Define and explain the enthalpy of combustion `(Delta_(c)H^(theta))`.

Explanation

Standard enthalpy of combustion is defined as the enthalpy change per mole (or per unit amount) of a substance, when it undergoes combustion and all the reactants and products being in their standard states at the specified temperature.
Cooking gas cylinders contains mostly butane `(C_(4) H_(10))`. During complete combustion of one mole of butane, 2658 kJ of heat is released. We can write the thermochemical reaction of this as:
`C_(4)H_(10) +(13)/2 O_(2) (g) to 4CO_(2) (g) +5H_(2)O (1)`
`triangle_(c) H^(theta)="-2658.0 kJ mol"^(-1)`