## Equations of delta G

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

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

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

Samantha Chung 4I
Posts: 77
Joined: Wed Oct 03, 2018 12:16 am

### Equations of delta G

How do we distinguish when to use delta G = delta H - delta S temperature and delta G = Delta G (product) - Delta G (reaction)?

Celine Cheng 1H
Posts: 33
Joined: Fri Sep 28, 2018 12:21 am
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### Re: Equations of delta G

Both can give you the same thing, you just need to look at what you're given and determine which formula has it ex. if you're given delta H, T, and delta S, then you'll want to use delta G = delta H - T delta S

Amy Lefley 1J
Posts: 60
Joined: Fri Sep 28, 2018 12:15 am

### Re: Equations of delta G

It is also important to note that you might get slightly different answers when using the two different methods due to rounding differences since you are using a table of information for one and information given in the problem for the other.

Desiree1G
Posts: 62
Joined: Fri Sep 28, 2018 12:16 am
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### Re: Equations of delta G

It is usually based on your givens and if you have enthalpy then most likely the first one will be used. It helps to check off what you have and see what you can plug in.

A De Castro 14B 2H
Posts: 75
Joined: Fri Sep 28, 2018 12:29 am

### Re: Equations of delta G

Don’t forget that there is also this equation: ∆G = ∆G° + RTlnQ A lot of homework questions about Gibbs free energy can only be answered with this. It’s generally used when given a temperature value, a K value, and concentations/partial pressures of reactants and products to calculate Q.

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