Is Gibbs energy negative?

1 Answer
Martin M.
May 28, 2017

The change in Gibbs free energy is used to define if a certain reaction takes place spontaneously. You can calculate the change in Gibbs free energy with:

DeltaG=DeltaH-TxxDeltaS

If you have

A negative free energy change
then you calculated the energy remainder, after the spontaneity of the process, that is free to use for other purposes.

A positive free energy change
then you calculated the minimum amount of energy needed to run the process spontaneously.

Remember:
DeltaG<0 color(blue)("Spontaneous")
DeltaG=0 color(blue)("Reversible")
DeltaG>0 color(blue)("Not spontaneous")

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