CBSE Class 11 Physics Kinetic Theory MCQs Set 02

Question: Gases exert pressure on the walls of the container because the gas molecules
a) possess momentum
b) collide with each other
c) have finite volume
d) obey gas laws.
Answer: a

Question: Boyle’s law is applicable for an
a) adiabatic process
b) isothermal process
c) isobaric process
d) isochoric process
Answer: b

Question: According to kinetic theory of gases, which one of the following statement(s) is/are correct?
a) Real gas behave as ideal gas at high temperature and low pressure.
b) Liquid state of ideal gas is impossible
c) At any temerature and pressure, ideal gas obeys Boyle’s law and charles’ law
d) The molecules of real gas do not exert any force on one another.
Answer: a

Question: On a particular day, the relative humidity is 100% and the room temperature is 30ºC, then the dew point is
a) 70ºC
b) 30ºC
d) 100ºC
d) 0ºC
Answer: b

Question: The perfect gas equation for 4 gram of hydrogen gas is
a) PV = RT
b) PV = 2RT
c) PV= 1/2RT
d) PV = 4RT
Answer: b

Question: A fixed mass of gas at constant pressure occupies a volume V. The gas undergoes a rise in temperature so that the root mean square velocity of its molecules is doubled. The new volume will be
a) V/2
b) V / 2
c) 2 V
d) 4 V
Answer: d

Question: If masses of all molecule of a gas are halved and their speed doubled then the ratio of initial and final pressure will be
a) 2 : 1
b) 1 : 2
c) 4 : 1
d) 1 : 4
Answer: b

Question: The molecules of a given mass of gas have a root mean square velocity of 200m s^–1 at 27°C and 1.0 × 105 N m^–2 pressure. When the temperature is 127°C and the pressure 0.5 × 105 Nm^–2, the root mean square velocity in ms^–1, is
a) 400/√3
b) 100√2
c) 100√2/3
d) 100/3
Answer: a

Question: The ratio of principal molar heat capacities of a gas is maximum for
a) a diatomic gas
b) a monatomic gas
c) a polyatomic gas having linear molecules.
d) a polyatomic gas having non-linear molecules.
Answer: b

Question: The kinetic theory of gases
a) explains the behaviour of an ideal gas.
b) describes the motion of a single atom or molecule.
c) relates the temperature of the gas with K.E. of atoms of the gas
d) All of the options
Answer: d

Question: In kinetic theory of gases, it is assumed that molecules
a) have same mass but can have different volume
b) have same volume but mass can be different
c) have different mass as well as volume
d) have same mass but negligible volume.
Answer: d

Question: A sample of an ideal gas occupies a volume of V at a pressure P and absolute temperature. T. The mass of each molecule is m. The equation for density is
a) m k T
b) P/k T
c) P/(k T V)
d) P m/k T
Answer: d

Question: Two gases A and B having the same temperature T, same pressure P and same volume V are mixed. If the mixture is at the same temperature T and occupies a volume V, the pressure of the mixture is
a) 2 P
b) P
c) P/2
d) 4 P
Answer: a

Question: The total degree of freedom of a CO₂ gas molecule is
a) 3
b) 6
c) 5
d) 4
Answer: c

Question: At room temperature, the rms speed of the molecules of a certain diatomic gas is found to be 1930 m/s. The gas is
a) H₂
b) F₂
c) O₂
d) Cl₂
Answer: a

Question: The K.E. of one mole of an ideal gas is E = (3/2) RT. Then Cp will be
a) 0.5 R
b) 0.1 R
c) 1.5 R
d) 2.5 R
Answer: d

Question: The value of critical temperature in terms of van der Waal’s constant a and b is given by
a) T_c = 8a/27Rb
b) T_c = a/27Rb
c) T_c = -a/Rb
Answer: a

Question: If one mole of a monatomic gas (g = 5/3) is mixed with one mole of a diatomic gas (g = 7/3), the value of g for the mixture is
a) 1.40
b) 1.50
c) 1.53
d) 3.07
Answer: c

