## Question on Calculating Entropy of Vaporization

$\Delta S = \frac{q_{rev}}{T}$

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Nathan Sanchez 1F
Posts: 12
Joined: Sat Jul 09, 2016 3:00 am

### Question on Calculating Entropy of Vaporization

In example 9.6 when calculating the entropy of vaporization at temperatures other than the normal boiling point, the molar heat capacity at constant pressure for acetone vapor used in the problem is 4R (about 33 J/Kmol). However, when I look up the value in a data table, it is about 75 J/Kmol. I also found that in Self-Test 9.9A, the molar heat capacity at constant pressure of ethanol vapor is given, but 4R is used to get the correct answer. What is going on here?

vsyacoubian2A
Posts: 63
Joined: Fri Jul 22, 2016 3:00 am

### Re: Question on Calculating Entropy of Vaporization

There are different R values depending on the units. Double check what kind of R you are using.

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