## Gibb's Energy and Work

$\Delta G^{\circ}= \Delta H^{\circ} - T \Delta S^{\circ}$

$\Delta G^{\circ}= -RT\ln K$

$\Delta G^{\circ}= \sum \Delta G_{f}^{\circ}(products) - \sum \Delta G_{f}^{\circ}(reactants)$

Leah Savage 2F
Posts: 74
Joined: Fri Sep 29, 2017 7:06 am

### Gibb's Energy and Work

Is Gibb's free energy only for nonexpansion work?
What is the relationship between gibb's free energy and work? what kind of system is w=-P(deltaV) for if it's not for reversible/irreversible processes? Irreversible/reversible processes do expansion work, right?

Michelle Chernyak 1J
Posts: 33
Joined: Fri Sep 29, 2017 7:06 am

### Re: Gibb's Energy and Work

w=-PdeltaV applies to the work done in a irreversible expansion and yes both irreversible and reversible processes do expansion work, there are just two different equations used to solve for w.

Austin Ho 1E
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Joined: Fri Sep 29, 2017 7:04 am
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### Re: Gibb's Energy and Work

I don't think Gibb's Free Energy is only for non-expansion work. Both systems with irreversible and reversible processes can do expansion work. In theory, ΔG=wmax, or the maximum amount of work that can be done is ΔG.

In an irreversible expansion, w=-PΔV; pressure is constant while volume changes. This is because we suddenly change pressure, and wait for volume to shift accordingly.

In a reversible expansion, w=-nRTln(V2/V1); temperature is constant while pressure and volume change simultaneously. This is because external pressure is slowly being adjusted to make the changes infinitesimally small, and thus reversible.

Hope this helps.

Susie Lee 2I
Posts: 20
Joined: Fri Sep 29, 2017 7:05 am

### Re: Gibb's Energy and Work

Gibbs Free Energy measures the useful work obtainable from a thermodynamic system at a constant temperature and pressure.

Rishi Khettry 1L
Posts: 29
Joined: Fri Sep 29, 2017 7:05 am

### Re: Gibb's Energy and Work

Gibbs free energy does not apply only to nonexpansion work