If the reaction 2HgO --> 2Hg + O2 is endothermic, which bonds are the strongest?

Question

The bonds between Hg atoms in the solid metal.
The bond between Hg & O.
The bond between O & O.

Answer 1

If you are using bond energies, then
dH = BE reactants - BE products
If dH is + then BE reactants must be > BE products and that means bonds of reactants must be stronger. You have only one substance on the left (reactants) so bonds on Hg-O must be stronger THAN THE SUM OF THE BONDS OF PRODUCTS.
By the way, what have you heard about this process being true with bond energy ONLY for gas reactions?

Answer 2

To emphasize that last point, you may use bond energies to calculate delta H when EVERYTHING IN THE REACTION ARE GASES. If they are not gases the you must add the energy terms to make them gases; i.e., in this gas HgO is a solid and you would need to add the delta H vaporization. Same for Hg liquid. That doesn't mean you can't ESTIMATE delta H this way; it just means that omitting thse extra terms may cause errors. I have seen many posts recently on on this website that ignores this fact. Delta H values from heats of formation are good; delta H values from bond energies are estimates at the best when everything in the reaction are gases and essentially useless if they are not.

Answer 3

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