Question

The mean rotational kinetic energy of diatomic molecule at temperature t is

Answer 1

According to law of equipartition of energy, a molecule can have 1/2 KT energy per degree of freedom.

A diatomic molecule has two rotational degrees of freedom. Hence the total rotational kinetic energy is KT

Answer 2

•The mean rotational kinetic energy is given by the Principle of equipartition of energy which states that "The mean(average) kinetic energy of every degree of freedom of a molecule is kT/2".

•Mean(average) kinetic energy per molecule <K> = fkT/2 = fRT/2

Where, f is degree of freedom, and

T is absolute temperature.

•For a diatomic molecule, degree of freedom = 2.

•Hence, the mean rotational kinetic energy = 2kT/2 = kT.