# Homework Help: Entropy and Adiabatic Expansion

1. Feb 28, 2012

### Rapier

1. The problem statement, all variables and given/known data
Argon gas, initially at pressure 100 kPa and temperature 300 K, is allowed to expand adiabatically from 0.01 m3 to 0.029 m3 while doing work on a piston.

In this problem you will calculate the contributions to the entropy change, as discussed in Moore, T7.4.

a) What is the change in entropy due to the volume change alone, ignoring any effects of changing internal energy?
DS = 3.549 J/K *
OK

b) If the expansion is adiabatic, what is the final temperature?

Tf = K

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Part A was fairly easy. We're doing homework in arears. We are already on to special relativity so I'm trying to remember entropy (and a lot of this seems to be going back even further to PV diagrams which was 2 units ago). I'm struggling to remember how to do this. There are more questions to this problem, but they all stem around part B.

2. Relevant equations
PV = nRT -> I calculated that there are .4009 moles.
From my number of moles and the molar mass of argon I know that my sample weighs 16.02 g.

3. The attempt at a solution

I had a couple of equations but I keep needing P1 AND T1. I need another equation. Can someone please provide some guidance?