A quantity of ideal gas (0.800mole) at a pressure of 10.0atm and 200K is allowed to
expand isothermally until it reaches a pressure of 1.00atm. Calculate the work done
if this expansion is carried out a) against a vacuum, b) against a constant external
pressure of 1.0atm and c) reversibly.
I'm not even sure where to start here. I've only calculated work done using dW = ∫ PdV. However, I'm not given an initial or final volume here, so I'm not sure how to proceed. Any hints?