Question

Helium atom is two times heavier than a hydrogen molecule $\left(H_2\right)$. At $298\text{K}$, the average kinetic energy of helium atom is

• A. Two times that of a hydrogen molecule
• B. Half that of a hydrogen molecule
• C. Four times that of a hydrogen molecule
• D. Same as that of a hydrogen molecule

Answer 1

The correct option is D Same as that of a hydrogen molecule

Average kinetic energy for a helium atom is $\frac{3RT}{2N_A}$
It is independent of molar mass.
Hence $(\overline{KE}{)}_{H_2}=(\overline{KE}{)}_{He}$