## ΔS for Irreversible Expansion

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

Ariel Fern 2B
Posts: 105
Joined: Fri Aug 30, 2019 12:17 am

### ΔS for Irreversible Expansion

What equation do you use to calculate ΔS for an irreversible expansion? I know that pressure is constant and that work = -PΔV for irreversible expansion, so how does that translate into calculating ΔS? Thanks so much!

Maggie Eberhardt - 2H
Posts: 97
Joined: Sat Jul 20, 2019 12:16 am

### Re: ΔS for Irreversible Expansion

my TA mentioned that you use the same equation, only a derived version that involves heat capacity. I know that's not very descriptive sorry I don't have my notes on me right now :/

SnehinRajkumar1L
Posts: 101
Joined: Thu Jul 11, 2019 12:15 am

### Re: ΔS for Irreversible Expansion

For irreversible expansion, the only thing that changes is the values of Stotal and Ssurr. In irreversible expansion, the change in entropy of the system is the same as Stotal. Calculate S using the equations for changes in volume, but Stotal = Ssystem because Ssurr is 0.

Charisse Vu 1H
Posts: 101
Joined: Thu Jul 25, 2019 12:17 am

### Re: ΔS for Irreversible Expansion

In the book, example 4I.3 explains this concept very well! I would go through that example and read some of the information in that section, as I believe the book explains delta S in more depth than what we covered in class.