answer:
Atoms of different elements having the same mass number but different atomic numbers are called isobars.

Question 32
a. Define hybridization ? Explain the hybridization in Methane molecule.
(Refer Q. No. 41)
Answer:
CH₄ – Methane Molecule.
The Molecular formula of Methane is CH₄
Electronic configuration of C is ground state – Is² 2s² 2p²
Elecronic configuration of C in excited state – Is² 2s¹ 2p³
Valance orbital representation –

The valence orbital contains unpaired electron. Hence sp³ hybridized carbon combine with 4 hydrogen atom forms methane molecule.

b. What type of orbital over lapping results in the formation of a n-bond ?
Answer:
P-P parallel / sideway / lateral overlapping.

c. Between H₂S & H₂O, H₂O) is more polar. Why ?     3 + 1 + 1
Answer:
Because Oxygen is more electronegative than sulphur.

Question 33
a. Explain the steps involved in Born Haber cycle for the formation of NaCl.
Answer:
Step 1 : Sublimation of metallic sodium of gaseous sodium atom with enthalpy of sublimation = ∆H_s.

Step – 2 : Dissociation of molecule of chlorine to chlorine atoms with enthalpy of dissociation = ∆H_d

Step – 3 : Ionization of gaseous sodium with enthalpy of ionization = ∆H_i

Step – 4 : Addition of electron to gaseous chlorine atom with enthalpy of electron affinity = ∆H_Ea

Step – 5 : Close packing of gaseous sodium ion and chloride’ ion to form lattice structure of NaCl, with lattice chloride ion to form lattice structure of NaCl, with Lattice energy = U ;
NaCl⁺_(g) + Cl^–_(g) → NaCl∆; ∆H = U

Step – 6 : But sum of all the energies will be equal to the heat of formation of one mole of sodium chloride form its reluctant i.e., ∆Hf
Na_(s) + 1/2 Cl_2(g) → NaCl_(s); ∆H = ∆Hf

b. Define the term Entropy. What happens to Entropy when ice melts to liquid water ?  ( 3 + 2 )
Answer:
It is disorderness of the system. Entropy increases.

Question 34
a. Balance MnO₂ + HCl → MnCl₂ + Cl₂ + H₂O
Answer:
Step – 1:
Assign oxidation number :

Step – 2:
Write the oxidation number changes.
Change in oxidation number of Mn + 4 to + 2 = 2
Change in oxidation number of Cl – 1 to 0 = +1

Step – 3: Cross multiply the numbers. Co-efficient 2 is multiplied to HCl and 1 is multiplied to MnO₂.
MnO₂ + 2HCl → MnCl₂ + H₂O + Cl₂

Step – 4: Check the oxidation number, and 2 molecules of HCl on left hand side to balance the chlorine atoms of MnCl₂. In order to balance oxygen and hydrogen atom 2 molecule of H₂O has to be added on the right hand side.
MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂

b. Calculate the oxidation number of the element underline in each of the following cases, (a) Al in Al₂O₃ (b) P in P₂O₅
Answer:
The rule used here is that the algebraic sum of the oxidation numbers of all the atoms a molecule is zero.

Question 35
a. Describe with a neat diagram the estimation of carbon and hydrogen by Leibig’s method.
Answer:
Principle : A known mass of an organic compound is strongly heated with dry cupric oxide (CuO), when carbon and hydrogen are quantitatively oxidized to CO₂ and H₂O respectively. The masses of CO₂ and H₂O thus formed are determined. From this, the percentages of carbon and hydrogen can be calculated.

Procedure : Pure and dry oxygen is passed through the entire assembly of the apparatus (Fig) till the CO₂ and moisture is completely removed.
sample in platinum boat

A boat containing weighed organic substances is introduced inside from one end of the combustion tube by opening it for a while. The tube is now strongly heated till the whole of the organic compound is burnt up. The flow of oxygen is continued to drive CO₂ and water vapours completely to the U-tubes. The apparatus is cooled and the U-tubes are weighed separately.

Observed and Calculations.

1. Mass of organic compound taken = w.g.
2. Mass of water produced = x g (Increase in mass of CaCk tube)
3. Mass of carbon dioxide produced = y g. (Increase in mass of KOH tube)

To determine % of carbon :
Molar mass of CO₂ = 44g mol^-1
Now, 44g of CO₂ = contains 12 g of C.
∴ y g of CO₂ will contain of \(\frac{12 y}{44}\)g of C.
This amount of carbon was present in w. g. of the substance
∴ % C = \(\frac{12 y}{44} \times \frac{100}{w}\)
To determine % of Hydrogen
Molar mass of water = 18 g mol^-1
Now, 18g of H₂O contains 2 g of H₂
∴ x g of H₂O will contain \(\frac{2 x}{18} g\) of H₂
This amount of hydrogen was present in weight of substance.
∴ % H₂ = \(\frac{2 x}{18} \times \frac{100}{w}\)

b. Write the functional grop for i) Aldehyde ii) Ketone.     ( 4 + 1 )
Answer:
i) Aldehyde : (-CHO)
ii) Ketone : (- CO -)

Karnataka 1st PUC Chemistry Model Question Paper 2 with Answers

Time: 3.15 Hours
Max Marks: 70

Instruction:

1. The questions paper has five parts A, B, C, D and E. All parts are compulsory.
2. Write balanced chemical equations and draw labeled diagram wherever allowed.
3. Use log tables and simple calculations f necessary (use of scientific calculations is not allowed).

Part – A

Note : Answer any nine questions: ( 9 × 1 = 9 )

Question 1.
Write the value of Avagadro’s number.
Answer:
6.023 × 10²³

Question 2.
Name the fundamental particles in an atom.
Answer:
Electron, Proton, Neutrons.

Question 3.
Write the general electronic configuration of transition elements.
Answer:
(Noble Gas) (n – 1)d^1–10 ns^1–2

Question 4.
State Law of Conservation of Energy of mass.
Answer:
The total mass of the products in a reaction is equal to mass of the reactants ‘or’ the mass neither be created nor be destroyed.

Question5.
When is ∆H=∆u inareaction?
Answer:
H_2(g) + I_2(g) ⇌ 2HI_g

Question 6.
Define solubility product of weak electrolyte.
Answer:
Solubility product of weak electrolyte is defined as the product of molar concentration of ions of electrolyte raised to appropriate power within saturated solution of that electrolyte.

Question 7.
What is the valency of hydrogen in hydride ion?
Answer:
– 1

Question 8.
Name the isotope of hydrogen which used In nuclear reactor.
Answer:
\(_{1}^{2} \mathrm{H}\) (deuterium)

Question 9.
Name any four alkali metals.
Answer:
Lithium, Sodium, Potassium and Rubedium.

Question 10.
What is the self linking property of an atom known as?
Answer:
Catenation.

Question 11.
Write the IUPAC name of

Answer:
2 Methyl 2 Butene.

Part – B

Note : Answer any Five questions:  ( 5 × 2 = 10 )

Question 12.
Calculate the wave number and wavelength of the first spectral line of Lyman series of hydrogen spectrum.
Rydberg constant R = 10.97 x 106 m^–1
Answer:

8.2275 × 10⁶ m^–1 Wave number v̄ = 8.2275 × 10⁶ m^–1
Wavelength λ = \(\frac{1}{8.2275 \times 10^{6}}\)m = 121.5 × 10^–9 m = 121.5 nm

Question 13.
What is electro negativity? How does it change in a period as well as in a group?
Answer:
The ability of an atom to attract the shared electron pair (of a covalent bond) in a molecule towards itself is called electro negativity. In a period from left to right the electro negativity increases. Down a group electro negativity value decreases.

Question 14.
Mention any two characteristics of ionic compounds.
Answer:

1. They have high Melting point.
2. Many of it are solid in nature.
3. Does not conduct in solid state but good conductors in fused or aqueous state.
4. Soluble in polar solvent & insoluble in non-polar solvent.
5. Ionic bond is non-directional.
6. They do not exhibit Isomerism.

Question 15.
Write the acidity and calculate equivalent weight of following base.
a) Ca(OH)₂ b) Fe(OH)₃
Answer:

Question 16.
Among NH₃, H₂O and HF, which would you except to have highest magnitude of hydrogen bonding and why ?
Answer:
HF, because Flourine is more electronegative.

Question 17.
Calculate the [OH^–] of a solution whose pH is 9.62.
Answer:
pH + pOH = 14 pOH = 14 – pH = 14 – 9.62 = 4.38
pOH = 4.38 = – log₁₀ [OH^– ]; 4.38 = – log₁₀ [OH^– ]
log₁₀[ OH^– ] = – 4.38 ; [OH^–] = antilog (–4.38) = antilog (5 – 4.38 – 5)
= antilog (0.62 – 5) = antilog (0.62) × 10^–5 = 4.169 × 10^–5 mol dm^–3.

Question 18.
Name the oxides of nitrogen. What are the sources ?
Answer:
Nitrogen monoxide (NO), Nitrogen dioxide (NO₂), Dinitrogen trioxide (N₂O₃),
Dinitrogen tetroxide (N₂O₄), Dinitrogen pentoxide (N₂O₅)
The source of oxides of nitrogen are combustion of fossil fuel, especially, petroleum. They are also formed by reaction of N₂ and O₂ in presence of lightening.

