## Different ways to calculate deltaG

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

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

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

sofiakavanaugh
Posts: 58
Joined: Thu Jul 13, 2017 3:00 am
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### Different ways to calculate deltaG

Hi,

I was wondering if it always will get you the same answer if you calculate deltaG by calculating deltaH(formation) and delta S(formation) and then using deltaG=deltaH-TdeltaS or by using the deltaG based on the deltaG of formation values in the table. Will you always get the same answer? Does it matter which one we use, or does it just depend on what information we are given?

Thanks

DianaTrujillo2K
Posts: 40
Joined: Fri Sep 29, 2017 7:04 am

### Re: Different ways to calculate deltaG

We use an equation to calculate delta G based on the information we are given in the problem.

Aijun Zhang 1D
Posts: 53
Joined: Tue Oct 10, 2017 7:13 am

### Re: Different ways to calculate deltaG

I think the delta G of formation values in the table is just the delta G knot value. It is just the value of a substance in the standard state.
However, delta G can be a value at any state, for example, not 298K or 1 atm.
The result will be the same if the reaction is under the standard state.

Also, there is an equation: $\Delta G = \Delta G^{\circ}+RT\ln Q$

However, if delta H and delta S are all in the standard state. Then the delta G calculated is the standard free energy.

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