## Substituting -nrT for -PΔV

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

Layal Suboh 1I
Posts: 61
Joined: Fri Sep 28, 2018 12:23 am

### Substituting -nrT for -PΔV

Hello,

When substituting -nrT for -PΔV, how do you know what changing (moles or temperature)?

Jim Brown 14B Lec1
Posts: 62
Joined: Fri Sep 28, 2018 12:28 am

### Re: Substituting -nrT for -PΔV

It will say in the question. Isothermal, same T, moles have to change. Increased Temperature, T changes.

Tatum Keichline 2B
Posts: 64
Joined: Fri Sep 28, 2018 12:26 am

### Re: Substituting -nrT for -PΔV

n and r are constant if T changes, but r and T are constant if the system is isothermal (same temperature)

Dimitri Speron 1C
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Joined: Fri Sep 28, 2018 12:17 am
Been upvoted: 1 time

### Re: Substituting -nrT for -PΔV

You have to balance the chemical equation to see if the number of moles of gas will change. For the temperature the problem will tell you.

Brandon Mo 4K
Posts: 70
Joined: Fri Sep 28, 2018 12:15 am

### Re: Substituting -nrT for -PΔV

The temperature would be given in the problem. To find delta n, you balance the chemical equation and take the difference of moles of gas between the products and reactants.