## Midterm 2013 Q4A

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

anatorres1B
Posts: 13
Joined: Wed Nov 18, 2015 3:00 am

### Midterm 2013 Q4A

To calculate the work from B to C, it appears a variation of the work equation was used. Instead of volume, pressure values were used instead. Why is pressure used instead of the volume? They both change, so how would I go about determining which variation of the work equation to use? Also, in the solution it appears that the equation is w= -nRTln(p1/p2) why are the pressure values not the other way around (p2/p1)??

anatorres1B
Posts: 13
Joined: Wed Nov 18, 2015 3:00 am

### Re: Midterm 2013 Q4A

Also, is it still possible to use the volume variation instead? I used it the first time around and came out with the same answer.

Marie_Bae_3M
Posts: 25
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Midterm 2013 Q4A

Yes, I believe you can use either one. w=-nRTln(p1/p2) is basically found from the original w=-nRTln(v2/v1). This goes back to boyle's law p1v1=p2v2. In other words, v2/v1=p1/p2 (pressure and volume are inversely related to each other) and you plug this into the original equation.

anatorres1B
Posts: 13
Joined: Wed Nov 18, 2015 3:00 am

### Re: Midterm 2013 Q4A

Thank you so much!

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