a. Define standard enthalpy change of formation.

b. Calculate the standard enthalpy change of formation of methane from the following standard enthalpy changes of combustion:
carbon = –394 kJ mol^–1
hydrogen = –286 kJ mol^–1
methane = –891 kJ mol^–1

c. Calculate the standard enthalpy change of combustion of methane using the following bond energies:
E(C — H) = +412 kJ mol^–1
E(O — O) = +496 kJ mol^–1
E(C — O) = +805 kJ mol^–1
E(O — H) = +463 kJ mol^–1