Page 1 of 1

Midterm Q4A

Posted: Sun Feb 25, 2018 9:56 pm
by 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?

Re: Midterm Q4A

Posted: Sun Feb 25, 2018 10:16 pm
by 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 = -PexdeltaV

Hope this helps!

Re: Midterm Q4A

Posted: Sat Mar 10, 2018 10:16 pm
by 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.

Re: Midterm Q4A

Posted: Sun Mar 11, 2018 11:07 pm
by Mishta Stanislaus 1H
Because the external pressure was constant the process was irreversible, and that equation is for reversible processes.