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## Homework Statement

A sample of 1.00 mol of an ideal diatomic gas, initially at pressure P and volume V, expands until it has a pressure of 2P and a volume of 2V. What's the entropy change in the gas on this process?

## Homework Equations

2nd Maxwell relation:

4th Maxwell relation:

PV = nRT

## The Attempt at a Solution

[tex]\frac{\partial S}{\partial V}= \frac{nR}{V}[/tex]

[tex]\frac{\partial S}{\partial P} = -\frac{nR}{P}[/tex]

I found out S by doing the standard procedure: integrating the first one and deriving in relation to P to find the function in relation to P. The expression for S i found was:

[tex]S=nR(lnV-lnP)[/tex]

But the variation of S is always 0 this way, and that's not the solution...