Part – C

Note : Answer any Four questions:  ( 4 × 4 = 16 )

Question 19.
4g of copper chloride on analysis was founded to contain 1.890 g of copper (Cu) and 2.110 g of chlorine (Cl). What is the empirical formula of copper chloride? [At. mass of Cu = 63.5 u, Cl = 35.5 u].
Answer:

Empirical formula = CuCl₂.

Question 20.
Based on VSEPR theory explain the structure of water.
Answer:
Electronic configuration of O: Is² 2s² 2p⁴Valence orbited representation :

1. When 2s² orbital hybridised with 2p_x, 2p_y and 2p_z forms the following sp³ hybridisation structure.
2. In 2s² and 2p_x ² the electrons are paired up hence they are not involved in bond formation called loan paired of electron (L.P.)
3. When sp³ hybridised O combines with 2 hydrogen atom forms Bond structure water.

Question 21.
State and illustrate Hess’s law.
Answer:
Hess’s law : Whether a chemical reaction takes place in a single step or in several steps, the total change in enthalpy remains the same.
Consider the formation of CO₂ from C.

Question 22
a. Define oxidation and reduction according to electronic concept.
Answer:
Oxidation is a process in which loss of electrons take place. Reduction is a process in which gain of electrons takes place.

b. Define cathode and anode.
Answer:
Cathode is electrode towards which cations are attracted. Anode is electrode which attracts anions.

Question 23
a. Give the IUPAC name of the following compounds.

Answer:
(i) Propyle Benzene
(ii) 3 Chloro Propenal

b. In Leibig’s method. 0.24 g of organic compound on combustion with dry oxygen produced of 0.62 g of CO₂ and 0.11 g of H₂O. Determine the percentage composition of the compound.
Answer:
Mass of organic compound = m = 0.24 g
Mass of carbon dioxide formed = 0.62 g
Mass of water formed = 0.11 g
Percentage of carbon = \(\frac{12}{4} \times \frac{0.62}{0.24} \times 100\) = 70.45
Percentage of hydrogen = \(\frac{2}{4} \times \frac{0.11}{0.24} \times 100\) = 5.09
Percentage of oxygen = [100 – (70.5 + 5.0)] = 24.46

Question 24
a. Why does benzene undergo electrophilic substitution easily and nucleophilic substitution with difficulty?
Answer:
Because of de-localisation of 671 electrons in the benzene ring.

b. Write the balanced chemical equations for the combination of the following hydrocarbons 2.
(i) Butane (ii) Toulene
Answer:
(i) C₄H₁₀ + \(\frac{3}{2}\)O₂ → 5H₂O + 4CO₂

(ii) C₆H₅CH₃ + 9O₂ → 7CO₂ + 4H₂O

Part – D

Note : Answer any Four questions:  ( 2 × 5 = 10 )

Question 25
a. Summarize the Bohr’s Model of an atom.
Answer:
Bohr’s Model of an atom, the postulates are

1. Electrons revolve around the nucleus of an atom in a certain definite path called Orbit or stationary state of shell.
2. The shells are having different energy levels denoted as K, L, M, N
3. As long as the electron remains in an orbit, they neither absorb nor emit energy.
4. The electron can move only in that orbit in which angular momentum is quantized, i.e., the angular momentum of the electron is an integral multiple of \(\frac{\mathrm{h}}{2 \pi}\).

b. Mention the Merits of Bohr’s theory.
Answer:

1. Explains the formation of hydrogen spectrums
2. It explains the stability of atom
3. Ryd berg constant is calculated by it.

Question 26
a. Explain the structure of CH₄ on the basis of VSEPR theory.

b. Define electronegativity.
Answer:
The ability of an atom to attract the shred electron pair (of a covalent bond) in a molecule towards itself is called electro negativity. In a period from left to right the electronegativity increases. Down a group electronegativity value decreases.

Question 27
a. State First law of thermodynamics and write its mathematical form.
Answer:
The first law of thermodynamics states that the change in internal energy of a system equals the net heat transfer into the system minus the net work done by the system. In equation form, the first law of thermodynamics is ΔU = Q − W.

b. 1 m³ of C₃H₄ at STP is burnt in oxygen, according to the thermochemical reaction : C₂H₄(g) + 3O₂(g) → 2CO₂(g) + 2H₂O(l); ΔH = – 1410 kJ mol^–1 Assuming 70% efficiency, determine how much of useful heat is evolved in the reaction.
Answer:
22.4 L of C₂H₄ at STP produces 1410 kJ of energy.
1000 L of C₂H₄ at STP produces \(\frac{1410}{22.4}\) × 1000 (efficiency)

Question 28
a. Explain Arrhenius concept of acids and bases with example.
Answer:
An electrolyte which when dissolved in water, produces H ion is called acid.
An electrolyte which when dissolved in water, produces OH^– ion is called base.

b. Explain the buffer of acidic buffer.
Answer:
Consider acidic buffer mixture,
CH₃COOH ⇌ CH₃COO^– + H⁺ ; CH₃COONa → CH₃COO^– + Na⁺
Here, acetic acid is a weak electrolyte, in it’s solution there exists equilibrium between it’s ions and molecules. Where as sodium acetate completely dissociates into it’s ions.

Therefore, the buffer mixture contains large number of CH₃COO^– ions followed by Na⁺, H⁺, CH₃COOH.
Case i) When an acid added to this solution :
H⁺ ion of the acid combines with CH₃COO^– ion in buffer solution and makes equillibrium with acetic acid.
CH₃COO^– + H⁺ ⇌ CH₃COOH
As a result pH remains constant.

Case ii) When a base is added to this solution :
OH^– ion of the base combines with H⁺ ion in buffer solution forms water molecule.
H⁺+ OH^– → H₂O.
As a result pH remains constant.

b. The pOH of a solution is 5.725. Calculate the [H⁺].
Answer:
pH + pOH = 14   pH = 14 – pOH = 14 – 5.725 = 8.275
pH = –log₁₀ [H⁺]  ⇒ 8.275 = log₁₀ [H⁺] ⇒
[H⁺] = antilog (- 8.275) = antilog(9 – 8.275 – 9).
[H⁺] = antilog (0.275 – 9) = 5.309 × 10^-9 mol dm^-3.

Question 29
a. Describe an experiment to determine the percentage of nitrogen in an organic compound by Kjeldahl’s method.
Answer:
Principle : When a nitrogenous organic compound is heated with cone. H₂SO₄ using (CUSO₄K₂SO₄) as a catalyst, the nitrogen from the compound is quantitatively converted to ammonium sulphate.

This ammonium sulphate is decomposed by heating with excess of alkali and the ammonia evolved is absorbed in known excess of a standard solution of H₂SO₄. Part of acid is neutralized by ammonia. The excess of acid left behind after neutralization with ammonia is estimated by back titration with standard alkali. From this, the amount of acid actually consumed by ammonia can be obtained which can be used to determine the percentage of nitrogen in the compound.

Procedure : A known exact mass of organic compound (about 0.5g) ix mixed with 10g K₂SO₄, Ig CuSO₄ and 25 ml of conc. H₂SO₄. The mixture is heated strongly in a Kjeldahl’s flask. Till the contents become clear. This step is known as digestion.

The Kjeldahl’s flask is now cooled and the liquid is heated in a round-bottomed flask with excess of caustic soda solution The ammonia evolved is absorbed in a known volume of a standard acid.

The amount of unreacted acid is determined by titrating it against a standard alkali. (NH₄ )₂ SO₄ + 2NaOH → 2NH₃ ↑+Na₂SO₄ + 2H₂O

Observation :

• Mass of organic compound taken = Weight
• Normality of standard acid = N
• Volume of standard acid taken = V₁ ml
• Volume of alkali (Normality = N) required for back titration = V₂ ml

Calculation: Volume of acid used up by ammonia = Volume of ammonia produced = (V₂ – V₁) = V ml of normality N.
Now,
1000 ml of 1 normal NH₃ = 17g NH₃ = 14g N₂
∴ V ml of N – normal ammonia will contain \(\frac{14 \times \mathrm{N} \times \mathrm{V}}{1000}\)gN₂
This amount of nitrogen was present in w g of the compound
∴ %N₂ = \(\frac{14 \times N \times V}{1000} \times \frac{100}{w}\) or %N₂ = \(\frac{1.4 \mathrm{NV}}{\mathrm{w}}\)
Where, N and V are the normality and volume respectively of the acid used up by ammonia.

b. What are isomorphous salts ? Give two examples.
Answer:
Isomorphous salts are those which have same crystalline structure , e.g., MgSO₄, 7H₂O and ZnSO₄, 7H₂O are isomorphous.

Question 30
a. Discuss the molecular orbital theory of benzene.
Answer:
The electronic configuration of carbon in the ground state is
                                                         ’
In the excited state of carbon, one of the 2s electrons gets promoted to 2p orbital. So the electronic configuration of carbon in the excited state is

• All the six carbon atoms in benzene undergoes sp² hybridization to form three sp² hybrid orbitals.
• Each carbon atom in benzene possesses an unhybridised p-orbital containing one electron. They overlap sideways forming three π bonds. The π electrons are delocalised.
• Benzene is a planar molecule with a π electron cloud above and below the ring as shown in above structure. The bond angles are 120°.
• Bond length is 0.139 nm and dipole moment is zero.
• It has twelve a bonds and three π bonds.
• Two carbon atoms to form two sigma bonds and one hydrogen atom to form another sigma bonds.

