# Work of isothermal compression at constant pressure

1. Sep 26, 2015

### ColtonCM

The Problem:

A 1.80 mol sample of an ideal gas is compressed isothermally from 58.1 L to 15.6 L using a constant external pressure of 2.72 atm .

Calculate W:

Calculate Q:

Calculate ΔU:

Attempt at solution:

I tried W = P(ΔV) to no effect, W = nRTln[Vf/Vi] to no effect. The online submission form tells me if the sign is wrong so I know that the numbers I got from these two equations are not correct as if they were and the sign was wrong it would have told me. I used 273K as T since T is not given.

Any help would be appreciated. Due at midnight and friends have all remained oddly out of contact.

I can't go for Q and U until I figure out the first part.

Thanks,

Colton

2. Sep 26, 2015

### Staff: Mentor

Well, if the external force per unit area is held constant at 2.72 atm, the work should be PΔV = -115.6 liter-atm. What units do they want the answer in?

If the initial and final temperatures of an ideal gas are the same (isothermal), what is ΔU?

Chet