Midterm Q4A

[Yea Eun Lee 1H]

A piston containing 0.10 mol of nitrogen gas at 298 K has an initial volume of 2.24 L and
undergoes an expansion against 0.5 atm external pressure until its volume doubles.
Calculate the work involved in Joules.

How come for this problem we don't use the equation -nRT ln V2/V1?

[Kyle Sheu 1C]

That would be because the -nRTlnV2/V1 equation is used for reversible, isothermal expansion; because the problem describes expansion against a constant, external pressure of 0.5 atm, we'd use w = -P_exdeltaV

Hope this helps!

[lizzygaines1D]

yeah just to add on and clarify because this problem was tricky and there was info given that you didn't need. the external pressure never changed throughout the reaction.

[Mishta Stanislaus 1H]

Because the external pressure was constant the process was irreversible, and that equation is for reversible processes.