Problem with change in temperature and pressure
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Problem with change in temperature and pressure
If you have a chemistry problem where a gas expands in volume AND temperature and were asked to calculate entropy, would you first solve the problem using the equation for two different volumes, and then assume volume is constant and calculate the entropy for two separate temperatures and add them?
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Re: Problem with change in temperature and pressure
Yes I believe so! I remember doing a problem like this in one of the UA sessions and we set entropy equal to -nRTln(V2/V1) + nCln(T2/T1) and just substituted the values given in the problem to solve for entropy. Not exactly sure why we would assume volume Is constant when the temperature changes though.
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Re: Problem with change in temperature and pressure
Yes! You are correct! You have to solve for them each separately, then add them together.
Re: Problem with change in temperature and pressure
I remember doing a problem like this with my TA and that was how we solved it. I think it is because you can think of the heating happening in one step and the expansion happening in another, since enthalpy is one of those propertied that depends on net change and not the path taken.
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Re: Problem with change in temperature and pressure
Yeah, you use both equations, and add the two values together!
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Re: Problem with change in temperature and pressure
I also was wondering this, and the answers help a lot! It's easy to get tripped up on problems like this that involve a change in two different units.
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