# Thermodynamics: finding work done

## Homework Statement

In a closed system 0.4kg of gas at 374K is expanded isothermally and reversibly from 1MPa pressure to 300kPa. Given that Cv = 718j/kg and R = 287j/kg, determine the work done.[/B]

## Homework Equations

Not sure? I guess W = p*V?

## The Attempt at a Solution

I honestly don't know how to solve this one.

NB: I don't want anyone to do this for me, in case anyone thinks I'm trying to cheat. I just want someone to point me in the right direction because I honestly don't know where to begin figuring this out.

Chestermiller
Mentor
What is the equation for the differential work dW done by a gas on its surroundings in terms of the external force per unit area Pext and the differential change in volume dV? For a reversible process, how is the external force per unit area Pext related to the gas pressure?

Chet

What is the equation for the differential work dW done by a gas on its surroundings in terms of the external force per unit area Pext and the differential change in volume dV? For a reversible process, how is the external force per unit area Pext related to the gas pressure?

Chet
Chet, I'm sure this is an algebra based physics question, not calculus.

Chestermiller
Mentor
Chet, I'm sure this is an algebra based physics question, not calculus.
Really. What makes you think so? This problem can not be solved correctly unless PdV is integrated, or the person has a formula for the result of the PdV integration.

Chet