What w equation to use


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Rachel Wang
Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

What w equation to use

Postby Rachel Wang » Fri Mar 16, 2018 6:29 pm

I'm a little confused under what conditions do we use

W = - P x ∆V
or
w = -nRT ln V2

Gwyneth Huynh 1J
Posts: 30
Joined: Fri Sep 29, 2017 7:05 am

Re: What w equation to use

Postby Gwyneth Huynh 1J » Fri Mar 16, 2018 7:01 pm

Use W = - P x ∆V for irreversible expansions (pressure is constant). On the other hand, use W = -nRT ln (V2/V1) or W = -nRT ln (P1/P2) for reversible expansions (pressure is not constant).

704887365
Posts: 49
Joined: Sat Jul 22, 2017 3:00 am

Re: What w equation to use

Postby 704887365 » Fri Mar 16, 2018 7:42 pm

Use the first equation for irreversible reactions (constant pressure) and the second for reversible reactions (dynamic pressure)

Kristin Ishaya 1A
Posts: 30
Joined: Fri Sep 29, 2017 7:04 am

Re: What w equation to use

Postby Kristin Ishaya 1A » Sat Mar 17, 2018 5:23 pm

Was question 4A from the midterm a reversible expansion problem? I didn't know which formula to use so I did it both ways.

Rachel Wang
Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

Re: What w equation to use

Postby Rachel Wang » Sat Mar 17, 2018 5:32 pm

Kristin Ishaya 1A wrote:Was question 4A from the midterm a reversible expansion problem? I didn't know which formula to use so I did it both ways.


I was confused too, actually, but because pressure was constant I think it's w=-PdeltaV

Troy Tavangar 1I
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

Re: What w equation to use

Postby Troy Tavangar 1I » Sun Mar 18, 2018 1:15 am

The first is for irreversible and the second is for reversible.


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