Free Expansion


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Emily Glaser 1F
Posts: 156
Joined: Thu Jul 27, 2017 3:01 am

Free Expansion

Postby Emily Glaser 1F » Mon Feb 12, 2018 3:00 pm


delta U=0
delta H=0

in a free expansion?

Can free expansion only occur in an isolated system? Are they synonymous?

K Stefanescu 2I
Posts: 68
Joined: Fri Sep 29, 2017 7:04 am

Re: Free Expansion

Postby K Stefanescu 2I » Mon Feb 12, 2018 4:53 pm

The condition of free expansion only tells us that w=0. q and U are not necessarily also zero in all cases of free expansion.

Aya Shokair- Dis 2H
Posts: 58
Joined: Fri Sep 29, 2017 7:07 am

Re: Free Expansion

Postby Aya Shokair- Dis 2H » Mon Feb 12, 2018 5:54 pm

No work is done in a free expansion, thus w=0.
If it was a isothermal free expansion, you can go on to say delta U= 0.
So that w=-q. since w=0, q=0.

You can go on even further to say whether its a irreversible or reversible process.
If it is a reversible process, then the process is at equilibrium, so delta S tot= 0.
So, delta S sys= - delta S surr

IF the process is irreversible, the you can say since there is no heat or work being released or done on the surroundings, delta S surr=0, thus delta S sys= delta S tot.

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