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### ΔS for Irreversible Expansion

Posted: **Sun Feb 16, 2020 11:07 pm**

by **Ariel Fern 2B**

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!

### Re: ΔS for Irreversible Expansion

Posted: **Sun Feb 16, 2020 11:25 pm**

by **Maggie Eberhardt - 2H**

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 :/

### Re: ΔS for Irreversible Expansion

Posted: **Sun Feb 16, 2020 11:26 pm**

by **SnehinRajkumar1L**

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.

### Re: ΔS for Irreversible Expansion

Posted: **Sun Feb 16, 2020 11:31 pm**

by **Charisse Vu 1H**

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.