Q 11-12-038JEE MainJEE Main 2025 (28 Jan, Shift 2)Easy
The ratio of vapour densities of two gases at the same temperature is $\dfrac{4}{25}$, then the ratio of r.m.s. velocities will be
Answer: (C) $\dfrac{5}{2}$
Vapour density is proportional to molar mass, and $v_{rms} = \sqrt{\dfrac{3RT}{M}}$, so at the same temperature
$$\frac{v_1}{v_2} = \sqrt{\frac{M_2}{M_1}} = \sqrt{\frac{25}{4}} = \frac{5}{2}$$
Solution by Sreeraj P, M.Sc Physics