## 9.11 P is inverse of V

$\Delta S = \frac{q_{rev}}{T}$

Jessica Lutz 2E
Posts: 56
Joined: Fri Sep 29, 2017 7:04 am

### 9.11 P is inverse of V

The question states: Calculate the entropy change when the pressure of 1.50 mol Ne(g) is decreased isothermally from 15.0 atm to .500 atm. Assume ideal behavior.

The solutions manual says the equation for this is deltaS=nRln(P1/P2) instead of P2/P1 because "P is the inverse of V for ideal gases". What does this mean and how did we come to that conclusion?

Brigitte Phung 1F
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### Re: 9.11 P is inverse of V

I believe this is referring to the relationship between P and I in the ideal gas law: PV = nRT. If the equations are rearranged as P = nRT/V or V = nRT/P, and n and T are kept constant, you can see that P and V share an inverse relationship. When either P or V goes up, the other one goes up to maintain the equation when n and T are constant. Hope this helps!

MCracchiolo 1C
Posts: 55
Joined: Sat Jul 22, 2017 3:00 am

### Re: 9.11 P is inverse of V

The concept of P is the inverse of V comes from Boyle's Law, "For a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional."

Meaning, P(1)V(1)=P(2)V(2)

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