Different Work Equations

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

chrisavalos-2L
Posts: 63
Joined: Fri Sep 28, 2018 12:18 am

Different Work Equations

I was wondering how to know which of the different work equations that we are to use for different situations?

Catly Do 2E
Posts: 64
Joined: Fri Sep 28, 2018 12:24 am

Re: Different Work Equations

Le learned this in discussion today and these are from my notes!
- For a reversible, isothermal expansion of an ideal gas:
w=-nRTln(Vfinal/Vinitial) OR w=-nRTln(Pinitial/Pfinal)
- For constant pressure:
w=-PdeltaV=-deltanRT
- For constant volume:
w=0

Brian Chhoy 4I
Posts: 66
Joined: Fri Sep 28, 2018 12:16 am

Re: Different Work Equations

It should let you know in the problem. If they are asking for the work done in an isothermal expansion (constant temperature), you probably have to solve for the reversible pathway, since the work the system is doing if being provided energy by some outside source, such as a heat reservoir. If the question is asking for a reaction done against constant pressure, then you would solve for the irreversible pathway.