irreversible and isothermal work

[cns]

I know work for reversible + isothermal is w=nRTln(v2/v1) but what about irrev? I see the equation W=P(delta V) used all the time. Is this the correct one to use? or is there another equn for irreversible work for a gas?

THanks

[rock.freak667]

Due to irreversibility you would get entropy generation which would take away from the useful work output. You might need to subtract the effect of the entropy generation.