Stability

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

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

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

105114680
Posts: 60
Joined: Fri Sep 28, 2018 12:23 am

Stability

I need help thinking through how a raise in temperature affects the stability of compounds with respect to their elements. I know you can use the Gf and Hf of the compound to solve for the -TdeltaSf term in the gibbs free energy equation, and that if T increases than the whole -TdeltaSf term increases but then I get confused with what to do with that information and how to make a claim about stability. Can someone clarify this concept?

805087225
Posts: 30
Joined: Thu Jun 07, 2018 3:00 am

Re: Stability

It all depends first on whether the equation represents an exothermic or endothermic reaction.
If G is negative, it is said to be a spontaneous reaction.

Jessica Chen 1F
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

Re: Stability

If the reaction is exothermic, heat is a product and increasing the temperature would cause the reaction to shift toward the reactant side, making reactants more stable and products less stable.
If the reaction is endothermic, heat is a reactant and increasing the temperature would cause the reaction to shift toward the product side, making products more stable and the reactants less stable.

Lorena Zhang 4E
Posts: 63
Joined: Fri Sep 28, 2018 12:16 am

Re: Stability

For a specific compound, if it's gibbs free energy of formation is negative, then it's relatively stable.