The molar heat capacity, `C_(v)` of helium gas is `3//2` R and is independent of temperature. For hydrogen gas, `C_(v)` approaches `3//2` R at a very low temperature, equals `5//2` R at moderate temperature and is higher than `5//2` R at high temperature. Choose the correct reason for the temperature dependence of `C_(v)` in case of hydrogen :

Options

A. Hydrogen is diatomic so at high temperature rotational and vibrational motion also counts
B. Hydrogen is monoatomic so at high temperature rotational and vibrational motion also counts
C. Hydrogen is diatomic so at high temperature rotational and vibrational motion are not counted
D. can’t be defined

Answer

A