Part – E

Answer any Three of the following questions:  ( 3 × 5 = 15 )

Question 31
a. Calculate the mass of hydrochloric acid in 200 cm³ of 0.2 N solution of it.
What volume of this acid solution will react exactly with 25 cm³ of 0.14 N solution of sodium hydroxide?
Answer:
Normality of hydrochloric acid = 0.2;
Eq. mass of hydrochloric acid = 36.5
Mass of hydrochloric acid in one dm³ of the solution is given by
W = N × E = 0.2 × 36.5 g
∴ mass of hydrochloric acid in 200 cm3 of the solution = \(\frac{0.2 \times 36.5}{5}\) = 1.46 g

Substituting we have V₁ × 0.2 = 25 × 0.14
∴V₁ = \(\frac{25 \times 0.14}{0.2}\) = 17.5 cm³

b. Write the difference between isotope & isobars.
Answer:

Isotopes	Isobars
Different atoms of the same elements having same atomic number but different mass number are called Isotopes. Ex: 1H1 (Protium), 1H2 (Deuterium), 1H3 (Tritium) 17Cl35 , 17CS37	Element having different atomic number but same mass number are called Isobars. 18Ar40 , 19K40 , 20Ca40

Question 32
a. 50 ml of oxygen were collected at 10° C under 750 mm pressure. Calculate volume at STP.
Answer:
V₁ = 50 ml    V = ?
P₁ = 750 mm   P₂ = 760 mm
T₁ = 10 + 273=283K   T₂ = 273.15K

b. Give any two differences between ideal and real gas.
Answer:

Ideal Gas	Real Gas
1. Obeys ideal gas equation PV = nRT	1. Does not obey the ideal gas equation but obeys Van der walls equation.
2. Ideal gas does not exist in nature.	2. All gases which exist in nature are real gases.

Question 33
a. A buffer solution of pH 8.3 is prepared from ammonium chloride and ammonium hydroxide. Dissociation constant of ammonium hydroxide is 1.8 × 10⁵. What is the mole proportion of ammonium chloride and ammonium hydroxide?
Answer:
pOH= 14 – pH = 14 – 8.3 = 5.7

b. Write the conjugate acid for the following.
(i) C₂H₅NH₂ (ii) CH₃COO^–
Answer:
(i) C₆H₅NH₃⁺ (ii) CH₃COOH

Question 34
a. Describe in brief the manufacture of caustic soda using the Castner-Kellner cell.
Answer:
The Castner-Kellner cell consists of large rectangular trough divided into three compartments with partition short of reaching the bottom of the tank Thus mercury in one compartment can flow into another but solution cannot mix. Graphite anodes are used in outer compartments filled with NaCl solution. The middle compartment contains very dilute solution of caustic soda and filled with iron rods as cathode.

On passing electric current Cl₂ is liberated in outer compartments and sodium liberated at cathode. Mercury forms amalgam which is passed into middle compartment in which mercury acts as anode (having induced +ve potential).
At anode Na⁺ + e^– → Na
At cathode Na + Hg → Na – Hg
2 (Na – Hg) + 2H₂O  → 2NaOH + Hg + H₂
The concentration of NaOH goes on increasing in the middle compartment. When the concentration of NaOH reaches 20% the solution is replaced by dilute solution.

b. Give reason for diagonal relationship of lithium with magnesium.
Answer:
Both Lithium and magnesium have small size and high charge density. The electro negativities of Li is 1.0 and Mg is 1.2. They are low and almost same. Their ionic radii are similar. Hence they show similarities which is known as diagonal relationship between first element of a group with the second element in the next higher group.

Question 35
a. Describe the following in brief:
(i) Ozone depletion over Antarctica (do not write reaction)
(ii) BOD and COD
(iii) Eutrophication
Answer:

(i) Ozone depletion over Antarctica : In summer season, nitrogen dioxide and methane react with chlorine monoxide preventing ozone depletion whereas in winter, special type of clouds called polar stratosphereic could s are formed over Antartica. These clouds provide surface on which chlorine nitrate molecules formed gets hydrolysed to form HOCl. It also reacts with HCls to give Cl₂. When sunlight returns to Antarctica again ozone depletion starts by free radicals.

(ii) BOD : It is amount of oxygen required by bacteria to decompose organize wastes present in water.

COD : It is the amount of oxygen (in ppm) required to oxidize the contaminants. COD is determined by using chemical oxidizing agent K₂Cr₂O₇.

(iii) Eutrophication : The process in which nutrient enriched water bodies support a dense plant polulation which kills animal life by depriving it of oxygen and results in subsequent loss of biodiversity is known as Eutrophication.

b. Distinguish between photochemical smog and classical smog.
Answer:

Photochemical smog	Classical smog
1. It is formed by oxides of nitrogen, hydrocarbons, etc.,	1. It is formed by oxides of sulphur, carbon and particulate matter from combustion.
2. It is oxidizing in nature.	2. It is reducing in nature.
3. Photochemical smog occurs in cities having large number of vehicles. It is not harmful.	3. It occurs in both urban and rural areas. It is harmful.

Karnataka 1st PUC Chemistry Model Question Paper 3 with Answers

Time: 3.15 Hours
Max Marks: 70

Instructions:

1. The questions paper has four parts A, B, C and D.
2. In part A each question carries ONE Marks. In part B, each question carries TWO marks, in part C each question carries FIVE marks. In Part D-1 carries TEN Marks and each question in D-2 carries FIVE marks
3. Write balanced chemical equations and draw diagram wherever necessary.

Part – A

I. Answer of all the following questions: (1 × 9 = 9)

Question 1.
State “Law of definite proportions”.
Answer:
The given compound always contains exactly the same proportion of elements by weight.

Question 2.
Name the fundamental particle of an atom that has highest value for its e/m
Answer:
Electron.

Question 3.
Write the two resonance (canonical/contributing) structures of Ozone.
Answer:

Question 4.
A molecule XY₄ has four bond pairs and 2 lone pairs of electrons for its central atom. Predict the shape of the molecule.
Answer:

Question 5.
How many valence electrons are present around phosphorous in PCls?
Answer:
P – 15 = 1s² 2s² 2p⁶ / 3s² 3p³.

Question 6.
What is the change in internal energy of a system, if 10J of heat is supplied to it and 15J of work is done by it?
Answer:
Since it is a closed system.
∆u = q – w
∆u = 10J – 15J   ∆u= -5J

Question 7.
H^– is a Lewis base. Give reason.
Answer:
H^– can donate a pair of electron. Hence it is a lewis base.

Question 8.
What is the composition of water gas ?
Answer:
CO(g) + H₂(g) or a mixture of carbon monoxide and dihydrogen gas is called as water gas.

Question 9.
Which alkali metal is the strongest reducing agent ?
Answer:
Lithium of Li.

Question 10.
Draw the staggered conformation of Ethane.
Answer:

Question 11.
Mention one use of Chromatography.
Answer:
Chromatography is used to:

• Separate mixtures into their components
• purify components
• test the purity of compounds

Part – B

II. Answer any Five questions: ( 5 × 2 = 10 )

Question 12.
(i) How many significant figures are in 0.2500 g?
(ii) If the mass of one molecule of water is 18 amu, what is the mass of one mole of water molecules ?
Answer:
(i) Four
(ii) 18g.

Question 13.
(i) How does the atomic radius very down a group in the periodic table ?
(ii) Arrange the following in the decreasing order of their ionic radius : N^-3, Mg⁺², Na⁺¹, O^-2
Answer:
(i) Atomic radii increases down a group in the periodic table.
(ii) N^-3 > O^-2 > Na⁺ > Mg²⁺

Question 14.
Among N, Cu, Rn and U, identify the element that: (i) belongs to d-block, (ii) is an actionid
Answer:
(i) Cu,
(ii) U

Question 15.
(i) State Charles’ Law.
Answer:
Charle’s law states that volume of fixed mass of gas is directly proportional to absolute temperature at constant pressure.
\(\left(\frac{\mathrm{V}_{1}}{\mathrm{T}_{1}}=\frac{\mathrm{V}_{2}}{\mathrm{T}_{2}}\right)_{\mathrm{P}}\)

(ii) Give the relationship between molecular mass and density of a gas.
Answer:
(ii) d = \(\frac{P M}{R T}\)

Question 16.
What happens when (i) Sodium hydride is treated with water ?
(ii) Hydrogen peroxide is treated with lead sulphide ?
Answer:
(i) Sodium hydride when treated with water liberate dihydrogen gas
NaH(s) + H₂O(I) → NaOH(l) + H₂(g)

(ii) Hydrogen peroxide on reacting with lead sulphide produces lead sulphate.
4H₂O₂ + PbS → PbSO₄ + 4H₂O

Question 17.
What is the repeating unit in Organo silicon polymer? Name the starting (raw) material used in the manufacture of Organo silicon polymer.
Answer:
R₂ SiO. The starting material is alyl or aryl substituted silicon chlorides.

Question 18.
How is Ozone layer formed in the stratosphere? Name a chief chemical that causes its depletion.
Answer:
In stratosphere the free oxygen atoms combine with the molecular oxygen is presence of UV radiations to form ozone.

The chemical that causes its depletion is chlorofluorocarbon compounds or CFCs or fireons.

