## Change in Temperature Equation?

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

Rachel Wang
Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

### Change in Temperature Equation?

In Hmwk question 9.7 we used the equation
∆S = n C (ln T2/T1)
but in question 9.13 we use the equation
∆S = n R (ln T2/T1).

When do we know which one to use?
Thanks!

Justin Chu 1G
Posts: 52
Joined: Thu Jul 13, 2017 3:00 am
Been upvoted: 1 time

### Re: Change in Temperature Equation?

Is it simply just due to the difference of a reversible vs irreversible reaction?

nathansalce 3e
Posts: 52
Joined: Thu Jul 27, 2017 3:01 am

### Re: Change in Temperature Equation?

^ Not quite. The change in entropy is a state property, so to calculate entropy would not depend on the path taken to change the entropy. Therefore, it is not a difference of reversible vs irreversible reaction.

R is the gas constant and C is the heat capacity so I believe the difference lies in the temperature dependence that Entropy has in the context of the problem.