## Problem 9.13

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

Moderators: Chem_Mod, Chem_Admin

Gurvardaan Bal1L
Posts: 54
Joined: Fri Sep 29, 2017 7:04 am
Been upvoted: 2 times

### Problem 9.13

For problem 9.13, why is R used instead of heat capacity for the entropy equation regarding temperature change?

Wayland Leung
Posts: 51
Joined: Sat Jul 22, 2017 3:00 am
Been upvoted: 1 time

### Re: Problem 9.13

Yea i was also wondering why the heat capacity wasn't needed. Would we be wrong if we used the heat capacity?

Nancy Dinh 2J
Posts: 59
Joined: Fri Sep 29, 2017 7:07 am

### Re: Problem 9.13

Gurvardaan Bal1L wrote:For problem 9.13, why is R used instead of heat capacity for the entropy equation regarding temperature change?

Heat capacity by definition is the amount of energy required to raise the temperature of a certain amount of substance by 1 kelvin. In the problem however, you're not raising or lowering the temperature because it is at a constant 85 degrees C. Therefore, you have no use for the formula delta S = n*C* ln(T2/T1), which is what I'm guessing you were thinking of.

Instead, use delta S=n*R*ln(V2/V1). You can see how they derived this equation on page 323.

Cali Rauk1D
Posts: 51
Joined: Fri Sep 29, 2017 7:03 am

### Re: Problem 9.13

how do you know when to change it from T2/T1 to V2/V1?

Christine Wastila 1H
Posts: 61
Joined: Fri Sep 29, 2017 7:04 am

### Re: Problem 9.13

9.13 is listed in the solution manual errors page on the class website. It should be C instead of R for calculating entropy change due to a change in temperature.

Return to “Concepts & Calculations Using Second Law of Thermodynamics”

### Who is online

Users browsing this forum: No registered users and 0 guests