Question

Assertion :The average translational kinetic energy per molecule of the gas per degree of freedom is $\frac{1}{2}KT$. Reason: For every molecule there are three rotational degree of freedom.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is C Assertion is correct but Reason is incorrect

Average translational energy for one molecule of gas is $\frac{1}{2}{k}_{B}T$ for each co-ordinate axis i.e. x, y and z. Since the molecule can move in the three-dimensional space.

whereas the rotational degree of freedom is 0 for monoatomic gases, 2 for diatomic and 3 for the non-linear molecule. The two are not related.

Thus, Assertion is correct but Reason is incorrect

Hence, the correct option is $\text{C}$