The specific heats, `C_(P)` and `C_(V)` of a gas of diatomic molecules, A are given (in units of `Jmol^(-1) K^(-1)`) by 29 and 22 , respectively. Another gas of diatomic molecules , B has the corresponding values 30 and 21. if they are treated as ideal gases, then :

Options

A. A is rigid but B has a vibrational mode
B. Both A and B have a vibrational mode each
C. A has on vibrational mode and B has two
D. A has a vibrational mode but B has none

Answer

D

Explanation

For A `R=C_p-C_v=7`
`C_v= (fR)/(2)=22 implies f=(44)/(7)=6.3`

For B `R=C_p-C_v=9`
`C_v=(fR)/(2)=21 implies f= (42)/(9)`