kaplan/destroyer PE and exothermic

[pistolpete007]

i think im messing up somewhere on the wording....

which of the following has the most exothermic of heat of hydrogenation

a.cyclopropene
b.cycloheptene

explanation says the greater the heat of hydrogenation the greater the PE. The more PE the less stable the molecule is. cyclopentene has the greatest bond strain there least stable...therefore most exothermic

so does this correlate to the the more PE= more Exothermic.....if it does than it seems to contradict destroyer chem 133 where it says if a rxn is exothermic we see a decrease in PE

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[loanne]

Having more PE in the reactants does make the reaction more exothermic, but i think destroyer means that after undergoing the exothermic reaction, any exothermic reaction, you see a decrease in PE, since the energy level is much lower for the more-stable products.