## Work of Expansion and Compression

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

Tiffany Wu 1K
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Joined: Wed Sep 21, 2016 2:56 pm

### Work of Expansion and Compression

Can someone explain the concept of work of expansion and work of compression when the moles of the reactants and products of gas are different?

Chem_Mod
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### Re: Work of Expansion and Compression

Hello Tiffany! I am a little unsure about what you meant by your question, but here is a response that I think you may find useful.

When given a chemical equation, you can find how the number of moles of gas change, and, through the ideal gas law, you can find how the volume changes under constant pressure.

You can find the change in volume this way:

you have your initial state where: PV(i)=n(i)RT (the "i" means initial)
Therefore V(i)=n(i)RT/P for your initial volume

the number of moles of gas change so that: PV(f)=n(f)RT (the "f" means final)
Therefore, V(f)=n(f)RT/P

Lastly, you can find the change in volume and plug in for the work equation. (Remember this is for a constant pressure process)

Julie Barreto 3A
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Joined: Wed Sep 21, 2016 2:56 pm

### Re: Work of Expansion and Compression

in a bomb calorimeter is it true that
Qsystem =-Qcalorimeter

Andrea Medina 1A
Posts: 13
Joined: Wed Sep 21, 2016 2:58 pm

### Re: Work of Expansion and Compression

Should we know the characteristics of a regular calorimeter an a bomb calorimeter?

GabrielaGutierrez2A
Posts: 11
Joined: Wed Sep 21, 2016 2:58 pm

### Re: Work of Expansion and Compression

The course reader, on page 22 says, "since all of thermodynamics is the study of changes in energy for a system at equilibrium..." should we assume that any thermo problem we do will be at equilibrium? If so, is it thermodynamic or chemical equilibrium?