Q 11-12-144JEE MainJEE Main 2019 (9 Apr, Shift 1)Easy
An HCl molecule has rotational, translational and vibrational motions. If the rms velocity of HCl molecules in its gaseous phase is $\bar v$, $m$ is its mass and $k_B$ is Boltzmann's constant, then its temperature will be
Answer: (C) $\dfrac{m\bar v^2}{3k_B}$
The rms velocity is set only by the translational kinetic energy, which is $\frac32k_BT$ per molecule whatever the other modes:
$$\frac12m\bar v^2 = \frac32k_BT \Rightarrow T = \frac{m\bar v^2}{3k_B}$$
Solution by Sreeraj P, M.Sc Physics