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Edition 7 number 4F11

Posted: Tue Feb 12, 2019 3:01 pm
by Hedi Zappacosta 1E
"Q4A. During the test of an internal combustion engine, 3.00L of nitrogen gas at 18.5 degrees C was compressed suddenly (and irreversibly) to .500L by driving in a piston. In the process the temperature of the gas increased to 28.1 degrees C. Assume ideal behavior and 1.00 mole of nitrogen gas. What is the change in entropy of the gas?"

I got the answer right, but I was wondering why it was ok for us to ignore the number of moles of N2 gas in this case in the entropy equations.

Re: Edition 7 number 4F11

Posted: Tue Feb 12, 2019 10:37 pm
by Nico Edgar 4L
I am not entirely sure why it was ok to ignore the moles of N2 gas. It might be because we are at ideal conditions and can just assume it is 1? But, in example 4F5 they also ignore the moles and point to the eqaution delta S= C ln(T2/T1). I think it is because we treat the heat capacity as constant in the temperature range.

Re: Edition 7 number 4F11

Posted: Wed Feb 13, 2019 10:54 am
by Nico Edgar 4L
Also I can't seem to get the right answer. Do we find the Entropy change through temperature and then the Entropy change through Volume and sum them?