## Change in Entropy at a Constant Heat Capacity

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

EllerySchlingmann1E
Posts: 76
Joined: Fri Sep 28, 2018 12:24 am

### Change in Entropy at a Constant Heat Capacity

In Topic 4H in the 7th edition of the textbook, it says that "if the heat capacity is constant throughout the temperature range of interest, then
ΔS=nRln(T2/T1)." I was just curious about this equation because I thought for a change in temperature, the appropriate equation to use was ΔS=Cln(T2/T1), and had not seen this equation before, nor saw it discussed in the reading. Any help with explaining the origin of this equation with constant heat capacity would be greatly appreciated. Not sure if I should ignore it or if it supports a fundamental part of thermodynamics. Thanks so much!

Rachel-Weisz3C
Posts: 66
Joined: Fri Sep 28, 2018 12:23 am

### Re: Change in Entropy at a Constant Heat Capacity

I think because the heat capacity is constant the value does not need to be included when solving a problem, therefore you can use the equation they give you for $\Delta$S in order to find entropy, and use the values that should be provided for moles, and the two temperatures.