## Spontaneity of a reaction

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

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

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

Lauryn Jordan 1F
Posts: 76
Joined: Fri Sep 29, 2017 7:07 am

### Spontaneity of a reaction

In class we discussed rxn or physical change between the change in s and change in h, Dr. Lavelle mentioned that when delta s is negative and delta h is positive it is never spontaneous but the reverse is. does this mean that the reverse of the other 3 would not be spontaneous?

Chem_Mod
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### Re: Spontaneity of a reaction

Hi Lauryn,

Try not to memorize the convention and instead think about the concept. Use the equation$\Delta G = \Delta H - T*\Delta S$ . A reaction will be spontaneous whenever $\Delta G$ < 0. Therefore, it makes sense for a non-spontaneous reaction where $\Delta H$ is positive and $\Delta S$ is negative. Use this equation to figure out the different conditions.

Daniisaacson2F
Posts: 30
Joined: Sat Jul 22, 2017 3:00 am

### Re: Spontaneity of a reaction

I see what you're saying, and I think that it would be easier to just imagine what would make G negative (stated above). But for some of them, the reverse reaction will be the opposite sign of deltaG, changing whether or not it is spontaneous.