Calculate ΔH the combustion of ethane using the given bond dissociation energies: 2 C2H6 + 7 O2 → 4 CO2 + 6 H2O

Question

Calculate ΔH the combustion of ethane using the given bond dissociation energies:

      2 C₂H₆ + 7 O₂ → 4 CO₂ + 6 H₂O

Bond dissociation energies:

           C-C (347 kJ/mol); C-H (413 kJ/mol); O=O (498 kJ/mol; C=O (799 kJ/mol); O-H (467 kJ/mol)

Answer 1

sum of E_bond * number of bonds*moles of reactants - sum of E_bond * number of moles of products = heat of reaction

2(E_C-C) + 2(6)(E_C-H) + 7(E_O=O) - (4)(2)(E_C=0) - 6(2)E_O-H = heat of reaction

The heat of combustion is 1/2 of this because it is written per mole of ethane. (This is why I prefer having a 1 in front of the fuel molecule)