Question

A gas is allowed to expand at a constant pressure of 10^7 Pa, its volume increasing by 2 m^3. It is then cooled at a constant volume, and its pressure drops to 5*10^6 Pa. Finally, it is returned at constant pressure to its original volume. What is the net work done by the gas during the entire process?

Answer 1

The work done by a gas at pressure P when it expands (reversibly) by a small amount dV, is PdV.
To find the work done in a large change of volume, you should integrate PdV, but in your case the pressure remains constant so you can just use P(Vfinal-Vinitial) to find the work done by the gas.

Answer 2

You have to consider the expansion and compression stages separately, then find the net work done when you've worked out the work done in each stage.