Kinetic Theory NEET Questions with Solutions

Q: How many questions come from Kinetic Theory in NEET 2027?

You can expect 1 to 2 questions from Kinetic Theory in NEET 2027. The chapter has medium PYQ frequency. RMS speed, kinetic temperature, equipartition of energy and specific heats from degrees of freedom are the most repeated topics.

Q: What is the formula for the pressure of an ideal gas in kinetic theory?

P equals one third of rho times v_rms squared, where rho is the mass density of the gas and v_rms is the root mean square speed. Equivalently, P V equals one third of N m v_rms squared, with N the number of molecules and m the mass of each molecule. This derivation assumes elastic collisions with the container walls and isotropic molecular motion.

Q: What is the kinetic interpretation of temperature?

Temperature is a direct measure of the average translational kinetic energy of the molecules. Specifically, the average translational KE per molecule equals three halves k_B T, where k_B is the Boltzmann constant 1.38 times 10 to the minus 23 J per K. So at a higher temperature, the molecules move faster on average.

Q: How do RMS speed, average speed and most probable speed compare?

For a Maxwell-Boltzmann distribution, v_p (most probable) is the smallest, then v_avg, then v_rms is the largest. The ratios are v_p : v_avg : v_rms equals approximately 1 : 1.128 : 1.224. v_rms equals the square root of (3 R T over M), v_avg equals the square root of (8 R T over pi M), v_p equals the square root of (2 R T over M).

Q: What is the equipartition theorem?

Each quadratic degree of freedom of a molecule carries an average energy of half k_B T. So a monoatomic gas (3 translational degrees) has three halves k_B T per molecule. A diatomic gas at room temperature (3 translational plus 2 rotational) has five halves k_B T per molecule. This is why Cv equals (f over 2) R per mole.

Q: What is the mean free path of a gas molecule?

The mean free path lambda is the average distance a molecule travels between successive collisions. lambda equals 1 over (square root of 2 times pi d squared n), where d is the molecular diameter and n is the number density. At standard conditions for air, lambda is about 70 nanometres, far larger than the molecular size.

Q: When does an ideal gas law fail?

The ideal gas law P V equals n R T fails at high pressures (where molecular volumes matter) and at low temperatures (where intermolecular forces matter). Real gases are described by the van der Waals equation. For NEET problems, you can almost always treat the gas as ideal unless the question explicitly says otherwise.

Question 1

The mean free path of molecules of a gas, (radius ‘r’) is inversely proportional to -

Accepted Answer

r 2

Question 2

Two vessels separately contain two ideal gases A and B at the same temperature, the pressure of a being twice that of B. Under such conditions, the density of A is found to be 1.5 times the density if

Accepted Answer

3 4

Question 3

The molecules of a given mass of a gas have r.m.s velocity of 200 ms−1 at 27oC and 1.0 ×105 Nm−2 pressure. When the temperature and pressure of the gas are respectively, 127oC and 0.05× 105 Nm−2, the

Accepted Answer

400 √3

Question 4

A gas mixture consists of 2 moles of O 2 and 4 moles of Ar at temperature T. Neglecting all vibrational modes, the total internal energy of the system is

Accepted Answer

11 RT

Question 5

At what temperature will the rms speed of oxygen molecules become just sufficient for escaping from th e Earth’s atmosphere ? (Given : Mass of oxygen molecule (m) = 2·76 × 10 – 26 kg Boltzmann’s const

Accepted Answer

8·360 × 10 4 K

Question 6

The mean free path for a gas, with molecular diameter d and number density n can be expressed as :

Accepted Answer

1 2 n d π

Question 7

Match Column - I and Column - II and choose the correct match from the given choices. Column - I Column - II (A) Root mean square (P) 2 1 nm 3 v speed of gas molecules (B) Pressure exerted (Q) 3 RT M

Accepted Answer

- (R),

Question 8

The temperature of a gas is –50° C. To what temperature the gas should be heated so that the rms speed is increased by 3 times?

Accepted Answer

3295° C

Kinetic TheoryNEET Physics · Class 11 · NCERT Chapter 12

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Kinetic TheoryNEET Physics · Class 11 · NCERT Chapter 12

1NEET 2014Medium4 bookletsThe mean free path of molecules of a gas, (radius ‘r’) is inversely proportional to -

2NEET 2015Medium4 bookletsTwo vessels separately contain two ideal gases A and B at the same temperature, the pressure of a being twice that of B. Under such conditions, the density of A is found to be 1.5 times the density if B. The ratio of molecular weight of A and B is:

3NEET 2016Medium4 bookletsThe molecules of a given mass of a gas have r.m.s velocity of 200 ms−1 at 27oC and 1.0 ×105 Nm−2 pressure. When the temperature and pressure of the gas are respectively, 127oC and 0.05× 105 Nm−2, the r.m.s. velocity of its molecules in ms−1 is: www.vedantu.com 17

4NEET 2017Medium5 bookletsA gas mixture consists of 2 moles of O 2 and 4 moles of Ar at temperature T. Neglecting all vibrational modes, the total internal energy of the system is

5NEET 2018Hard20 bookletsAt what temperature will the rms speed of oxygen molecules become just sufficient for escaping from th e Earth’s atmosphere ? (Given : Mass of oxygen molecule (m) = 2·76 × 10 – 26 kg Boltzmann’s constant k B = 1·38 × 10 – 23 J K – 1 )

6NEET 2020Medium23 bookletsThe mean free path for a gas, with molecular diameter d and number density n can be expressed as :

8NEET 2023Medium24 bookletsThe temperature of a gas is –50° C. To what temperature the gas should be heated so that the rms speed is increased by 3 times?

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