Given below are two statements: one is labelled as Assertion (A)...

The mean free path of gas molecules is given by $\lambda = \dfrac{1}{\sqrt{2}\pi d^2 n}$, where $n$ is the number density ($n = \dfrac{N}{V}$).

In a closed rigid vessel, both the total number of molecules ($N$) and the volume ($V$) remain constant. Therefore, the number density ($n$) is constant.

Since $\lambda$ depends only on the molecular diameter and number density, it remains constant even if the temperature is increased. Thus, Assertion (A) is correct.

Reason (R) is incorrect because the mean free path is independent of temperature as long as the volume (and thus number density) is constant.

Answer: (A) is correct but (R) is not correct