Constant Pressure and Volume


and

Moderators: Chem_Mod, Chem_Admin

Sarah Sharma 2J
Posts: 33
Joined: Fri Sep 29, 2017 7:05 am

Constant Pressure and Volume

Postby Sarah Sharma 2J » Tue Feb 13, 2018 11:24 am

When calculating for entropy, when will we know when to implement 5/3 R and 3/2 R for an expression? Are there any hints in the equation other than "at constant pressure/volume?"

Chem_Mod
Posts: 19157
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 827 times

Re: Constant Pressure and Volume

Postby Chem_Mod » Tue Feb 13, 2018 4:52 pm

Hi, Sarah,
3/2 R is a molar heat capacity at constant volume, while 5/2 R is at constant pressure. Whenever, in the question, the volume or pressure is not changing, you can use 3/2R or 5/2 for C respectively. Just check if there is any information whether the pressure is changed. If not, use 5/2R. Same for volume.


Return to “Calculating Work of Expansion”

Who is online

Users browsing this forum: No registered users and 2 guests