# Irreversible Adiabatic Expansion (Physical Chemistry)

1. Apr 13, 2013

### djh101

1. The problem statement, all variables and given/known data
Consider the adiabatic expansion of .553mol of an ideal monatomic gas with CV,m = 3R/2. The initial state is described by P = 6.25bar and T = 306K. Calculate the final temperature if the same gas undergoes an adiabatic expansion against an external pressure of P = 1.25bar to a final pressure P = 1.25bar.

2. Relevant equations
CVΔT = -PextΔV

3. The attempt at a solution
I need to find ΔT. P, V, and T are all variables, though, so I can't find ΔT because I don't know ΔV. What do I do?

2. Apr 13, 2013

### Staff: Mentor

Use the ideal gas law to express the final volume algebraically in terms of the final temperature. Substitute this into your equation. The final temperature will be on both sides of the resulting equation. Collect terms involving the final temperature, and solve for it.

3. Apr 13, 2013

### djh101

A little bit of annoying algebra, but I got it. Thank you very much.