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BITSAT SERIES
Physics

Kinetic Theory

21 previous year questions.

Volume: 21 Ques
Yield: High

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Chapter Questions
21 MCQs

01
PYQ 2007
easy
physics ID: bitsat-2
In the absence of intermolecular forces of attraction, the observed pressure will be
1
P
2
< P
3
> P
4
Zero
02
PYQ 2011
medium
physics ID: bitsat-2
The molecules of a gas have rms velocity 200 m/s at 27°C. Find rms velocity at 127°C if pressure is constant.
1
(400)/(\sqrt3)
2
100\sqrt2
3
(100\sqrt2)/(3)
4
(100)/(3)
03
PYQ 2012
medium
physics ID: bitsat-2
The average translational kinetic energy of (molar mass 32) molecules at a particular temperature is 0.048 eV. The translational kinetic energy of (molar mass 28) molecules in eV at the same temperature is:
1
0.0015 eV
2
0.003 eV
3
0.048 eV
4
0.768 eV
04
PYQ 2012
medium
physics ID: bitsat-2
For a gas if ratio of specific heats at constant pressure and volume is , then value of degrees of freedom is:
1

2

3

4

05
PYQ 2013
medium
physics ID: bitsat-2
The temperature of an ideal gas is increased from 27°C to 127°C, then the percentage increase in is
1
37%
2
11%
3
33%
4
15.5%
06
PYQ 2014
medium
physics ID: bitsat-2
In the kinetic theory of gases, which of these statements is/are true? (i) The pressure of a gas is proportional to the mean speed of the molecules. (ii) The root mean square speed of the molecules is proportional to the pressure. (iii) The rate of diffusion is proportional to the mean speed of molecules. (iv) The mean translational kinetic energy of a gas is proportional to its kelvin temperature.
1
(ii) and (iii) only
2
(i), (ii) and (iv) only
3
(i) and (iii) only
4
(iii) and (iv) only
07
PYQ 2015
easy
physics ID: bitsat-2

mole of an ideal gas at constant temperature is kept inside a cylinder of length and cross-sectional area , closed by a massless piston. The cylinder is attached to a conducting rod of length , cross-sectional area and thermal conductivity , whose other end is maintained at . The piston is moved such that heat flow through the conducting rod is constant. Find the velocity of the piston when it is at a height from the bottom of the cylinder. (Neglect any loss of heat from the system.)


1

2

3

4
08
PYQ 2016
medium
physics ID: bitsat-2
The average kinetic energy of an ideal gas molecule in SI units at 25°C will be:
1

2

3

4
7.16×10⁻20J
09
PYQ 2016
medium
physics ID: bitsat-2
The molecules of a given mass of a gas have an r.m.s. velocity of 200 m s⁻¹ at 27°C and 1.0 × 10⁵ N m⁻² pressure. When the temperature and pressure of the gas are 127°C and 0.05 × 10⁵ N m⁻², respectively, the r.m.s. velocity of its molecules is:
1

2

3

4
(100)/(3)
10
PYQ 2017
medium
physics ID: bitsat-2

One mole of an ideal gas is taken from state A to state B by three different processes,
(i) ACB (ii) ADB (iii) AEB as shown in the P–V diagram. The heat absorbed by the gas is

1
greater in process (ii) than in (i)
2
the least in process (ii)
3
the same in (i) and (iii)
4
less in (iii) than in (ii)
11
PYQ 2017
medium
physics ID: bitsat-2
Five gas molecules chosen at random are found to have speeds of 500, 600, 700, 800 and 900 m/s.
1
The root mean square speed and the average speed are the same.
2
The root mean square speed is 14 m/s higher than the average speed.
3
The root mean square speed is 14 m/s lower than the average speed.
4
The root mean square speed is √(14) m/s higher than the average speed.
12
PYQ 2018
medium
physics ID: bitsat-2

The mass of an H₂ molecule is 3.32×10⁻²⁷ kg. If 10²³ hydrogen molecules per second strike 2 cm² of a wall at an angle of 45° with the normal while moving at a speed of 10⁵ cm/s, the pressure exerted on the wall is nearly:

1

2

3

4
1660N/m²
13
PYQ 2018
medium
physics ID: bitsat-2
The ratio of specific heats of a gas is (Cp)/(Cᵥ) = 1.66. The gas may be:
1

2

3

4
NO₂
14
PYQ 2019
medium
physics ID: bitsat-2

0.5 mole of an ideal gas at a constant temperature of 27°C is kept inside a cylinder of length L and cross-section area A, closed by a massless piston. The cylinder is attached to a conducting rod of length L, cross-section area A/19, and thermal conductivity k, whose other end is maintained at 0°C. The piston is moved such that the rate of heat flow through the rod is constant. The constant velocity of the piston when it is at height L/2 from the bottom is

1

2

3

4
(k)/(1000R)m/s
15
PYQ 2020
medium
physics ID: bitsat-2
The average kinetic energy of an ideal gas molecule in SI unit at 25^∘C will be:
1

2

3

4
7.16×10⁻20J
16
PYQ 2020
medium
physics ID: bitsat-2
The molecules of a given mass of a gas have r.m.s. velocity of 200m s⁻1 at 27^∘C and 1.0×10⁵N m⁻2 pressure. When the temperature and pressure of the gas are respectively 127^∘C and 0.05×10⁵N m⁻2, the r.m.s. velocity of its molecules in m s⁻1 is:
1

2

3

4
(100)/(3)
17
PYQ 2021
medium
physics ID: bitsat-2
Five gas molecules chosen at random are found to have speeds of 500, 600, 700, 800 and 900m/s.
1
the root mean square speed and the average speed are the same.
2
the root mean square speed is 14m/s higher than the average speed.
3
the root mean square speed is 14m/s lower than the average speed.
4
the root mean square speed is √(14)m/s higher than the average speed.
18
PYQ 2022
easy
physics ID: bitsat-2
The de-Broglie wavelength of an electron moving with a velocity (where ) is equal to the wavelength of a photon. The ratio of the kinetic energies of the electron and the photon is:
1

2

3

4

19
PYQ 2023
medium
physics ID: bitsat-2
Mercury kept in the refrigerator has length L. If taken out in atmospheric pressure condition, length remains the same due to?
20
PYQ 2025
medium
physics ID: bitsat-2
In a mixture of gases, the average number of degrees of freedom per molecule is 6. If the rms speed of the molecule is , what is the velocity of sound in the gas?
1

2

3

4
21
PYQ 2026
medium
physics ID: bitsat-2
In a mixture of gases, the average number of degrees of freedom per molecule is 6. The rms speed of the molecule of the gas is , then the velocity of sound in the gas is
1

2

3

4