### change in entropy with change in temperature

Posted:

**Sun Feb 04, 2018 10:43 pm**is deltaS=n*R*ln(T2/T1) or deltaS=n*C*ln(T2/T1)? because the book uses both. Also when do we know which one to use when?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=131&t=26915

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Posted: **Sun Feb 04, 2018 10:43 pm**

is deltaS=n*R*ln(T2/T1) or deltaS=n*C*ln(T2/T1)? because the book uses both. Also when do we know which one to use when?

Posted: **Sun Feb 04, 2018 10:45 pm**

You use the one with R when you have V1/V2. You use the one with C when you have T1/T2.

Posted: **Sun Feb 04, 2018 10:53 pm**

Just adding onto the above post. The first equation is looking at when the change in volume is positive; therefore entropy is increasing. The second one occurs under constant pressure and we are looking at the change in temperature. Here, lower temperature means higher entropy. Hope that helps!