9.13

[Emma Ward 2C]

the question states that "during the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5 degrees C was compressed suddenly (and irreversibly) to .500 L by driving in a piston. In the process, the temp of the gas increased to 28.1 degrees C. Assume ideal behavior and 1 mole of Nitrogen gas. What is the entropy of the gas?"

I understand that you can split this problem into two separate entropy problems, one for the change in volume and one with a change in temp because it's a state function. Lavelle identified that this problem is wrong in the solution manual but on his correction on his website, when solving delta S= nCvlnT2/T1, it says that Cv= 5/2R, but on the equation sheet it says Cv= 3/2R for an ideal gas. If someone could just help me see whether I am making a mistake or misunderstanding something or if that was just a typo? thanks!

[Sarah Rutzick 1L]

I believe it is a typo and I would trust the formula sheet.

[Kyle Sheu 1C]

N2 is a diatomic gas and has more degrees of freedom due to greater rotational energy. Cv is 5/2R

[Tia Tomescu 2D]

Page 281 of the textbook gives a good summary of the Cp and Cv for atoms, linear molecules, and nonlinear molecules.