Part – C

I. Answer any Four questions: (4  × 4 = 16)

Question 19.
(i) State Heisenberg’s uncertainty principle. Give its mathematical equation.
Answer:
It is impossible to determine both the momentum (particle nature) and position (wave nature) of a moving sub atomic particle simultaneously with absolute accuracy.
Mathematically ∆x × ∆p = h / 4π where ∆x = uncertainty in position:
∆p = uncertainty in momentum ; h = Plank’s constant = 6.626 × 1O^-34 Js.

(ii) Calculate the wave number of the spectral line of shortest wave length appearing in Given, R = 1.09 × 107 m1
Answer:
\(\overline{\mathbf{v}}=\mathrm{R}\left(\frac{1}{\mathrm{n}_{1}^{2}}-\frac{1}{\mathrm{n}_{2}^{2}}\right) \mathrm{m}^{-1}\)
v̄ = 1.09 × 10⁷ m^-1 \(\left(\frac{1}{2^{2}}-\frac{1}{0}\right)\)
v̄ = 1.09 × 10⁷ (\(\frac{1}{4}\))
v̄ = 0.2725 × 10⁷   v̄ = 2.725 × 10⁶ m^-1

Question 20.
(i) Mention two conditions for the linear combination of atomic orbitals.
(ii) Write the electronic configuration of C₂ molecular. What is its magnetic property ?
Answer:
(i) (a) The combining atomic orbitals must have the same or nearly the same energy
(b) The combining atomic orbitals must have the same symmetry about the molecular axis.
(c) The combining atomic orbitals must overlap to the maximum extent.
It is diamagnetic. E.C. of C₂ molecule is \(\sigma 1 \mathrm{s}^{2} \sigma^{*} 1 \mathrm{s}^{2} \sigma 2 \mathrm{s}^{2} \sigma^{*} 2 \mathrm{s}^{2} \pi 2 \mathrm{px}^{2}=\pi 2 \mathrm{py}^{2}\)

Question 21.
(i) Define “Standard Enthalpy of Vapourisation”
(ii) Write thermo chemical equation for vaporization of Ethanol (C₂H₃OH)
(iii) Calculate the enthalpy of vapourisation of ethanol, given enthalpies of formation of liquid Ethanol and gaseous Ethanol as -277.6 kJ and -235.4kJ respectively.
Answer:
(i) Amount of heat required to vaporize one mole of a liquid at constant temperature under standard pressure (1 bar) is called standard enthalpy of vaporization.
(ii) C₂H₃OH(l) → C₂H₃OH(g) ; ∆H = +QkJ
(iii) ΔH_vap= Hp-Hr .
ΔH_vap =-235.4kJ-(-277.6kJ)
ΔH_vap = 42.2kJ

Question 22.
(a) For
(i) What is the oxidation number of Oxygen in (2) ?
(ii) What type of Redox reaction is it?
(b) Balance the Redox reaction using oxidation number method.
SO₂ + H₂S → S + H₂O
Answer:
(i) -2
(ii) Disproportionation or Disproportionate reaction.

(b)

Multiply oxidation equation by 2 and reduction equation by 1.
SO₂ → S
2H₂S → 2S
Add both the equations
SO₂ + 2H₂S → 3S
Balancing the atoms of hydrogen and oxygen by introducing suitable number of H₂O molecules to the product.

Question 23.
(a) How is sulphur detected using the ‘Sodium fusion extract’ of the given organic compound ?
(b) Give the IUPAC name of

Write the bond line diagrame of 2-methyl pentane.
Answer:
(a) Te sodium fusion extract is acidified with acetic acid and lead acetate. A black precipitate of lead sulphite is formed which indicates the presence of sulphur.

(b) Cyclohexanol

Question 24.
(a) Give equation for each of the following reactions.
(i) Water is dropped on Calcium carbide
(ii) Hydrogen bromide is added to propene in presence of peroxide
(iii) Phenol is heated with Zinc dust.
(iv) Benzene is treated with Chlorine in presence of Ferric chloride.
Answer:
(a) (i) CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂

(b) (i) Write the equation for the steps involved in the mechanism of nitration of Benzene between Toluene and Nitrobenzene which one is more reactive towards Nitration ?
Answer:
Nitration benzene reacts with a mixture of concentrated nitric acid and concentrated sulphuric acid at 50°C to form nitrobenzene.

Mechanism: This involves the following steps
Step 1: Generation of electrophile nitronium ion NO₂⁺
HNO₃ + 2H₂SO₄ → NO₂⁺ + H₃O⁺+ 2HSO₄^–

Step 2: The electrophile NO₂⁺ attacks the benzene ring to form a carbocation which is resonance stabilized.

Step 3: Loss of proton to give nitrobenzene. The proton is removed by HSO₄^–

Part – D

Answer any Four questions: ( 4 × 5 = 20 )

Question 25
a. Calculate the mas of Magnesium required to completely react with 250 cm³ of O.1 M HCl.
Given : Mg + 2HCl – MgCl₂ + H₂    Atomic mass of Mg = 24
Or (Internal choice)
100cm³ of a solution of HCl completely neutralizes 25cm³ of 0.1 M NaOH.
Calculate the mass of HCl present in 100cm³.
(b) Mention two postulates of ‘Dalton’s atomic theory’.
Answer:
(a) 250 × 0.1 M = 25 millimoles of HCl
From the equation it is clear that 2HCl is reacting with one Mg.
∴ 25 millimoles of HCl rect with 12.5 millimoles of Mg
∴ Mass of magnesium required = volume of Mg × atomic weight = 12.5 × lO^-3 × 24 = 0.3 g of Mg.
OR
(a) V_Hcl = 100cm³, V_NaOH = 25cm³, MHCl = ?, M_NaOH = 0.1M
aHcl V_Hcl × M_Hcl = V_NaOH × M_NaOH × aNaOH
here aHCl = basicity of HCl = 1, aNaOH = acidity of NaOH = 1
M_Hcl = \(\frac{25 \times 0.1}{100}\) = 0.025m
Mass of HCl present in 100cm³

b. Mention two postulates of ‘Dalton’s Atomic theory’
Answer:
The postulates of Dalton’s atomic theory are :

1. The matter consists of indivisible atoms.
2. All the atoms of a given elements have identical properties including identical mass. Atoms of different element differ in mass.
3. Compounds are formed when atoms of different elements combine in a fixed ratio.
   OR (Internal choice)

What is Empirical formula ? Give an example for a compound whose Empirical formula and molecular formula are the same
Answer:
Emperical formula represents the simplest whole number ratio of various atoms present in a compound.
Example : C₂H₈.

Question 26.
(a) Define the terms:
(i) Bond order
(ii) Bond length
(iii) Bond enthalpy
Answer:
(i) It is the number of covalent bonds holding the atoms in the molecule.
Example: If the bond is formed by the sharing of two electron pairs, then the bond order is 2. O=O or C = C bond in alkenes.
(ii) Bond length: It is the equilibrium distance between nuclei of two bonded atoms in a molecule.
(iii) Bond enthalpy: It is the amount of energy required to break one mole of bonds of a particular type between two atoms in a gaseous state.

b. With respect to the formation of Ethane molecule mention.
(i) hybridation of Carbon. (ii) number of sigma bonds in the molecule.
Answer:
(i) sp²
(ii) 5

Question 27.
(a) Write three postulates of ‘Kinetic theory of gases’.
Answer:

1. Gases are made up of large number of the minute particles.
2. Pressure is exerted by a gas
3. There is no loss of kinetic energy.
4. Molecules of gas attract on one another.
5. Kinetic energy of the molecule in directly proportional to absolute temperature.
6. Actual volume of the gaseous molecule very small.
7. Gaseous molecules are at always in motion.
8. There is more influence of gravity on movement of gaseous molecule.

(b) Two gases A & B have critical temperatures as 250 and 125 K respectively. Which one of these can be liquefied easily and why ?
Answer:
Gas a can be easily liquefied. Because higher critical temperature, greater is the inter molecular force of attraction.

Question 28.
(a) Calculate the pOH of a solution obtained when 0.05 mol NH₄Cl is added and dissolved in 0.025M ammonia solution. Kb for ammonia is 1.77 × 10^-5
(b) For the equilibrium : BaCO₃(s) ⇌ BaO(s) + CO₂(g)
(i) Write the expression of Kp.
(ii) What is the effect of ‘increase in pressure’ on the above equilibrium ?
Answer:
(a) pK_b = – log[Kb]
= – log [1.77 × 10^-3]
= 5 – 0.2480 = 4.752

pOH= 4.752 + log2 = 4.752+ 0.3010 = 5.053

(b) (i) K_p = P_CO2
(ii) Increase in pressure shifts the equilibrium to left or backward reaction is favoured.

Question 29.
(a) Give reason (i) Coodination number of Be is 4, but that of Mg is six
(ii) Lithium iodide is covalent but potassium iodide is ionic.
Answer:
(a) (i) Beryllium does not have ‘d’ subshell in n = 2 level. It has only 4 valence orbital.
Hence it can have a coordination number 4.
Mg has ‘d’ subshells in n = 3 level. Hence it has more valence orbital. Therefore it can have a coordination number 6.

(ii) Lithium iodide is covalent because of the smaller atomic size of lithium atom, it distorts to the electron to the electron cloud of iodine towards it. Or K has less polarizing power than Li⁺.

(b) Compared the 2^nd Ionisation enthalpies and Hydration enthalpies of Alkali and Alkaline earth metals/ions.
Answer:
Alkali metals have higher value of 2^nd ionization enthalpy than alkaline earth metals.
since they achieve a stable noble gas configuration after loosing 1 electron from ns¹ shell.

