How do I calculate bond energies?

Calculating Energy Changes using bond energies?

• So I'm suppose to be using bond energies to calculate energy changes and see if each reaction is Endothermic or Exothermic. Am I even close to being right? 2 c5h12 + 11 o2 ~> 10 co + 12 h2o (exo) h2 + cl2 ~> 2hcl (endo) n2 + 3 h2 ~> 2 nh3 (endo) h2 + o2 ~> h2o2 (endo) 2 h2 + o2 ~> 2 h20 (endo) 2 h2 + co ~> ch3oh (exo)

• Answer:

  Well, you really need a list of bond energies- otherwise you're dealing with complicated equations. I don't know where you're deciding the endo/exo stuff from- but you have to look up the bond energy for each type- ie, C5H12 and multiply it by the # of moles in the equation. Do that for each side and call the right side negative- then add the two sides. If your answer is negative, energy is released- exothermic. If it's positive, endothermic. Hope that helps!