Degrees of Freedom and Molar Specific Heats

[mit_hacker]

Homework Statement

We give 70J as heat to a diatomic gas, which then expands at constant pressure. The gas molecules rotate but do not oscillate. By how much does the internal energy of the gas increase.

Homework Equations

The Attempt at a Solution

I did it this way:
Heat added = nCp dT = 70J.
Let Internal energy = nCv dT = x (say).
Dividing both equations, we obtain:
Cp/Cv = 70/x.
But, Cp/Cv is nothing but the ration of speicifc heat which for a diatomic gas is known to be 7/5. So, x = 50J.

Am I correct? the solution is not given in the book!

Thanks a ton in advance!

 

[FedEx]

It is an isobaric process.

Your answer is 100% correct.

 

[mit_hacker]

Thanks a ton!

Thank-you so very much. I really appreciate it.