### Calculating Gibbs Free Energy

Posted:

**Wed Mar 14, 2018 10:31 am**How do we know when to do the difference of sums vs when to use the equation to solve for gibbs free energy?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=135&t=29702

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Posted: **Wed Mar 14, 2018 10:31 am**

How do we know when to do the difference of sums vs when to use the equation to solve for gibbs free energy?

Posted: **Wed Mar 14, 2018 11:05 am**

You use difference of sums to find Gibbs free energy when you are using the Gibbs free energy of formation for the reactants and products. If you are given entropy, enthalpy, and temperature, then you would use deltaG=deltaH - TdeltaS.

Posted: **Wed Mar 14, 2018 11:47 am**

Usually i look at what information is given and then am able to determine which equation works.

Posted: **Fri Mar 16, 2018 1:06 am**

Use difference of sums when the information given pertains to the Gibbs free energy of products or reactants, and the other equation when given entropy and enthalpy. Determine what information the question gives you and then you can choose an equation to plug into accordingly

Posted: **Sat Mar 17, 2018 6:39 pm**

It all depends on what is available to you and then with that, you'd be able to decide what to use. But there's usually a chemical equation or steps when it's a difference of sums situation.