Alkaline earth metal ions have higher value of hydration enthalpy because of their smaller ionic size than alkali metals.

(c) What is the chemical formula of plaster of paris ?
Answer:
CaSO₄. 1/2H₂O

Question 30
(a) Name the method by which Halogen present in an organic compound is estimated ? O.1 g of an organic compound gives 0.08g of silver bromide, Calculate the percentage of bromine.
Atomic masses : Ag = 108, Br = 80
(b) What is inductive effect ?
Which one of the following shows maximum hyper conjugation effect ?
CH₃CH = CH₂, (CH₃)₂ = C = CH₂        CH₂ = CH₂
Answer:
(a) Carius method

molecular mass of AgBr = 108 + 80 = 188
Mass of silver bromide = 0.09g
Mass of organic compound = O.1 g
% of bromine = \(\frac{80 \times 0.08 \times 100}{188 \times 0.1}\) = 34.04%

(b) The percentage displacement of bonded sigma electrons along the chain of carbon atoms due to the presence of a substitutent group of different electro negativity is called inductive effect.
(CH₃)₂ C = CH₂

Part – E

Answer any three questions: (3 × 5 = 15)

Question 31.
(a) For the Element with atomic number 24:
(i) Write the electron configuration
(ii) Write the value of u & 1 for its electron in the valence shel.
(ii) How many unpaired electrons are present in it ?
Answer:
(a) (i) 1s² 2s² 2p⁶ 3s² 3p⁶, 4s¹ 3d⁵
(b) n = 4, l = 0
(c) Six or 6.

(b) What is photo electric effect ? Does the effect support particle nature or wave nature of light ?
Answer:
The effect in which the electrons gets ejected when certain metals are exposed to a beam of light is called as photo electric effect.
It supports the particle nature of light.

Question 32.
(a) What is a spontaneous process ?
For the equilibrium A + 2B ⇌ C
∆H is + 400 kJ and ∆S is + 200 JK^-1
Calculate the temperature above which the reaction becomes spontaneous ?
Answer:
The process that takes place on its won without the assistance of external agency is called spontaneous process.
∆G = ∆H – T∆S
At equilibrium, ∆G = 0
T∆S = ∆H

T = 2000 K.

(b) For Cl₂ → 2Cl Assign the sigans for ∆G and ∆S.
Answer:
∆H = +ve (endothermic reaction)
∆S = -ve (entropy increases)

Question 33.
(a) Calculate the solubility of Ag₂CrO₄4 in 0.1M AgNO₃K_sp of Ag₂ CrO₄ = 1 × 10^-12
Ans:

K_sp = [Ag⁺]² [CrO₄^2- ]
1 × 10^-12 = (2 x 0.1)² [CrO₄^2- ]

b. An aqueous solution of sodium acetate has pH greater than 7.
Explain with equation.
Answer:
Sodium acetate is a salt of a strong base and a weak acid which undergoes hydrolysis to form strong alkaline (basic) solution. Hence the pH is greater than 7.
CH₃COONa + H₂O ⇌ CH₃COOH + NaOH

Question 34.
(a) Give reasons :
(i) The stability of +3 oxidation state of 13 group elements decreases down the group.
(ii) Boron is used as control rods in nuclear reactors.
(iii) Graphite is soft and slippery.
Answer:
(a) (i) The stability of +3 oxidation state of group 13 elements decreases down the group due to the inert pair effect on ns2 electrons. This is because of the poor shielding effect of electron in ‘d’ and ‘f’ orbitals.
(ii) Because it absorbs neutrons
(iii) Due to the weak vander waal’s force of attraction between the layers of hexagonal rings.

b. Complete the following equation :
(i) 2Al + 2 NaOH + → 6H₂O
(ii)
Answer:
(i) 2Al + 2NaOH + 6H₂O → 2Na + [Al(OH)₄ ] + 3H₂
(ii)

Question 35.
(a) Give two tests to distinguish between alkanes and alkenes.
(b) Naphthalene is an aromatic compound justify the statement using Huckle rule.
(c) Draw cis and trans structures of CHBr = CHBr
Answer:
(a) (i) Test with bromine water or CCl₄
Alkenes react with bromine water of CCl₄ to form dibromo alkane, Where as alkanes do not show such rection.
(ii) Test with alkaline. KMnO₄ or Baeyer’s reagent test:
Alkenes react with Baeyer’s reagent to produce glycol, Where as alkenes do not show such reaction.

(b) According to Hucle rule, if naphthalein is an aromic compound it should possess (4n + 2) π electrons delocalized in the ring.
In naphthalein, n = 2
Number of delocalized p electrons = (4n + 2) = 4 × 2 + 2
= 10π electrons
Hence naphthalein is an aromatic compound.

(c)

Karnataka 1st PUC Chemistry Model Question Paper 4 with Answers

Time: 3.15 Hours
Max Marks: 70

Instructions:

1. The questions paper has four parts A, B, C and D.
2. In part A each question carries ONE Marks. In part B, each question carries TWO marks, in part C each question carries FIVE marks. In Part D-1 carries TEN Marks and each question in D-2 carries FIVE marks
3. Write balanced chemical equations and draw diagram wherever necessary.

Part – A

I. Answer of all the following questions: (1 × 9 = 9)

Question 1.
What is the S.I. Unit of density ?
Answer:
Kg/m² or kgm^-3

Question 2.
How do isotopes of an element differ from one another ?
Answer:
Atoms having same atomic number but different atomic masses.
OR
Isotopes of an element differ only in the number of protons.

Question 3.
What are representative elements ?
Answer:
Elements of s-block and p-block are representative elements.

Question 4.
Between CO & CO₂, which diffuses faster ?
Answer:
CO diffuses faster.

Question 5.
Give a chemical reaction for which ∆H = ∆U.
Answer:
2H_(g) ⇌ H_2(g) + I_2(g)

Question 6.
Give the relation between K_p and K_c for the equilibrium N₂(g) + 3H₂(g) ↔ 2NH₃(g).
Answer:
K_p = K_c = (RT)²

Question 7.
What is the chemical used in Clarke’s process to remove temporary hardness of water ?
Answer:
Lime or Ca(OH)₂ or Calcium hydroxide.

Question 8.
Write the General outer electronic configuration of s-block elements.
Answer:
General electronic configuration of s-block elements is ns^1-2

Question 9.
Complete the following equation 2Fe⁺² + 2H⁺ + H₂O₂ → ……. + H₂O
Answer:
2Fe⁺²+ 2H⁺ + H₂O₂ → 2Fe⁺³+ 2H₂O

Question 10.
Suggest a suitable method to separate sugar and salt from an aqueous solution containing them.
Answer:
Fractional crystallization is a suitable method to separate sugar and salt from an aqueous solution containing them due to difference in their solubilities in water.

Question 11.
Trans-2 Butene has higher melting point than cis-2-butene, why ?
Answer:
Because more close packing of molecules is possible in trans-isomer due to more symmetry.

Part – B

II. Answer any Five questions: (5 × 2 = 10)

Question 12.
Name the quantum number that specifies
(i) Size of an orbital
(ii) Shape of an orbital.
Answer:
(i) Principal quantum number specifies size of an orbital
(ii) Azimuthal quantum number specifies shape of an orbital.

Question 13.
(i) Distinguish between Sigma and Pi bonds.
Answer:

Sigma (σ) Bond	Pi (π) Bond
1. The bond is formed by the axial overlap of the atomic orbitais.	1. The bond is formed by the sidewise overlap of the atomic orbitais.
2. s-orbitais can take part in the sigma bond formation	2. s-orbitais do not take part in the pi-bond formation.

Question 14.
Give the reasons for the deviation of real gases from ideal behaviour ?
Answer:

1. There is no intermolecular force of attraction within gaseous molecules (at high pressure and low temperature there is appreciable intermolecular force of attraction).
2. The actual volume of the molecule is negligible as compared to total volume of the gas. (At high pressure the gaseous molecule occupy minimum volume, which is not negligible).

Note: Because of this deviation Vander waal modified the ideal gas pressure and ideal gas volume respectively.

Question 15.
Why do group 1 metals have lower first ionisation Enthalpy than corresponding group 2 metals.
Answer:

1. Size of 1^st group metals is greater than size of 2^nd group metals, hence effective nuclear charge increase of 2^nd group metal.
2. Upon losing one electron, 1^st group metals attain stable octet structure.

Question 16.
Justify the position of Hydrogen in the periodic table.
Answer:
Hydrogen has been placed at the top of the alkali metal family.
Hydrogen and alkali metals resemble in the following aspects.

1. Electronic configuration : Hydrogen has one electron in its valance shell like the alkali metals H – 1s¹.
2. Electropositive character : As both hydrogen and alkali metals form monovalent cations by losing the electron in the valance shell. H → H⁺ + e^–

Question 17.
What happens when formic acid is heated with Cone. H₂SO₄? Give the equation.
Answer:
Dehydration takes place or CO is formed

Question 18.
What is meant by Biochemical Oxygen Demand (BOD)? What is its significants?
Answer:
The amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water is called Biochemical Oxygen Demand (BOD) The amount of BOD in the water is a measure of the amount of organic material in the water, in terms of how much oxygen will be required to break it down biologically.

