Enthalpy changes from D Hf

1. Enthalpy changes from DHf L.O.: Use enthalpy changes of formations to calculate an enthalpy change of a reaction indirectly.

2. Enthalpy of reaction from enthalpies of formation If you formed the products from their elements you should need the same amounts of every substance as if you formed the reactants from their elements. Enthalpy of formation tends to be an exothermic process