Free Energy Diagrams: Understand Endo/Exothermic Reactions

[lollol]

It's thermo.. so I just posted it in the physics forums

but.. a free energy diagram is supposed to represent G right?

We normally conclude whether a rxn is endo/exothermic depending on whether the product is at a "lower" or higher energy than the reactants just by looking at the diagram

But how can we do that? especially if Delta G = Delta H - (T * Delta S)
Free energy depends on Entropy and Temperature as well

A "negative" change in free energy surely does not necessarily mean an exothermic reaction... but somehow, we are able to conclude whether something is exo/endo simply by looking at a free energy diagram.. how?

 

[russ_watters]

The diagram you have there doesn't have any numbers on it, but if it did it would be valid for only one set of initial conditions.

I'm not sure I understand your last sentence. A negative delta G is exothermic because it means energy is released. The initial hump there doesn't have anything to do with if the final result is exothermic or endothermic - it is just the required activation energy (in this case, it looks like the energy required to disassociate the constituents of the compound).