JEE Physics Kinetic Theory MCQS Set A

Question. Select the appropriate property of an ideal gas
(a) All of these
(b) It strictly obeys the ideal gas laws
(c) There are no forces of interaction between its molecules
(d) Its molecules are infinitesimally small

Answer: A

Question. A real gas behaves as an ideal gas at
(a) Very low pressure and high temperature
(b) High pressure and low temperature
(c) Low pressure and low temperature
(d) High pressure and high temperature

Answer: A

Question. By increasing temperature of a gas by 6°C its pressure increases by 0.4 %, at constant volume. Then initial temperature of gas is
(a) 1500 K
(b) 2000 K
(c) 750 K
(d) 1000 K

Answer: A

Question. Boyle’s law is obeyed by
(a) Ideal gas of constant mass and temperature
(b) Real gas of constant mass and temperature
(c) Both ideal and real gases at constant temperature and variable mass
(d) Both ideal and real gases of constant mass and variable temperature

Answer: A

Question. For an ideal gas the fractional change in its volume per degree rise in temperature at constant pressure is equal to [T is absolute temperature of gas]
(a) T^–1
(b) T²
(c) T³
(d) T⁰

Answer: A

Question. The raise in the temperature of a given mass of an ideal gas at constant pressure and at temperature 27° to double its volume is
(a) 327°C
(b) 54°C
(c) 300°C
(d) 600°C

Answer: A

Question. Which of the following methods will enable the volume of ideal gas to be increased four times?
(a) Double the temperature and reduce the pressure to half
(b) Double the temperature and also double the pressure
(c) Reduce the temperature to half and double the pressure
(d) Reduce the temperature to half and reduce the pressure to half

Answer: A

Question. When pressure remaining constant, at what temperature will the r.m.s. speed of a gas molecules increase by 10% of the r.m.s. speed at NTP?
(a) 57.3ºC
(b) 557.3 K
(c) –57.3ºC
(d) 57.3 K

Answer: A

Question. Select the incorrect statement about Maxwell’s speed distribution
(a) The distribution curve is symmetric about the most probable speed
(b) The area under the distribution curve gives total number of molecules of the gas
(c) The distribution function depends only on the absolute temperature
(d) None of these

Answer: A

Question. An ant is moving on a plane horizontal surface. The number of degrees of freedom of the ant will be
(a) 2
(b) 3
(c) 6
(d) 1

Answer: A

Question. Molar specific heat at constant volume, for a non-linear triatomic gas is (vibration mode neglected)
(a) 3R
(b) 4R
(c) 2R
(d) R

Answer: A

Question. A mixture of ideal gases has 2 moles of He, 4 moles of oxygen and 1 mole of ozone at absolute temperature T. The internal energy of mixture is
(a) 16 RT
(b) 14 RT
(c) 11 RT
(d) 13 RT

Answer: A

Question. 14 g of CO at 27°C is mixed with 16 g of O₂ at 47°C. The temperature of mixture is (vibration mode neglected)
(a) 37°C
(b) 27°C
(c) 32°C
(d) –5°C

Answer: A

Question. On increasing number density for a gas in a vessel, mean free path of a gas
(a) Decreases
(b) Increases
(c) Remains same
(d) Becomes double

Answer: A

Question. At room temperature the rms speed of the molecules of a certain diatomic gas is found to be 1920 m/s. The gas is
(a) H₂
(b) F₂
(c) Cl₂
(d) O₂

Answer: A

Question. Variation of atmospheric pressure, with height from earth is
(a) Exponential
(b) Hyperbolic
(c) Parabolic
(d) Linear

Answer: A

Question. A narrow glass tube, 80 cm long and opens at both ends, is half immersed in mercury, now the top of the tube is closed and is taken out of mercury. A column of mercury 20 cm long remains in the tube. Find atmospheric pressure
(a) 60 cm of Hg column
(b) 20 cm of Hg column
(c) 20 cm of air column
(d) 60 cm of air column

Answer: A

Question. One mole of monatomic gas and three moles of diatomic gas are put together in a container. The molar specific heat (in JK^–1 mol^–1) at constant volume is (Let R = 8 JK^–1 mol^–1)
(a) 18
(b) 19
(c) 20
(d) 21

Answer: A

Question. The temperature of a gas is –68°C. At what temperature will the average kinetic energy of its molecules be twice that of –68°C?
(a) 137°C
(b) 127°C
(c) 100°C
(d) 05°C

Answer: A

Question. An ideal gas is filled in a closed container and container is moving with uniform acceleration in horizontal direction. Neglect gravity. Pressure inside the container is
(a) Less in front
(b) Less at back
(c) Less at top
(d) Uniform everywhere

Answer: A

Question. One kg of a diatomic gas is at pressure of 8 × 10⁴ N/m². The density of the gas is 4 kg/m³. The energy of the gas due to its thermal motion will be
(a) 5 × 10⁴ J
(b) 3 × 10⁴ J
(c) 4 × 10⁴ J
(d) 7 × 10⁴ J

Answer: A