How do I calculate enthalpy of combustion?

Calculate the approximate enthalpy change, Delta H(rxn) for the combustion of methane:?

• Calculate the approximate enthalpy change, Delta H(rxn) for the combustion of methane: CH4 + 2O2 ----> 2H2O + CO2 Use the values you calculated in Parts A, B, C, and D, keeping in mind the stoichiometric coefficients.

• Answer:

  It depends on that you have formation standard enthalpy or bonds standard enthalpy which makes me to tell you two answers: 1.use the formation enthalpy method: ΔH=Hf2-Hf1=2Hf H2O + Hf CO2-Hf CH4 2.use the bonds enthalpy method ΔH=Hd1-Hd2=4Hd C-H + 2Hd O=O - 2(2Hd H-O) - 2 C=O