Q.1 According to the kinetic theory of gases, pressure of a gas arises due to:
Gravitational pull of Earth
Elastic collisions of molecules with the walls
Magnetic interactions between molecules
Electrostatic forces
Explanation - The pressure exerted by a gas is due to molecules colliding elastically with the container walls, transferring momentum.
Correct answer is: Elastic collisions of molecules with the walls
Q.2 The root mean square speed of a gas molecule is proportional to:
√T
T
1/√T
1/T
Explanation - RMS speed of molecules is given by √(3kT/m), which depends on the square root of temperature.
Correct answer is: √T
Q.3 At constant temperature, the average kinetic energy of a gas molecule depends on:
Type of gas
Temperature
Volume of container
Pressure
Explanation - The average kinetic energy is proportional only to absolute temperature and independent of the type of gas.
Correct answer is: Temperature
Q.4 Which of the following gases will have the highest RMS speed at the same temperature?
Oxygen
Nitrogen
Helium
Carbon dioxide
Explanation - At the same temperature, lighter gases have higher RMS speeds. Helium has the lowest molar mass.
Correct answer is: Helium
Q.5 The value of Boltzmann constant (k) is:
1.38 × 10^-23 J/K
8.31 J/mol-K
6.02 × 10^23 J
9.11 × 10^-31 J
Explanation - Boltzmann constant relates average kinetic energy of particles to temperature: k = R/NA.
Correct answer is: 1.38 × 10^-23 J/K
Q.6 Which law can be derived from kinetic theory assuming negligible intermolecular forces?
Boyle’s law
Charles’ law
Avogadro’s law
All of these
Explanation - The ideal gas laws (Boyle’s, Charles’, Avogadro’s) are direct consequences of kinetic theory under ideal conditions.
Correct answer is: All of these
Q.7 The mean free path of molecules is the:
Average velocity of molecules
Average distance between two collisions
Distance traveled by sound in gas
Square root of kinetic energy
Explanation - Mean free path is the average distance a molecule travels between successive collisions.
Correct answer is: Average distance between two collisions
Q.8 Equipartition theorem states that:
Energy is equally divided between all states
Each degree of freedom has average energy (1/2)kT
All molecules have same velocity
Energy distribution is independent of temperature
Explanation - According to equipartition theorem, each quadratic degree of freedom contributes (1/2)kT to energy.
Correct answer is: Each degree of freedom has average energy (1/2)kT
Q.9 If the temperature of a gas is doubled, the RMS speed of molecules becomes:
Twice
Four times
√2 times
Half
Explanation - RMS speed ∝ √T. Doubling temperature increases speed by √2.
Correct answer is: √2 times
Q.10 The pressure of an ideal gas at constant volume is directly proportional to:
1/T
√T
T
1/√T
Explanation - At constant volume, from ideal gas law, P ∝ T.
Correct answer is: T
Q.11 The internal energy of an ideal monatomic gas depends on:
Pressure only
Volume only
Temperature only
Both pressure and volume
Explanation - Internal energy of an ideal monatomic gas = (3/2)nRT, depending only on T.
Correct answer is: Temperature only
Q.12 Which of the following is NOT an assumption of kinetic theory?
Molecules are in constant random motion
Collisions are perfectly elastic
Intermolecular forces are negligible
Molecules lose energy after collisions
Explanation - Kinetic theory assumes perfectly elastic collisions where no energy is lost.
Correct answer is: Molecules lose energy after collisions
Q.13 What is the ratio of RMS speed to average speed of a gas molecule?
1
1.085
1.224
1.414
Explanation - RMS speed : Average speed ≈ 1.085 for Maxwell distribution.
Correct answer is: 1.085
Q.14 What is the ratio of most probable speed to RMS speed of a gas molecule?
1
0.816
1.224
1.414
Explanation - Most probable speed = √(2RT/M), RMS speed = √(3RT/M). Ratio = √(2/3) ≈ 0.816.
Correct answer is: 0.816
Q.15 The kinetic theory of gases explains:
Laws of reflection
Gas laws
Electromagnetic induction
Nuclear fission
Explanation - Kinetic theory provides microscopic explanation of macroscopic gas laws.
Correct answer is: Gas laws
Q.16 Degrees of freedom of a monoatomic gas molecule are:
1
2
3
6
Explanation - A monoatomic gas has 3 translational degrees of freedom.
Correct answer is: 3
Q.17 For a diatomic gas at room temperature, the molar specific heat at constant volume is approximately:
(3/2)R
(5/2)R
(7/2)R
(9/2)R
Explanation - At room temperature, a diatomic gas has 5 active degrees of freedom, hence Cv = (5/2)R.
Correct answer is: (5/2)R
Q.18 Avogadro’s number is approximately:
3.0 × 10^8
6.02 × 10^23
1.38 × 10^-23
9.11 × 10^-31
Explanation - Avogadro’s number gives the number of molecules in one mole of a substance.
Correct answer is: 6.02 × 10^23
Q.19 In kinetic theory, the distribution of molecular speeds is given by:
Newton’s law
Maxwell-Boltzmann distribution
Boyle’s law
Fourier series
Explanation - The distribution of molecular speeds in a gas is described by Maxwell-Boltzmann distribution law.
Correct answer is: Maxwell-Boltzmann distribution
Q.20 At STP, the volume occupied by one mole of an ideal gas is:
22.4 L
1 L
6.022 L
0.082 L
Explanation - At standard temperature and pressure, 1 mole of an ideal gas occupies 22.4 liters.
Correct answer is: 22.4 L
Q.21 The speed of sound in a gas depends on:
Pressure
Volume
Temperature
Type of container
Explanation - Speed of sound in a gas is proportional to √(γRT/M), thus depends on temperature and gas properties.
Correct answer is: Temperature
Q.22 If the kinetic energy of gas molecules is doubled, the temperature becomes:
Half
Twice
Four times
Unchanged
Explanation - Average kinetic energy is directly proportional to absolute temperature. Doubling KE doubles T.
Correct answer is: Twice
Q.23 The unit of gas constant R is:
J/mol-K
J/kg-K
K/mol
Pa
Explanation - Universal gas constant R has units J/mol-K.
Correct answer is: J/mol-K
Q.24 Which of the following increases with temperature for an ideal gas?
RMS speed
Molar mass
Avogadro’s number
Gas constant
Explanation - RMS speed ∝ √T, while other quantities remain constant.
Correct answer is: RMS speed
Q.25 The ratio of specific heats (Cp/Cv) for a monoatomic ideal gas is:
4/3
5/3
7/5
1
Explanation - For monatomic gases, Cv = (3/2)R, Cp = (5/2)R, so γ = Cp/Cv = 5/3.
Correct answer is: 5/3