Difference between deltaS(tot), deltaS and deltaS(surr)

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

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Jessica Lutz 2E
Posts: 56
Joined: Fri Sep 29, 2017 7:04 am

Difference between deltaS(tot), deltaS and deltaS(surr)

Some questions in the book (such as #47) ask you to find each of these values individually. What is the conceptual difference between each of these terms? and how what is different about how you calculate them?

vicenteruelos3
Posts: 42
Joined: Fri Sep 29, 2017 7:07 am

Re: Difference between deltaS(tot), deltaS and deltaS(surr)

one relation is that delta s of the system plus delta s of the surroundings is equal to delta s total

Lourick Bustamante 1B
Posts: 50
Joined: Wed Nov 16, 2016 3:02 am

Re: Difference between deltaS(tot), deltaS and deltaS(surr)

Yes, I agree with what is said above! DeltaS of the system added to the DeltaS of the surroundings are equal to the DeltaS total/universe. Some other points to remember are that if the calculated DeltaS total value is greater than 0, then the reaction being observed is spontaneous, and oppositely, if the DeltaS total value is less than 0, then the reaction being observed is not spontaneous. Lastly, when DeltaS = 0, then the system is at equilibrium.

Britney Alvey 1B
Posts: 31
Joined: Fri Jun 23, 2017 11:39 am

Re: Difference between deltaS(tot), deltaS and deltaS(surr)

I agree with the comments above. It is also worth noting that conceptually, deltaS(tot) is the change in entropy of the universe, the combination of deltaS and deltaS of the surroundings. DeltaS is the change in entropy of the system and deltaS(surr) is the change in entropy of the surroundings, meaning everything else besides the system.

Jessica Lutz 2E
Posts: 56
Joined: Fri Sep 29, 2017 7:04 am

Re: Difference between deltaS(tot), deltaS and deltaS(surr)

Britney Alvey 1B wrote:I agree with the comments above. It is also worth noting that conceptually, deltaS(tot) is the change in entropy of the universe, the combination of deltaS and deltaS of the surroundings. DeltaS is the change in entropy of the system and deltaS(surr) is the change in entropy of the surroundings, meaning everything else besides the system.

So when the question only asks for deltaS, do we assume they are asking for the change in entropy of the system? and if they want to know the change in entropy of the surroundings they will always specify deltaS(surr)?

Justin Chu 1G
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Re: Difference between deltaS(tot), deltaS and deltaS(surr)

Yes, when only deltaS is asked, it should be assumed to be the entropy change for the system only. Anything else would have to be specified.

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