Part – C

I. Answer any Four questions: (4 × 4 = 16)

Question 19.
A compound contains 4.07% hydrogen, 24.27% Carbon and 71.65% Chlorine. Its molar mass is 98.96. Calculate is Empirical and Molecular formulae.
Answer:

Empirical formula = CH₂Cl
Molecular formula = n × Empirical formula

Molecular formula = 2 × CH₂Cl = C₂H₄Cl₂.

Question 20.
(a) Explain the formation of methane molecule on the basis of hybridization.
Answer:
The electronic configuration of the central carbon atom (z = 6) in methane is 2, 4. Each of the four electrons present in the valence shell forms shared pairs with the electrons of the hydrogen atoms as shown below :

Methane has a tetrahedral structure which is multiplanar, in which carbon atom lies at the centre and the four hydrogen atoms lie at the four comers of regular tetrahedran. All H – C – H bond angles are 109.5°

(b) Between O₂ & O₂^–  , which one has higher bond order ?
Answer:
O₂ has higher bond order than O₂^–

Question 21.
(a) What is Oxidation Number ? What is the oxidation Number of Cl is KClO₃?
Answer:
Oxidation number is the oxidation state of an element in a compound ascertained according to a set of rules formulated on the basis that the electrons in a co-valent bond belong entirely to the more electro negative elements.
Oxidation number of Cl in KClO₃ is +5.

(b) Write separate equations for the oxidation and reduction reactions occurring in the following redox reaction.
2Fe + 2HCl → FeCl₂ + H₂
Answer:
2Fe + 2HCl → FeCl₂ + H₂
Fe → Fe²⁺ +2e^–
2H⁺ + 2e^– → H₂

Question 22.
(a) What are Isothermal and Adiabatic process ?
Answer:
Isotherman process : A process is said to be isothermal in case the temperature of the system remains fixed or constant i.e., operation is carried at constant temperature.

Adiabatic process : In an adiabatic process, no exchange of heat between the system and the surroundings is possible i.e., the system is completely isolated or insulated from the surroundings.

(b) State the II law of Thermodynamics. Give the equation that relates Gibbs energy with Entropy and Enthalpy of a system ?
Answer:
Second law of thermodynamics can be stated in a number of forms:

• All spontaneous processes or naturally occurring processes are thermo dynamically irreversible.
• Without the help of an external agency, a spontaneous process cannot to reversed.
• The entropy of an isolated system increase if it is to be spontaneous in a particular direction.
• In a non-isolated system, the total entropy of both the system and surroundings must increase or must be positive.
• The total entropy of the universe must tend to increase in a spontaneous process.
  G = H – TS

Question 23.
(a) Giving justification, catogorise the following species as Nuclophile or Electrophile.
(i)SO₃, (ii) C₂H₅O
Answer:
(i) SO₃ – Electoplite, because it is an electron deficient and accepts a pair of electrons.
(ii) C₂H₂O – Nucleophile because it is an electron rich and donates electrons.

OR (Internal Choice)

Mention the differences between Fractional distillation and Steam Distillation.
Answer:

Fractional distillation	Steam distillation
1. Liquid. and impurities must process different boiling points.	1. Liquid must be steam voilatile impurities present must be no volatice.
2. Liquid may or may not be mixable with water	2. Liquid must not mixable with water.

(b) Write the IUPAC names of the following compounds.
Answer:

OR (Internal Choice)

Explain position isomerism with suitable example.
Answer:
The isomers differ with respect to the position of the multiple bonds, substituents or functional groups
Ex .

Question 24.
(a) Give equations for the reaction that occurs when
(i) Ehyene is treated with Baeyer’s reagent.
(ii) Enthyene is treated with sodium metal in the ratio I : 2.
Answer:

(b) Explain Friedel – Craft’s acylation with an example.
Answer:
Friedel-Craft’s acylation : Reaction between benzene and acetyl chloride in presence of anhydrous AlCl₃, is called Friedel-craft’s acylation.

Part – D

Answer any Four questions: (4 × 5 = 20)

Question 25.
(a) Write any three postulates of Bohr’s atomic model.
Answer:
Bohr’s Model of an atom, the postulates are

1. Electrons revolve around the nucleus of an atom in a certain definite path called Orbit or stationary state of shell.
2. The shells are having different energy levels denoted as K, L, M, N, ……
3. As long as the electron remains in an orbit, they neither absorb nor emit energy.
4. The electron can move only in that orbit in which angular momentum is quantized, i.e., the angular momentum of the electron is an integral multiple of \(\frac{\mathrm{h}}{2 \pi}\).

b. Calculate the energy with 5th orbit of hydrogen atom.
Answer:

Question 26.
Define enthalpy of formation.
Calculate Enthalpy of formation of C₂H_6(g) given the enthalpy of combustion of C₂H_4(g) C₂H_6(g) and H_2(g) as – 140 kJ/mol, -1550 kJ/mol and -286 kJ/mol respectively.
Answer:
(a) Heat of formation of a compound is the change in enthalpy produced when one mole of the compound is formed from its elements denoted as ∆H_f.

(b) C₂H_4(g) + CO_2(g) → 2CO_3(g) + 2H₂O_(g)           ∆_cH° = — 140kJ/mol … (1)
H_2(g) + \(\frac{1}{2}\) O_2(g) → H₂O_(g)                                 ∆_cH° =-286kJ/mol …(2)
C₂H_6(g) + \(\frac{7}{2}\) O_2(g) → 2CO_2(g) + 3H₂O_(g)  ∆_cH° = -1550kJ/mol … (3)
Required equation
C₂H_4(g) + H_2(g) → C₂H_6(g)      ∆_fH° = ?
Reverse equation (3)
2CO_2(g) + 3H₂O_(g) → C₂H_6(g) + \(\frac{7}{2}\) O_2(g)   ∆_cH° = -1550kJ / mol …(4)
Add equation (1), (2) and(4)
H_2(g) + \(\frac{1}{2}\) O_2(g) → H₂O_(g)
C₂H_4(g) + 3O_2(g) → 2CO_2(g) + 2H₂O_(g)
2CO_2(g) + 3H₂O_(g) → C₂H_6(g) + \(\frac{7}{2}\) O_2(g)
C₂H_4(g) + H_2(g) → C₂H_6(g)
∆_fH° = 15550 kJ/mol – 140kJ/mol – 286 kJ/mil
∆_fH° = 1124kJ/mol.

Question 27.
(a) (i) State Le-Chatelier’s principle,
(ii) What is common ion effect. Give an example.
Answer:
(i) Definition : “when a constraint applied to a system at equilibrium in a reversible reaction, the equilibrium shifts so as to nullify the constraint”.
[Constraint is change in temperature or pressure, addition of reactant or product]

(ii) Supression in degree of dissociation of a weak electrolyte by addition of a common ion is called common ion effect.
Example: CH₃COOH and CH₃COONa

OR (Internal Choice)

(i) What is the pH of 1M NaCl at 298K.
(ii) What happens to the pH of a solution of Acetic acid when some sodium acetate is dissolved in it? Explain
Answer:
(i) pH = 7
(ii) pH of the acid solution increases
(iii) Because of common ion effect dissociation of acetic acid decreased and hence [H⁺] decreases.

(b) Acetic acid has a dissociation constant of 1.8 × 10^-5, Calculate the pH value of the decinormal solution of Acetic acid.
Answer:

pH = -log[H⁺] = -log 01.34 × 10^-1 = 2.872

OR (Internal Choice)

Calculate the ionization constant of 0.05M weak acid if it’s degree of dissociation is 0.018.
Answer:
\(\mathrm{K}_{\mathrm{a}}=\frac{\alpha^{2}}{\mathrm{C}}=\frac{(0.018)^{2}}{0.05}=6.48 \times 10^{-3}\)

Question 28.
(a) Describe LCAO method for the formation molecular orbitals of Hydrogen. Write the energy level diagram for these orbitals.
Answer:
The formation of bonding molecular orbital when two atomic orbitals of hydrogen atoms (Is orbital) combine by the addition of their wave functions is shown below.

The atomic orbitals of these atoms may be represented by the wave function TA, TB Mathematically, the formation of molecular orbitals may be described by the linear combination of atomic orbitals that can take place by addition and by substruction of wave functions of individual atomic orbitals as shown below :

Ψ_mo = Ψ_A ± Ψ_B
Therefore, the two molecular orbitals σ and are σ’ formed as
σ = Ψ_A = ’Ψ_B
σ’ = Ψ_A = Ψ_B
The MO σ formed by the addition of atomic orbitals is called the bonding molecular orbital while the molecular orbital σ’ formed by the substraction of atomic orbital is known as antibonding molecular orbitals.

(b) Give two difference Bonding and Antibonding molecular orbitals.
Answer:

Bonding molecular orbital	Antibonding molecular orbital
1. A bonding molecular orbital is formed by the linear combination of two atomic orbitals when their wave functions are added.	1. An antibonding molecular orbital formed by the linear combination of two atomic orbitals when their wave functions are added.
2. It is formed when the lobes of the combining atomic orbitals have same sign	2. It is formed when the lobes of the combining atomic orbitals have opposite signs.

