Question

Helium is two times heavier than hydrogen. The average kinetic energy of the helium molecule at 300 $K$ is:

• A. 1/2 of $H_2$ molecules
• B. Two times of $H_2$ molecules
• C. Four times of $H_2$ molecules
• D. Same as that of $H_2$ molecule

Answer 1

Answer: (D)

Same as that of $H_2$ molecule

$KE=\frac{3}{2}nRT$ is the kinetic energy of gases

Kinetic energy depends on the number of moles, not on masses.

$He,H$ both are having the same number of molecules. So, they are having the same kinetic energy.

Hence option D is correct.