## Finding the change in entropy with volume and temperature

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

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Mara Lockhart 3J
Posts: 53
Joined: Fri Sep 26, 2014 2:02 pm

### Finding the change in entropy with volume and temperature

For problem numer 8.11 in the textbook and Q4.A on the 2010 Winter Midterm (they are the same question), we are asked to calculate the change in entropy of the gas. We are given a situation of a decrease of volume and simultaneously an increase in the heat. This question is regarding nitrogen and in the comments and errors solutions manual of the textbook, N2 is regarded as linear and we use 5/2 R, hover in the solutions for the midterm, N2 is regarded as monoatomic and we use 3/2 R. Which one is correct?

Niharika Reddy 1D
Posts: 127
Joined: Fri Sep 26, 2014 2:02 pm

### Re: Finding the change in entropy with volume and temperatur

Considering N2 is diatomic and linear, I would go with the solutions manual errors document that uses the molar heat capacity at constant volume for a linear molecule: 5/2 R. N2 is not monatomic so it cannot be 3/2 R.

Kevin Goodman 3G
Posts: 14
Joined: Fri Sep 25, 2015 3:00 am

### Re: Finding the change in entropy with volume and temperatur

The book uses 3/2 R because under perfect conditions, diatomic molecules like N2 are considered to be perfect atoms themselves. Look at this previous post, [url]viewtopic.php?f=77&t=3445&p=9002[/url]

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