## Problem 9.13 6th edition

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

melissa_dis4K
Posts: 106
Joined: Fri Sep 28, 2018 12:28 am

### Problem 9.13 6th edition

During the test of an internal combustion engine, 3.00 L
of nitrogen gas at 18.5 C was compressed suddenly (and
irreversibly) to 0.500 L by driving in a piston. In the process,
the temperature of the gas increased to 28.1 C. Assume ideal
behavior. What is the change in entropy of the gas?
So I know I have to find the change in entropy from the change in volume and then the one from change in temperature. However, in the solutions manual I see they used 1 mol and I am confused as to how I should know that it is 1 mol? Is it always 1 mol or are we supposed to use pv=nRT to find the nmber moles in which case for this question How would I do that since I am not given pressure or an exact temperature. Or am I supposed to always assume its 1 mol? Thank you

Shubham Rai 2C
Posts: 64
Joined: Fri Sep 28, 2018 12:27 am

### Re: Problem 9.13 6th edition

The key wording of the problem is "assume ideal behavior", this basically states that assume all the unknown values are that of an ideal gas. In this case that would be that the n value is 1 mole.