1. Bond Energy: B.E. The Energy Required to Break a Bond
O - H Bond Energy = 467 kJ/mol
Potential Energy
...Strong bond
C - H Bond Energy = 413 kJ/mol
...Weaker bond
B.E.
B.E.

2. Bond Energies: Chemical Reactions
CH4(g) +
2O2(g) 
CO2(g) +
2H2O(g) O H C H O  + + O C O H O
Bonds Broken
(Endothermic)
Bonds Made
(Exothermic)
4 C-H Bonds
@ 413 kJ/mol
4 O-H Bonds
@ 467 kJ/mol
2 O=O Bonds
@ 498 kJ/mol
2 C=O Bonds
@ 799 kJ/mol
Making Bonds Total E.
Breaking Bonds Total E.
= (4  413) + (2  498)
= (4  467) + (2  799)
= kJ/mol
= 2648 kJ/mol

3. Bond Energies: Chemical Reactions + + H O C O C H O O O H H H
Breaking Bonds Total E.
Making Bonds Total E.
= (4  413) + (2  498)
= (4  467) + (2  799)
= 2648 kJ/mol
= kJ/mol
Hcombustion = B.E.reactants B.Eproducts
Hcombustion = kJ/mol kJ/mol
Hcombustion = kJ/mol
(rxn is exothermic)