What Type of Gas Can Be Used for Isothermal and Adiabatic Energy Storage?

[Claire84]

We've been set the question of- In an isothermal expansion, and ideal gas at initial pressure Po expands until its volume is twice its initial volume. When the gas is compressed adibatically and quasi-statically ack to its original volume, its pressure is 1.32Po. Is the gas monatomic, diatomic or polyatomic? How does the translational kinetic energy of the gas change in these processes? We can assume throughout that the gas is in the regime where rotational motion takes plae, but vibraional motion is frozen out.

I wouldnhave said that the translational minietic energy increased throughout, but how specific would I need to be really? Also, I have no idea about what type of gas it is. Any help would be much appreciated. Thanks!

 

[Claire84]

For a monatomic gas I know that the change in internal energy is equal to 3/2nRchange in temp and for diatomic it's 5/2nRchange in T (I think), so do I need to look at the various internal energies to decide what type of gas it is or is there a much simpler solution? I've been looking at loads of textbooks but to no avail and my brain is completely fried because it's obviously not a hard question.

 

[Claire84]

Is it a diatomic gas because when you work out gamma for the adiabatic process you get 1.4? I just checked this at a website and stuff, but I never knew that gamma would equal this for a diatomic gas. Is this something you should know or is there some way of deriving it?