Which is more stable: Fe3O4 or Fe2O3?

[manasa933]

The solutions manual says Fe2O3 is more stable, but since the G of formation is more negative for Fe3O4 , isn't it more stable? Also since Fe3O4 is a larger compound, shouldn't it be more stable?

[Emily Mei 1B]

Not sure what you mean by "stable", but larger compounds are typically heavier, which means they'd have a larger degeneracy and therefore more entropy. So Fe3O4 should have a higher entropy.

[Elizabeth Ignacio 1C]

I believe the stability of Fe₃O₄ and Fe₂O₃ were mentioned in problem 9.81, and in that problem, it was important to write out the equation that involves the two of them, which is 4Fe₃O₄ + O2 -> 6Fe₂O₃. This Gibbs Free Energy for this forward reaction is negative and the reverse is positive, which means that the reaction that forms Fe₂O₃ is favorable and Fe₂O₃ is more stable.