The molar heat capacity of oxygen gas at `STP` is nearly `2.5 R`. As the temperature is increased, it gradually increase and approaches `3.5 R`. The most appropriate reason for this behaviour is that at high temperatures

Options

A. oxygen does not behave as an ideal gas
B. oxygen molecules dissociate in atoms
C. the molecules collides more frequently
D. molecular vibration gradually becomes effective

Answer

D

Explanation

`C_(v)=2.5 R`
As temperature increases, vibrational degree of freedom becomes 2 at high temperature
`C_(v)=7/2 R =3.5R`