## Comparing 9.1 and 9.3

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

sofiakavanaugh
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Joined: Thu Jul 13, 2017 3:00 am
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### Comparing 9.1 and 9.3

Hello,

This is a really simple question but 9.1 and 9.3 appear to use the same equation to calculate entropy but one added a negative sign to the equation before doing the calculation and the other didn't? I was just wondering why.

Thanks!

Sammy Thatipelli 1B
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### Re: Comparing 9.1 and 9.3

In question 1, the entropy is referring to that of the surroundings, which means that the rate of entropy generation will be a negative number. But in question 3, the entropy we are calculating is referring to the system's, and when we talk about deltaS of the system, the deltaS is positive

Morgan Baxter 1E
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Joined: Thu Jul 27, 2017 3:00 am

### Re: Comparing 9.1 and 9.3

It is important to remember that q(sys)= -q(surroundings).

Nehal Banik
Posts: 64
Joined: Thu Jul 13, 2017 3:00 am

### Re: Comparing 9.1 and 9.3

It will be negative because you switch the sign in this problem, therefore it makes sense to put it there.