## Entropy - Reversible vs Irreversible

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

Alexis Elliott 1J
Posts: 28
Joined: Wed Sep 21, 2016 2:59 pm

### Entropy - Reversible vs Irreversible

During lecture I understood that if we want to calculate the enthalpy and the change is irreversible we use w=-P(V2-V1), and if it is irreversible we use w=-nRTln(V2/V1).

My question is regarding entropy. Is there a different set of equations we should use based on whether the reaction is reversible or irreversible? Or is there only this difference when it comes to enthalpy?

Tycho_Meimban_2B
Posts: 31
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Entropy - Reversible vs Irreversible

Entropy is produced in irreversible processes, and reversible processes do not produce any entropy at all.

All real process, such as mixing two gases, spontaneous combustion, and the transfer of heat, are not reversible at all, but we can find a measure of entropy for each of these processes.

Hope this helps!

Alexis Elliott 1J
Posts: 28
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Entropy - Reversible vs Irreversible

Thank you!!

The only other question I have is why isn't there an entropy change in reversible reactions?

Patrick Ricaflanca 2H
Posts: 21
Joined: Sat Jul 09, 2016 3:00 am

### Re: Entropy - Reversible vs Irreversible

I think it may have something to do with entropy being a state function. So if the reaction returns to the same state it was in before, then there was no change.