What are the differences between standard enthalpy change of formation and standard enthalpy change of combustion? With examples pls (such as the diffences when drawing Hess's Law cycle)

Asked on by jm244

1 Answer | Add Yours

llltkl's profile pic

llltkl | College Teacher | (Level 3) Valedictorian

Posted on

Standard enthalpy change of formation is the energy change accompanied with the formation of one mole of a compound from the constituent elements, with all substances in their standard states. For example, standard enthalpy of formation of methane, C(s) + 2H2(g) → CH4(g); ΔH0 = -74.78 kJ mol–1. On the other hand, standard enthalpy change of combustion is the enthalpy change when one mole of a reactant completely burns in oxygen under standard thermodynamic conditions. E.g. ΔH0(C) Methane = -890.3 kJ mol−1

CH4(g) + 2O2(g) → CO2(g) + 2H2O; ΔH0 = -890.3 kJ mol–1


We’ve answered 319,865 questions. We can answer yours, too.

Ask a question