Q 11-12-166JEE MainJEE Main 2025 (7 Apr, Shift 2)Easy
Helium and argon are put in a flask at the same room temperature ($300\ \text{K}$). The ratio of the average kinetic energies (per molecule) of helium and argon is: (Given: molar mass of helium = $4\ \text{g/mol}$, molar mass of argon = $40\ \text{g/mol}$)
Answer: (D) $1 : 1$
Both are monoatomic, with only 3 translational degrees of freedom, so each molecule has average kinetic energy $\tfrac32k_BT$, independent of its mass. At the same temperature the ratio is $1 : 1$.
Solution by Sreeraj P, M.Sc Physics