## Gibbs Free Energy Equations

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

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

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

Alexia Joseph 2B
Posts: 56
Joined: Thu Jul 27, 2017 3:01 am

### Gibbs Free Energy Equations

Can someone go over a summary of a situation you should use each Gibbs equation in?

Joyce Lee 1C
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Joined: Fri Sep 29, 2017 7:03 am
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### Re: Gibbs Free Energy Equations

Gibbs Free Energy is defined as: G = H -TS
For a process at constant temperature:
ΔG = ΔH - T ΔS or (ΔG-T) = (ΔH/T) - ΔS
At constant temperature and pressure
ΔG = -T ΔStot
To find the Gibbs free energy of reaction, ΔG, using difference in molar Gibbs free energies, Gm
ΔG = ∑nGm (products) - ∑nGm (reactants)
To find standard Gibbs free energy, ΔG°, in terms of standard molar Gibbs energies
ΔG° = ∑nΔG°m (products) - ∑nΔG°m (reactants)
When a system is at equilibrium:
Gp° - Gr° = -RTln([P]/[R]) = -RTln(k)
When the system is not at equilibrium:
ΔG = Gp - Gr = Gp° - Gr° + RTln([P]/[R]) = ΔG° + RTln(Q)

I'm pretty sure there are more that I didn't include...

Michelle Lee 2E
Posts: 64
Joined: Thu Jul 27, 2017 3:01 am

### Re: Gibbs Free Energy Equations

In friday's lecture (and other prior unrelated lectures), Dr. Lavelle set two gibbs free energy equations equal to each other. Can we assume that we can set any of these equations for gibbs free energy equal to each other? (not standard gibbs free energy because that's not the same as just gibbs free energy)

Mishta Stanislaus 1H
Posts: 45
Joined: Fri Sep 29, 2017 7:04 am

### Re: Gibbs Free Energy Equations

Michelle Lee 2E wrote:In friday's lecture (and other prior unrelated lectures), Dr. Lavelle set two gibbs free energy equations equal to each other. Can we assume that we can set any of these equations for gibbs free energy equal to each other? (not standard gibbs free energy because that's not the same as just gibbs free energy)

I have the same question