Question

The ratio of average translational kinetic energy to rotational kinetic energy of a diatomic molecule at temperature $T$ is:

• A. 3
• B. 7/5
• C. 5/3
• D. 3/2

Answer 1

Answer: (D)

3/2

For a diatomic molecule, the three translation direction contribute $1/2$ $kT$ per molecule, and for each molecule there are also two axes of rotation, contributing rotational kinetic energy in the amount of $1/2$ $kT$ each.

So total translational kinetic energy $=\left(3/2\right)kT$ & total rotational kinetic energy $=\left(2/2\right)kT$.

So, the ratio of average translational kinetic energy to rotational kinetic energy of a diatomic molecule at temperature $T$ is $\left(3/2\right)$.

Therefore, the option is D.