Class 11 Physics Chapter 13 Kinetic Theory Solved Questions and Answers

1 Which of the following diagrams (Fig. in below) depicts ideal gas behaviour?

Kinetic Theory

A (a)

B (b)

C (c)

D (d)

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Answer:(a), (c)

2 In a diatomic molecule, the rotational energy at a given temperature

A obeys Maxwell’s distribution.

B have the same value for all molecules.

C equals the translational kinetic energy for each molecule.

D is (2/3)rd the translational kinetic energy for each molecule.

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Answer:A, D

3 Diatomic molecules like hydrogen have energies due to both translational as well as rotational motion. From the equation in kinetic theory pV = (2/3)E, E is

A the total energy per unit volume.

B only the translational part of energy because rotational energy is very small compared to the translational energy.

C only the translational part of the energy because during collisions with the wall pressure relates to change in linear momentum.

D the translational part of the energy because rotational energies of molecules can be of either sign and its average over all the molecules is zero.

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Answer:only the translational part of the energy because during collisions with the wall pressure relates to change in linear momentum.

4 ABCDEFGH is a hollow cube made of an insulator (Fig. in below). Face ABCD has positve charge on it. Inside the cube, we have ionized hydrogen.

The usual kinetic theory expression for pressure

Kinetic Theory

A will be valid.

B will not be valid since the ions would experience forces other than due to collisions with the walls.

C will not be valid since collisions with walls would not be elastic.

D will not be valid because isotropy is lost.

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Answer:B, D

5 1 mole of H₂ gas is contained in a box of volume V = 1.00 m³ at T = 300K. The gas is heated to a temperature of T = 3000K and the gas gets converted to a gas of hydrogen atoms. The final pressure would be (considering all gases to be ideal)

A same as the pressure initially.

B 2 times the pressure initially.

C 10 times the pressure initially.

D 20 times the pressure initially.

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Answer:20 times the pressure initially.

6 A cylinder containing an ideal gas is in vertical position and has a piston of mass M that is able to move up or down without friction (Fig. in below). If the temperature is increased,

Kinetic Theory

A both p and V of the gas will change.

B only p will increase according to Charle’s law.

C V will change but not p.

D p will change but not V.

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Answer:V will change but not p.

7 A cubic vessel (with faces horizontal + vertical) contains an ideal gas at NTP. The vessel is being carried by a rocket which is moving at a speed of 500m s^–1 in vertical direction. The pressure of the gas inside the vessel as observed by us on the ground

A remains the same because 500m s⁻¹ is very much smaller than v_rms of the gas

B remains the same because motion of the vessel as a whole does not affect the relative motion of the gas molecules and the walls.

C will increase by a factor equal to (v²_rms + (500)²) / v²² where v rms was the original mean square velocity of the gas.

D will be different on the top wall and bottom wall of the vessel.

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Answer:remains the same because motion of the vessel as a whole does not affect the relative motion of the gas molecules and the walls.

8 Which of the following properties of gas molecule the one that is same for all ideal gases at a particular temperature is

A Mass

B Velocity

C Momentum

D Kinetic energy

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Answer:Mass

9 One any planet, the presence of atmosphere implies [nrms = root mean square velocity of molecules and ne = escape velocity]

A nrms << ne

B nrms > ne

C nrms = ne

D nrms = 0

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Answer:nrms << ne

10 A unit mass of solid converted to liquid at its melting point. Heat is required for this process is

A Specific heat

B Latent heat of vaporization

C Latent heat of fusion

D External latent heat

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Answer:Latent heat of fusion

11 If 2 kcal, of heat is supplied to a system cause to change the internal energy of a gas is 5030J, and external work done is 3350 J, then what is mechanical equivalent of heat?

A 41.90 J/kcal

B 4190 J/cal

C 4.19 J/kcal

D 4.19 J/cal

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