Question

For an isothermal process, the work done by or on a system of ideal gas is equal to the change in what?

Answer 1

Isothermal process is that there is not any change in temperature during the process.

So, you can get the answer by using ideal gases law ..

Answer 2

The work done depends on two things: change in pressure and change in temperature. Since the process is isothermal (no change in temperature), the work is equal to the change in pressure.