The combustion of methane is represented by the balanced chemical equation
CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)
Average bond energies (in kJ mol⁻¹) for relevant bonds are listed in the table.
H–C 413 O=O 498 C=O (in CO2) 799 O–H 463
Answer the following prompts. Assume that all species are in the gas phase.
(a) List every distinct bond type that must be broken in the reactants and every distinct bond type that will be formed in the products. Specify the number of each type of bond involved per mole of reaction as written.
(b) Calculate the total energy required to break the reactant bonds.
(c) Calculate the total energy released when the product bonds are formed.
(d) Determine the estimated enthalpy change, ΔH, for the reaction. State its sign and classify the reaction as exothermic or endothermic. Explain how the relative magnitudes of the energies calculated in parts (b) and (c) support your classification.