## 6th ed 9.65 stability

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

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

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

Celine Cheng 1H
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### 6th ed 9.65 stability

Since we're trying to see which compound is less stable with respect to their elements as the temperature is raised, we would want to see which one has a negative delta S (because that would result in delta G being positive, formation of compound is unfavorable compared to elements)

I had manipulated the Gibbs Free Energy Eqn to
delta S = delta H - delta G (I cancelled out T because it would be the same in all cases)
and I used the enthalpy of formation and gibbs free energy of formation from Appendix 2A

Would this method also work compared to the solutions manual, which calculates delta S using the molar entropies of the reactants and products? Or is that that because it is with respect to their elements, the latter method must be used?

Chem_Mod
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### Re: 6th ed 9.65 stability

$T\Delta S_f = \Delta H_f- \Delta G_f$ can be used to find the sign of $\Delta S_f$ (since T is always positive in this class) instead of using the molar entropies of reactants and products.