## What w equation to use

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

Rachel Wang
Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

### What w equation to use

I'm a little confused under what conditions do we use

W = - P x ∆V
or
w = -nRT ln V2

Gwyneth Huynh 1J
Posts: 30
Joined: Fri Sep 29, 2017 7:05 am

### Re: What w equation to use

Use W = - P x ∆V for irreversible expansions (pressure is constant). On the other hand, use W = -nRT ln (V2/V1) or W = -nRT ln (P1/P2) for reversible expansions (pressure is not constant).

704887365
Posts: 49
Joined: Sat Jul 22, 2017 3:00 am

### Re: What w equation to use

Use the first equation for irreversible reactions (constant pressure) and the second for reversible reactions (dynamic pressure)

Kristin Ishaya 1A
Posts: 30
Joined: Fri Sep 29, 2017 7:04 am

### Re: What w equation to use

Was question 4A from the midterm a reversible expansion problem? I didn't know which formula to use so I did it both ways.

Rachel Wang
Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

### Re: What w equation to use

Kristin Ishaya 1A wrote:Was question 4A from the midterm a reversible expansion problem? I didn't know which formula to use so I did it both ways.

I was confused too, actually, but because pressure was constant I think it's w=-PdeltaV

Troy Tavangar 1I
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

### Re: What w equation to use

The first is for irreversible and the second is for reversible.