## 4F.17

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

Ellis Song 4I
Posts: 102
Joined: Thu Jul 11, 2019 12:17 am

### 4F.17

Calculate the standard entropy of vaporization of water at 85 C, given that its standard entropy of vaporization at 100 C is 109.0 J/Kmol and the molar heat capacities at constant pressure of liquid water and water vapor are 75.3 J/Kmol and 33.6 J/Kmol, respectively, in this range.

I don't know where to begin with this problem and what equations to use!

ALegala_2I
Posts: 102
Joined: Thu Jul 11, 2019 12:17 am

### Re: 4F.17

You have to use the deltaS = nCln(T2/T1) equation. First, you use this equation to raise the temperature of water from 85 - 100 (make sure you convert to Kelvin) and use the molar heat capacities at constant pressure of liquid water. Then, you use this equation to lower the temperature of water from 100 - 85 (make sure you convert to Kelvin) and use the molar heat capacities at constant pressure of water vapor. You add the two entropies and 109.0 J/Kmol to get your answer.