Question

Helium atom is two times heavier than a hydrogen molecule. At $298\, K$ the average kinetic energy of a helium atom is

• A. two times that of a hydrogen molecule
• B. same as that of a hydrogen molecule
• C. four times that of hydrogen molecule
• D. half that of a hydrogen molecule

Answer 1

Answer: (B)

same as that of a hydrogen molecule

Answer 2

According to kinetic theory, average kinetic energy $(\in)=\frac{3}{2}k_B T$
where, $k_B$ is Boltzmann- constant. Since, it is independent of molar mass, it will be same for He and $H_2$ at a given temperature.