Entropy in reversible and irreversible

[Diana_Diep2I]

What is the difference in entropy when it comes to a reversible reaction? Irreversible? Do we calculate it the same way using the deltaS=nRln(V2/V1)?

[nehashetty_2G]

I don't think it matters for entropy. I believe we always use the RTln(V2/V1).

[Samuel G Rivera - Discussion 4I]

For reversible you would use delta S = nRln(V2/V1). For isothermal irreversible free expansion you would use the same equation. The difference is that the change in entropy of the surroundings is - delta S for reversible and 0 for irreversible.

[Abhi Vempati 2H]

Since entropy is a state function and the path between initial and final states doesn't matter, the entropy of the system is nRln() for both reversible and irreversible expansion.

However, as @Samuel G Rivera - Discussion 4I mentioned, the main difference is what happens to the entropy of the surroundings. For reversible expansion (which is typically isothermal), , so . However, for irreversible expansion, the surroundings don't have time to react to the expansion of the system, so . This means that .

*Note that refers to the change in entropy of the system.

Hope this helps!