# The specific heats, cp and cv of a gas of diatomic molecules, A, are given (in units of j mol−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: (a) A is rigid but B has a vibrational mode. (b) A has a vibrational mode but has none. (c)  Both A and B have a vibrational mode each. (d) A has a vibrational mode and B has two.

## Question ID - 51267 | SaraNextGen Top Answer The specific heats, cp and cv of a gas of diatomic molecules, A, are given (in units of j mol−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: (a) A is rigid but B has a vibrational mode. (b) A has a vibrational mode but has none. (c)  Both A and B have a vibrational mode each. (d) A has a vibrational mode and B has two.

Answer Key / Explanation : (b) -

For (A)CP=29, CV=22

For(B)CP=30 CV=22

∴     = = =1.31

When A has vibrational degree of freedom, then = =1.29.

= = =1.42

B has no vibrational degree of freedom