## 9.81

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

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

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

Alexa Tabakian 1A
Posts: 38
Joined: Fri Sep 28, 2018 12:20 am

### 9.81

Which is the thermodynamically more stable iron oxide in air, Fe3O4(s) or Fe2O3(s)? Justify your selection.

How do you know, is it based on the molecular mass?

Kristen Kim 2K
Posts: 70
Joined: Fri Sep 28, 2018 12:16 am

### Re: 9.81

The standard values for Gibbs free energy for both of these compounds are in Appendix 2A. We can plug in these values into the products minus reactants formula for Gibbs free energy. Depending on if the delta G is positive or negative, we can determine if the forward or reverse reaction is more stable.

Sophia Ding 1B
Posts: 62
Joined: Fri Sep 28, 2018 12:16 am

### Re: 9.81

I would think of it more in terms of the chemical reaction first; knowing that one will be the reactant and product, and that the reactant will be oxidized with O2, you can deduce the equation and balance it accordingly. Then I would calculate ∆G using the values in Appendix 2A to then see if the forward reaction is spontaneous (negative) or not, to then see which molecule is more strongly favored.