bond energy

[JKLM]

if you have a chemical like C2H4 and you add Br2 to get the change in energy would you have to break every bond and add it up and then subtract something. If you do have to subtract something what would it be. The bond energy of each bond maybe.

[Chemicalsuperfreak]

That's one way to do it. You're also breaking a carbon-carbon double bond, a bromine-bromine bond, and making two carbon-bromine bonds. Everything else remains roughly the same.