Question: Let v denote the rms speed of the molecules in an ideal diatomic gas at absolute temperature T.The mass of a molecule is ‘m’ Neglecting vibrational energy terms, the false statement is
a) a molecule can have a speed greater than 2v
b) v is proportional to T
c) the average rotational K.E. of a molecule is 1/4 mv²
d) the average K.E. of a molecule is 5/6mv
Answer: c

Question: The density of a gas is 6 × 10^–2 kg/m³ and the root mean square velocity of the gas molecules is 500 m/s. The pressure exerted by the gas on the walls of the vessel is
a) 5×10³ N/m²
b) 1.2×10^–4 N/m²
c) 0.83×10^–4 N/m²
d) 30N/m²
Answer: a

Question: The temperature of the mixture of one mole of helium and one mole of hydrogen is increased from 0°C to 100°C at constant pressure. The amount of heat delivered will be
a) 600 cal
b) 1200 cal
c) 1800 cal
d) 3600 cal
Answer: b

Question: The internal energy of an ideal gas is
a) the sum of total kinetic and potential energies.
b) the total translational kinetic energy.
c) the total kinetic energy of randomly moving molecules.
d) the total kinetic energy of gas molecules.
Answer: d

Question: The correct statement of the law of equipartition of energy is
a) the total energy of a gas is equally divided among all the molecules.
b) The gas possess equal energies in all the three directions x,y and z-axis.
c) the total energy of a gas is equally divided between kinetic and potential energies.
d) the total kinetic energy of a gas molecules is equally divided among translational and rotational kinetic energies.
Answer: b

Question: The relation between the gas pressure P and average kinetic energy per unit volume E is
a) P = 1/2E
b) P = E
c) P = 3/2E
d) P = 2/3E
Answer: d

Question: 1 mole of H2 gas is contained in a box of volume V = 1.00 m³ at T =300 K. The gas is heated to a temperature of T = 3000 K 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
Answer: d

Question: The r.m.s. velocity of oxygen molecule at 16ºC is 474 m/sec. The r.m.s. velocity in m/s of hydrogen molecule at 127ºC is
a) 1603
b) 1896
c) 2230.59
d) 2730
Answer: c

Question: At constant pressure, the ratio of increase in volume of an ideal gas per degree rise in kelvin temperature to its original volume is (T = absolute temperature of the gas) is
a) T²
b) T
c) 1/T
d) 1/T²
Answer: c

Question: For hydrogen gas C_p – C_v = a and for oxygen gas C_p – C_v = b. So, the relation between a and b is given by
a) a = 16 b
b) 16 a = b
c) a = 4 b
d) a = b
Answer: d

Question: Maxwell’s laws of distribution of velocities shows that
a) the number of molecules with most probable velocity is very large
b) the number of molecules with most probable velocity is very small
c) the number of molecules with most probable velocity is zero
d) the number of molecules with most probable velocity is exactly equal to 1
Answer: a

Question: A cubic vessel (with face horizontal + vertical) contains an ideal gas at NTP. The vessel is being carried by a rocket which is moving at a speed of 500 m 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 500 ms–1 is very much smaller than vrms 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 ) / v²rms where vrms was the original mean square velocity of the gas
d) will be different on the top wall and bottom wall of the vessel
Answer: b

Question: The gases are at absolute temperature 300ºK and 350ºK respectively. The ratio of average kinetic energy of their molecules is
a) 7 : 6
b) 6 : 7
c) 36 : 49
d) 49 : 36
Answer: b

Question: If the critical temperature of a gas is 100ºC, its Boyle temperature will be approximately
a) 337.5ºC
b) 500ºC
c) 33.3ºC
d) 1000ºC
Answer: a

Question: The velocity of the molecules of a gas at temperature 120 K is v. At what temperature will the velocity be 2 v?
a) 120 K
b) 240 K
c) 480 K
d) 1120 K
Answer: c

Question: The root mean square speed of the molecules of a diatomic gas is v. When the temperature is doubled, the molecules dissociate into two atoms. The new root mean square speed of the atom is
a) √2v
b) v
c) 2v
d) 4v
Answer: c

Question: 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 the molecules.
(iv) The mean translational kinetic energy of a gas is proportional to its kelvin temperature.
a) (ii) and (iii) only
b) (i),(ii)and (iv) only
c) (i) and (iii) only
d) (iii) and (iv) only
Answer: d