Calculating entropy with changing temperature and volume  [ENDORSED]

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Sabrina Dunbar 1I
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Calculating entropy with changing temperature and volume

Postby Sabrina Dunbar 1I » Tue Feb 13, 2018 10:07 pm

Hi, I am confused about what equation or set of equations to use when you have a problem with changing temperature and volume. An example of this would be from Karen Leung's worksheet titled 2nd and 3rd Laws of Thermodynamics, and it is the last part of question 6.
Another balloon expands from 3.3L at 298K to 9.2 x 105 L at 333K. What is ΔS ? Answer:15.8 J/K
What equations would I use or assumptions would I make in my calculations? Thank you!

Chem_Mod
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Re: Calculating entropy with changing temperature and volume  [ENDORSED]

Postby Chem_Mod » Tue Feb 13, 2018 11:31 pm

To calculate ΔS when more than one variable is being changed, you can simply add different ΔS values: 1 that accounts for the change in temperature, and 1 that accounts for the change in volume. This is because entropy is a state function, so only the final and initial states matter when looking at the change in entropy.

With that being said, look at the constants and equations sheet. Which equation will solve for ΔS when volume is changing? Which equation will solve for ΔS under varying temperature conditions? Once you have found those, apply those equations and add the ΔS values up for the reason I stated above.

Felicia Fong 2G
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Re: Calculating entropy with changing temperature and volume

Postby Felicia Fong 2G » Wed Feb 14, 2018 1:49 pm

Do we solve for n using PV=nrt because moles was not given. Also, C was not given to use in the equation with temp change.


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