Question 29.
(a) What is the formulae of inorganic benzene ? Write the structure of Diborane and explain the nature of bonding in it.
Answer:
Formulae of inorganic benzene is B₃N₃H₆.
Structure of Diborane

Bonding in diborane : Each B atom uses sp3 hybrides for bonding. Out of the four sp3 hybrids one each B atom, one is without electrons shown in shaded region. The terminal B – H bonds are normal 2 – centre – 2 electron bonds but the two bridge bonds are 3 – centre – 2 – electron bridge bonds are also referred to as balance bonds.

(b) What are Fullurenes ? How are they prepared ?
Answer:
Carbon exhibits many allotropic forms: both crystallins as well as amorphous. Diamond and graphite are two well known crystalline forms of carbon, third form of corbon known as fullerences.

Fullerenes are made by heating of graphite in an electric are in the presence of inert gases such as helium or argon. The sooty material formed by condensation of vapourised Ca small molecular consists of-mainly C60 with smaller quantity of C70 and traces of fallerences consiting of even number of carbon atoms upto 350 or above.

Question 30 a.
(a) Writ the principles involved in the estimation of (i) Halogens (ii) Sulphur present in an organic compound.
Answer:
(i) Halogens : Halogens reacts with silver nitrate to for precipitate of silver halides.
X + Ag⁺ → AgX .
X represents a halogen -Cl, -Br or -1

(ii) Sulphur
S⁺+ [Fe(CN)₅NO]² → [Fe(CN)₅NOS]^4-
Sulphur reacts with nitropresside to form a violet colour complex.

(b) Name the element estimated by Kjeldahl’s method.
Answer:
Nitrogen is estimate by Kjeldahl’s method.

Part – E

Answer any Three questions: (3 × 5 = 15)

Question 31.
(a) Calculate the mole fraction of Ehtanol (C₂H₅OH) in the solution containing 20g of Ethanol and 100g of water.
Answer:
Weight of ethanol = 20g
Weight of water = 100g
Molecular mass of C₂H₅ – OH = – 46
No of moles of ethanol = \(\frac{20}{46}\) = 0.4348 moles.
n₈ = No of moles of water = \(\frac{100}{18}\) = 5.555 moles

X_A = 0.07259

(b) How are 2 mole NaOH and 2 Molar NaOH different ?
Answer:
2 mole NaOH
1 mole of NaOH = 40g of NaOH = 6.023 × 10²³ molecules.
2 mole of NaOH 2 × 40g = 80g of NaOH
= 2 × 6.023 × 10²³ molecules.
2 molar NaOH
1 molar NaOH = 40g of NaOH in 1000 ml of water
2 molar NaOH = 80g of NaOH in 100 ml of water
= 2 moles of NaOH dissolved in 1000 ml of its solution.

Question 32.
(a) Sate Gay Lussac’s law.
Calculate the pressure exerted by 4 mole of a gas occupying a volume of 1.5m³ at 100 K. Given R = 8.314 J/k/mol.
Answer:
(i) Gay Lussac’s law (Pressure – temperature relationship)
Gay Lussac’s law states that at constant volume, pressure of a fixed amount of a gas varies directly with the temperature.
(ii) Given n = 4 moles
V = 1.5m³, T = 100k, R = 8.314 J/k/mol,    P = ?

(b) Draw z vs P graph for an Ideal gas, and CO₂ gas
Answer:

Question 33.
(a) What are buffer solutions ? Given an example for an acidic buffer.
Answer:
The solution which resist the pH or pOH when an acid or base is added to it. Buffer solution is a mixture of weak electrolyte and its salt.
A solution containing a weak acid and its salt with a strong base.
(i) CH₃COOH + CH₃COONa
(ii) HCOOH + HCOOK

(b) Calculate the solubility of A2 x 3 pure water, Assuming that neither king of ion reacts with water. The solubility product of A2X3 Ksp = 1.1 × 10^-23 .Explain with equation.
Answer:
k_sp =[A³⁺]² [X^-2]³ = [2s]² [3s]³ =108s⁵
S⁵ = \(\frac{1.1 \times 10^{-23}}{108}\) = 1 × 10^-25
S⁵ = 1 × 10^-5 mol dm^-3

Question 34.
(a) Give equations for the reactions that occur when
(i) Sodium metal is dropped into water
(ii) Magnesium metal is heated in air.
(iii) Sodium peroxide dissolves in water.
Answer:

Hydrogen gas is liberated.

(ii) NO₂ gas is liberated.
2Mg(NO₃)₂ → 2MgO + 4NO₂ + O₂

(iii) H₂O₂ is formed.
Na₂O₂ + 2H₂O → 2NaOH + H₂O₂

b. What happens when limited amount of CO₂ gas is passed into milk of lime ? Give equation.
Answer:
Lime water turns milky or white Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Question 35.
(a) Between -NO₂ and -Br, which one of these is a in eta directing group? Write equation for the conversion of Benzene into p-Bromonitrobenzene.
Answer:
-NO₂ is meta directing group.

(b) State anti Merkovnikoff s rule and explain with an example.
Answer:
In the presence of peroxide, addition of HBr to un symmetrical alkenes like propene takes place contrary to the Merkovnikoff s rule. This happens only with HBr but not with HCl or HI. This reaction is know as peroxide or Kharash effect or anti- Merkovnikoff s rule

Students can Download 1st PUC Chemistry Model Question Paper 3 with Answers, Karnataka 1st PUC Chemistry Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

Karnataka 1st PUC Chemistry Model Question Paper 3 with Answers

Time: 3.15 Hours
Max Marks: 70

Instruction:

1. The questions paper has five parts A, B, C, D and E. All parts are compulsory.
2. Write balanced chemical equations and draw labeled diagram wherever allowed.
3. Use log tables and simple calculations f necessary (use of scientific calculations is not allowed).

Part – A

I. Answer ALL of the following (each question carries one mark): ( 10 × 1 = 10 )

Question 1.
‘Cis platin’ a medicine used in the treatment of which disease?
Answer:
Cancer/Cancer Tumour.

Question 2.
Write the mathematical expression for Boyle’s law.
Answer:
V ∝ \(\frac{1}{P}\) at constant temperature.

Question 3.
Give the example for gaseous reversible reaction for which Kp = Kc
Answer:
H_2(g) + I_2(g) ⇌ 2HI_(g)

Question 4.
Which group elements in the periodic table are called Noble gases?
Answer:
18th group.

Question 5.
What is the oxidation number of the element in its free state?
Answer:
0 or Zero.

Question 6.
Write the general electronic configuration of First group elements.
Answer:
ns¹

Question 7.
Why is boric acid considered as weak acid?
Answer:
Due to small size of B and presence of only six electrons in the valence shell i.e. protonic acid.

Question 8.
Mention the structure of SiO₄^4-.
Ans.
Tetrahedral structure.

Question 9.
Give an example for non-benzenoid compound.
Answer:
Pyridine

Question 10.
Write the expanded form of ‘CNG
Answer:

Part – B

II. Answer any FIVE of the following questions carrying TWO marks ( 5 X 2 = 10 )

Question 11.
Convert 37°C to °F.
Answer:
°F = \(\frac{9}{5}\) + °C +32 = \(\frac{9}{5}\) X 37 + 32 = 98.6°

Question 12.
Under what conditions of temperature and pressure real gases tend to behave ideally?
Answer:
Low pressure and high temperature.

Question 13.
What is dipole moment? What is its SI unit.
Answer:
It is the product of +ve or negative charge and the distance between the centre of them, μ = e x d
SI unit coulomb meter or cm.

Question 14.
Write any two diagonal relationship between Beryllium and Aluminium.
Answer:
(a) Both forms covalent compounds and soluble in organic compounds.
(b) Both BeCl₂ and AlCl₃ act as Lewis acids.

Question 15.
Give the reaction for the synthesis of water gas and producer gas.
Answer:

Question 16.
How is chloromethane converted to methane?
Answer:
Chloromethane heated with zinc and NaOH to methane.

Question 17.
Illustrate Markovnikov’s rule with an example.
Answer:

The Br^– of HBr is added to double bonded carbon as containing less of OH atoms to give 2–bromopropanol.

Question 18.
What is BOD? What is its significance?
Answer:
The amount of oxygen consumed by the microorganisms in decomposing the organic matter present in water is called BOD. It is a water quality parameter to know the amount of organic matter available for bacteria.

Part – C

III. Answer any FIVE of the following questions; carrying THREE marks: ( 5 x 3 = 15 )

Question 19.
(a) Give reason : Ionic radius of F^– is more than atomic radius of F.
Answer:
Due to more number of electrons in F^– than F.

(b) How does ionization enthalpy varies down the group?
Answer:
Ionisation enthalpy decreases down the group due to increase in atomic size of atoms.

(c) Ionization enthalpy of nitrogen is more than that of oxygen. Give reason.
Answer:
Due to completely half filled p-orbitals (1s² 2s² 2p³) in nitrogen but in oxygen atom p-orbital is more than half-filled.

Question 20.
With the help of MOT write the energy level diagram of hydrogen molecule. What is its bond order and predict magnetic property.
Answer:
BO = \(\frac{1}{2}\) (N_BMO N_ABMO)
= \(\frac{1}{2}\)(2 – 0 ) = 1
It is diamagnetic due to absence of unpaired electrons in the molecule.

Question 21.
Calculate the formal charge of each oxygen atom of ozone molecule
Answer:

Question 22.
(a) Give any two differences between sigma and pi bonds.
Answer:
Sigma Bond

1. Head to Head overlapping of AO.
2. It is strong bond due to large overlapping.
3. Free rotation is possible.

Pi Bond

1. Lateral (sideways) overlapping of AO.
2. It is weak bond due to small overlapping.
3. Free rotation about n bond is not possible.

