Problem with change in temperature and pressure

[isha dis3d]

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?

[Jillian Labador 3E]

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.

[Savana Maxfield 3F]

Yes! You are correct! You have to solve for them each separately, then add them together.

[gabbi_r2C]

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.

[Sonel Raj 3I]

Yeah, you use both equations, and add the two values together!

[Jarrett Sung 3B]

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.