## 9.19

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

Rachel Lu_dis1H
Posts: 66
Joined: Fri Sep 29, 2017 7:06 am
Been upvoted: 1 time

### 9.19

How come for the 3rd step you have to cool the water back to 85 degrees Celsius? Will it always be like that for all questions like this one?

Cooper1C
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am

### Re: 9.19

Because entropy is a state function and you know the vaporization at 100 degrees C, to find the standard entropy of vaporization at 85 degrees C you can heat the water to 100 degrees C, vaporize it, then cool it to 85 degrees C. This will give you the standard entropy of vaporization at 85 degrees C.