`C_(v)` values of He is always `(3R)/(2)` but `C_(v)` values of `H_(2)` is `(3R)/(2)`
at low temperature and `(5R)/(2)` at higher temperature explain .

Explanation

Helium is a monatomic gas and it possesess only three degrees of freedom corresponding to translational motion.
`C_(V) = (3)/(2)R`
Hydrogen is a diatomic molecule, but at lower temperature, contributions of rotational and vibrational motion are neglected. Therefore, there are three degrees of freedom.
`C_(V) = (3)/(2)R`
At higher temperatures, rotational motion also contributes, so degrees of freedom become `5` in total.
`C_(V) = (5)/(2)R`