Change in Temperature Equation?

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

Change in Temperature Equation?

Postby Rachel Wang » Sun Jan 28, 2018 5:40 pm

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?

Postby Justin Chu 1G » Sun Jan 28, 2018 6:22 pm

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?

Postby nathansalce 3e » Sun Jan 28, 2018 7:18 pm

^ 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.


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