### Gibb's Free energy

Posted:

**Sun Feb 17, 2019 1:04 pm**When is deltaG negative and positive? What's the significance?

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=135&t=42306

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Posted: **Sun Feb 17, 2019 1:04 pm**

When is deltaG negative and positive? What's the significance?

Posted: **Sun Feb 17, 2019 1:08 pm**

When delta G is negative, this signifies that a reaction will proceed spontaneously. If delta G is postive, this means that the reverse reaction will be spontaneous and the forward reaction will be non spontaneous. Delta G is guaranteed to be negative when delta H is negative and delta S is positive. If itâ€™s the reverse (delta S is negative and delta H is positive), then the value of delta G will be positive. When the signs of delta H and delta S are the same, then the sign of delta G will be dependent on the temperature

Posted: **Sun Feb 17, 2019 4:49 pm**

Use the Gibb's Free Energy equation to determine spontaneity. While is is usually true that delta G follows the sign for delta H, please do not use this as a rule of thumb.

Posted: **Sun Feb 17, 2019 5:54 pm**

Delta G is spontaneity. From what I understand is if delta G is spontaneous it is also endothermic and if delta G is negative it is not spontaneous and it is exothermic.

Posted: **Sun Feb 17, 2019 6:57 pm**

delta g represents the spontaneity, so if it is negative it will be spontaneous and if positive it will be non-spontaneous.