# Isothermally Expanding Question

1. Oct 8, 2013

### PsychonautQQ

1. The problem statement, all variables and given/known data
Two moles of an ideal gas are compressed in a cylinder at a constant temperature at 338K until the original pressure is tripled. Calculate the amount of work done.

2. Relevant equations
PV=nRT
PV/T = c

3. The attempt at a solution
I don't know how to incorporate the cylinder information into this problem.. or get anywhere at all really.
3Pi = Pf
does this lead to Vi = 3Vf? since PV/T = c and T doesn't change?

W = PdV = nRdT..?
..halppp;-(

2. Oct 8, 2013

### Staff: Mentor

Yes.

No, that doesn't make sense since P is not constant and T is.

You need the formula for work as an integral over dV and use the ideal gas law to substitute for T which is constant.

3. Oct 8, 2013

### Staff: Mentor

If the temperature is constant, what is the ratio of the initial volume to the final volume? Your equation for the work is correct (if you use the convention that dW is the work done on the surroundings by the system). Just substitute nRT/V for P and integrate.

Chet