## when to use each equation

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

Eunice Lee 1A
Posts: 60
Joined: Wed Oct 03, 2018 12:16 am

### when to use each equation

When do you use w = -Pex(deltaV) vs. w = -nRTln(V2/V1)?

Nicole Elhosni 2I
Posts: 62
Joined: Fri Sep 28, 2018 12:28 am

### Re: when to use each equation

When pressure is constant (in an irreversible expansion), you will use the first equation w=-pΔV.
When pressure is not constant (in a reversible expansion), you will use the second equation w=-nRTln(V2/V1)

Posts: 35
Joined: Fri Sep 28, 2018 12:19 am

### Re: when to use each equation

An easy way to remember it is that whatever variable is constant is included in the equation.
CONSTANT P: w = -Pex(deltaV)
CONSTANT T: w = -nRTln(V2/V1)?