Different ways to calculate deltaG

[sofiakavanaugh]

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]

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

[Aijun Zhang 1D]

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:
This may help you to understand the difference.

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