General straightforward question about energy diagrams

[tripkramer]

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The y axis seems to always be "potential energy;" some places say that the delta "y" gives us the Gibbs Free Energy Change and some places say it gives us the Enthalpy change. Which is it? I know often they are both spontaneous (-G) and exothermic (-H), but sometimes they are different!

Let's say on the MCAT they give us a diagram and ask what can we know from it, and give spontaneous and exothermic as two options.

Thanks a lot!

 

[milski]

I would expect the Δy to be ΔG unless otherwise stated. As you mentioned, exothermic is not the same as spontaneous, so anything related to activation energy or before/after states will normally be about Gibbs free energy.

 

[tripkramer]

Thank you