[ahhppull]

1 mole of an ideal monatomic gas undergoes reversible adiabatic expansion from 24.8 liter at 298 K to 49.6 liter. How much work is done by the system?

I'm not quite sure what equation to use.  The way I just did it was Tf = Ti(Vi/Vf)^1/c, solving for Tf.  Then, I used W = CvΔT where Cv = 3/2nR. I got -1375 J.

[ahhppull]

I'm sorry.  I just realized that since the volume is changing, I would not be able to use Cv.