(b) What is the magnetic nature of oxygen molecule?
Answer:
It is paramagnetic due to presence of unpaired electrons in π_px π_py antibonding molecular orbitals.

Question 23.
Balance the following redox reaction using oxidation number method.
MnO₂ + Br^– → Mn²⁺ +Br₂ + H₂O (In Acidic medium)
Answer:

Step II – Oxidation Reaction x 2
Reduction Reaction x 1

Balance the O atoms (add to RHS) and balance the H+ ions (To LHS)
MnO₂ + 2B^– + 4H⁺ → Mn⁺² +2Br₂ +2H₂O

Question 24.
(i) Explain the laboratory preparation of dihydrogen.
Answer:
In the laboratory, dihydrogen is prepared by adding dil. H2S04 to granulated zinc.
i.e. Zn + H₂SO₄ (dil) → ZnSO₄ + H₂
The H₂ gas liberated is collected by downward displacement of water.

(ii) Give an example of ionic hydride.
Answer:
LiH/NaH/CaH₂/BaH₂ etc.

Question 25.
Give any three points of differences between lithium and other alkali metals.
Answer:

1. Small size of lithium and its ion.
2. High charge to size ratio (polarising power).
3. High ionization enthalpy and low electropositive character of lithium.
4. Absence of d-orbitals.

Question 26.
(i) Write the molecular formula of silica.
Answer:
SiO₂

(ii) Write the partial structure of silicone.
Answer:

(iii) Name the catalyst used in gasoline production.
Answer:
ZSM-5.

Part – D

IV. Answer any FIV E of the following questions’carrying FIVE marks: ( 5 x 5 = 25 )

Question 27.
(a) An organic compound contains 69% carbon and 4.8% hydrogen, the remainder being oxygen. Calculate the masses of carbon dioxide and water produced when 0.20 gram of this substance is subjected to complete combustion.
Answer:
Given % carbon = 69%, H = 4.8%, w = 0.20g

(b) Give an example each for element and compound.
Answer:
Element = sodium/Na.
Compound = NaOH/sodium hydroxide.

Question 28.
(a) Write the significance of quantum numbers n, I and m.
Answer:
(i) Principal quantum number (n): Determines energy and size of the orbits (electrons).
(ii) Azimuthal Q.N. (1): Determines the shape of the suborbitals (s,p,d,f).
(iii) Magnetic Q.N. (m): Determines the orientation of the orbitals.

(b) State Pauli’s exclusion principle.
Answer:
For two electrons of an atom the values of n, 1 and m but s is different.
OR
No two electrons of an atom can have the same values of n, 1 and m are same 3 is different.

(c) Write the electronic configuration of copper (Z = 29).
Ans. Cu29= 1s²2s²2p⁶3s²3p⁶3d¹⁰4s¹

Question 29.
(a) The FM station of All India Radio, Hassan, broadcast on a frequency of 1020 kilohertz. Calculate the wavelength of the electromagnetic radiation emitted by the transmitter.
Answer:
Given γ = 1020 kilohertz = 1020 x 1000 hertz
C = 3 x10⁸ ms^-11 λ = ?

(b) What is the maximum number of electrons present in third main energy level?
Answer:
Third Main energy level = M r /.
∴ No. of electrons in M shell = 18e.

Question 30.
(a) Give any three postulates of kinetic molecular theory of gases.
Answer:

1. ll gases are made up of with many number of tiny particles called molecules.
2. Gas molecules are separated from each other by large distance. Hence the volume of the gas molecules is negligible compared to total volume of the gas.
3. There is no force of attraction between the gas molecules.
4. The average kinetic energy of gas molecules is directly proportional to Kelvin temperature.

(b) On a ship sailing in Pacific Ocean where temperature is 23.4°C, a balloon is filled with 2L air. What will be the volume of the balloon when the ship reaches 1 the Indian Ocean where temperature is 26.1°C?
Answer:
V₁= 2L V₂ = ?
T₁= 23.4°C + 273 = 296.4 K
T₂ = 26.1°C + 273K = 299.1K

Question 31.
(a) The combustion of one mole benzene takes place at 298K and 1 atm. After combustion, CO₂(g) and H₂O (l) are produced and 3267.0 kJ of beat is liberated. Calculate the standard enthaipy of formation of benzene.
Given : Standard enthalpy of formation of CO₂(g) and H₂O (1) are – 393.5 kJ mol^-1 and -285.0 kJ mol^-1 respectively.
Answer:
Required equation : 6C (s) + 3H₂(g) → C₆H₆ (l); ∆H_f = ?
(i) C₆H₆(l) + \(\frac{15}{2}\)O₂(g) → 6CO₂(g) + 3H₂O(l); ∆H_c = -3267KJ
(ii) C(s) + O₂(g) → CO₂ (g); ∆H_f = -393.5 KJ
(iii) H₂(s) + \(\frac{1}{2}\)O₂(g) → H₂O(l); ∆H_f= -285 KJ
reverse the equation (i) + (ii) 6 + (iii) * 3

(b) Write the mathematical expression for First law of thermodynamics.
Answer:
∆U = q +w or ∆U = q – P∆V

(c) Give an example of isolated system.
Answer:
Tea placed in a thermos flask.

Question 32.
(a) What are the values for ArH° and ArS° for reaction to be spontaneous at all
temperatures?
Answer:
When ∆_rH° = -ve and ∆_rS° = +ve the process is spontaneous at all temperture.

(b) Write the relationship between
(i) Enthalpy (H) and infernal energy (U) (ii) C_p and C_v.
(iii) Free energy (G) Enthalpy (H) and Entropy (S).
Answer:
(i) ∆H = ∆U + P∆V
(ii) C_p – C_v= R for 1 mole of an ideal gas
C_p – C_v =nR for n moles of an ideal gas
(iii) ∆G = ∆H – T∆S

Question 33.
(a) The following concentrations were obtained for the formation of NH₃ from N₂ and H₂ at equilibrium 500K. [Ni] = 1.5 x 10^-2 M, [H₂] = 3.0 x 10^-2 M and [NHJ = 1.2 x 10^-2 m. Calculate the equilibrium constant.
Answer:
Given [N₂] = 1.5 x 10^-2 M, [H₂] = 3.0 x 10^-2 M and [NH₃] = 1.2 x 10^-2m
For N₂(g) + 3H₂ (g) → 2NH₃ (g)

b) Define common ion effect
Answer:
It is the process of decreasing (or suppression) the dissociation of a weak electrolyte by adding a strong electrolyte having a common ion is called common ion effect.

(c) What is the relationship between [HsO+] and [OH-] for neutral solution?
Answer:
[H₃O₊] = [OH^–].

Question 34.
(a) What is acid and bases according to Arrhenius concept?
Answer:
Arrhenius Acid : Substances which give hydrogen ion in water are called Arrhenius Acid. Example: HCl. HNO₃
Arrhenius base : Substances which gives hydroxyl ion (OH-) in water are called Arrhenius bases.
Example: NaOH, KQH, NH₄OH, etc.

(b) Give an example for (i) so.M-vapoisr equilibrium (ii) liquid-vapour equilibrium,
(i) I₂(s) → I₂ (vapour) / NH₄Cl(s)⇌ NH₄Cl(vapour) (ii) H₂O(l) → H₂O(v).

(c) Write the equilibrium K. expression for H2 + I2
Answer:
K_c = \(\frac{\left[\mathrm{H}_{2}\right]\left[\mathrm{I}_{2}\right]}{[\mathrm{HI}]^{2}}\)

Part – E

V. Answer any TWO of the following questions carrying FIVE marks: ( 2 x 5 = 10 )

Question 35.
(a) For the molecule CH₃CH₂CH₂OH
(i) Identify functional group
Answer:
Functional group = – OH

(ii) Write the bond line forarulbu
Answer:
Bond line formula =

(iii) Write the succeeding homologue.
Succeeding homologue = CH₃CH₂CH₂CH₂OH

(b) Explain inductive effect with a suitable example.
Answer:
The permanent displacement of a (sigma) electrons along the saturated carbon chain away/ towards the group/atom attached at the end of the chain.

Question 36.
(a) An organic compound contains 69% carbon and 4.8% hydrogen, the remainder being oxygen. Calculate the masses of carbon dioxide and water produced when 0.20 g of this substance is subjected to complete combustion.
Answer:
Given % carbon = 69%, H = 4.8%, w = 0.20g

(b) What are nucleophiles? Give an example.
Answer:
Chemical species having -ve charge reacts with nucleus of an atom/molecule is called nucleophile, e.g: H^–, CN^–, H₂O, NH₃, CP^–, Br^– etc.

Question 37.
(a) Explain the mechanism of chlorination of methane.
Answer:
Mechanism of chlorination of methane :
Step I : Chain initiation: Methane and Cl₂ heated in UV light, Cl₂ undergoes homolytic fission giving chlorine free radicals,

Step II: Chain propagation: Cl reacts with methane gives methyl free radical,

Methyl free radical reacts with Cl2 molecule gives C1‘ radical, i.e. CH₃ + Cl₂ → CH₃Cl + Cl’ These are repeated several times.

Step III: Chain termination:
The reaction goes to the end when the free radicals reacts with each other.

(b) Write the Newman’s projections of ethane.
Answer: