[eagerinsight]

If I have a sample consisting of 1.00 mol of an ideal gas and it is expanded isothermally at 0°C from .0224 m3 to .0448 m3.

I have to calculate q and w for the following
(a) reversibe expansion
(b) against a constant external pressure equal to the final pressure of the gas
(c) against zero external pressure

I calculated w
(a) using w=-nRT ln(Vf/Vi)
(b) using w=-Pfinal(Vf-Vi) where Pfinal=nRT/Vf
(c) With no external pressure is w=0 ???

As for heat transfer q, I have no idea where to start, I can't use q=CdeltaT because deltaT=0 because it is isothermic, does this mean q=w? Any pointers where to start? Is case (c) and adiabatic system?

[Yggdrasil]

You have the correct equations for calculating work in all three cases.  You are also correct that for an isothermal process, the internal energy does not change and the amount of work done by the system equals the amount of heat transferred to the system.