## entropy of irreversible and reversible reactions.

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

Ekayana Sethi 2K
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### entropy of irreversible and reversible reactions.

Are the entropies of irreversible and reversible reactions the same? how are they related?

Remi Lathrop 1G
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### Re: entropy of irreversible and reversible reactions.

For a reversible reaction, the key is that the ∆S(total) is equal to 0. Because ∆S + ∆S (surroundings) = ∆S (total), when ∆S (total) is 0, this means that ∆S and ∆S (surroundings) have opposite signs.

For example, if ∆S = 0.15 J/K for a reversible reaction, then ∆S (surroundings) must be equal to -0.15 J/K because together they have to add to 0.

An irreversible reaction is similar, but not the same. The ∆S will be the same in both cases, but for an irreversible reaction the ∆S (surroundings) will be 0 if your system is free expansion because there will be no outside force pushing on the reaction. Therefore ∆S + 0 = ∆S (total), so ∆S and ∆S (total) will have the same sign.

Helen Shi 1J
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Joined: Sat Jul 22, 2017 3:00 am

### Re: entropy of irreversible and reversible reactions.

I don't understand why the delta S of the surroundings is zero in an irreversible process. The textbook on page 346 says that no work is done in free expansion so w=0. Can someone explain that?