Kinetic Theory Of Gases Important Questions for NEET Physics - 2026

1. Multiple choice questions.

1. Which of the following is an assumption of the kinetic theory of gases?

• (a) Gaseous molecules have attraction between them
• (b) Molecular collisions are perfectly elastic
• (c) Volume of molecules is not negligible
• (d) Gases cannot be compressed

Answer: (b) Molecular collisions are perfectly elastic

2. For a gas, if the root mean square (rms) speed of molecules is $v_{rms}$, what will be the temperature if rms speed becomes double?

• (a) Doubled
• (b) Four times
• (c) Halved
• (d) Remains same

Answer: (b) Four times

3. The degree of freedom for a diatomic gas is:

• (a) 2
• (b) 3
• (c) 5
• (d) 6

Answer: (c) 5

4. The unit of mean free path is:

• (a) kg
• (b) metre
• (c) second
• (d) kelvin

Answer: (b) metre

2. Very Short Answer (VSA).

1. Define Avogadro's number.

Answer: Avogadro's number is the number of atoms or molecules present in one mole of a substance, and its value is $6.022 \times 10^{23}$.

2. What is RMS speed of gas molecules?

Answer: RMS speed of gas molecules is the square root of the average of the squares of the speeds of all molecules in a gas sample.

3. State the equation of state for a perfect gas.

Answer: The equation of state for a perfect gas is $PV = nRT$, where $P$ is pressure, $V$ is volume, $n$ is moles, $R$ is gas constant, and $T$ is temperature.

4. What is meant by mean free path?

Answer: Mean free path is the average distance a gas molecule travels between two successive collisions with other molecules.

3. Short Answer Questions.

1. Explain the kinetic interpretation of temperature in gases.

Answer: The kinetic interpretation states that temperature of a gas is a measure of the average kinetic energy of its molecules. Mathematically, average kinetic energy per molecule is $\frac{3}{2}kT$, where $k$ is Boltzmann constant and $T$ is temperature in kelvin.

2. Derive the expression for work done when a perfect gas is compressed isothermally from volume $V_1$ to $V_2$.

Answer:

1. For isothermal process, $PV = nRT$ remains constant.
2. Work done, $W = \int_{V_1}^{V_2} PdV$
3. $P = \frac{nRT}{V}$, thus $W = nRT\int_{V_1}^{V_2} \frac{dV}{V}$
4. $W = nRT \ln\left(\frac{V_2}{V_1}\right)$

3. What is the law of equipartition of energy? State its significance in specific heat of gases.

Answer: The law of equipartition of energy states that, at thermal equilibrium, each degree of freedom contributes $\frac{1}{2}kT$ energy to a molecule. For gases, this helps predict specific heat values based on available degrees of freedom.

4. True or False Questions.

1. The pressure exerted by an ideal gas is due to elastic collisions of molecules with the container walls.

Answer: True

2. According to kinetic theory, the size of a gas molecule is comparable to the volume of the container.

Answer: False

3. For a monoatomic gas, the degrees of freedom is 3.

Answer: True

3. Fill in the Blanks Questions.

1. The value of universal gas constant $R$ is _______ J mol$^{-1}$ K$^{-1}$.

Answer: 8.314

2. Mean free path depends on temperature and is _______ proportional to pressure.

Answer: inversely

3. According to kinetic theory, pressure is produced by _______ of gas molecules on the walls.

Answer: collisions

How Kinetic Theory of Gases Helps NEET Physics Aspirants

Learning Kinetic Theory of Gases helps students link molecular motion to everyday gas laws. This boosts understanding of core NEET Physics problems and equips students to solve practical questions involving gas behavior and concepts like pressure and temperature.

Key formulas, such as $PV = nRT$ and the RMS speed equation, appear regularly in NEET. By practicing these, students gain confidence in solving numerical and conceptual questions related to the Kinetic Theory of Gases.

Understanding topics like Avogadro’s number, law of equipartition of energy, and mean free path gives a solid base. Vedantu supports NEET aspirants with chapter-wise focus, tips, and exam-aligned learning for improved results.