What is the standard enthalpy of formation?

The standard enthalpy of formation is the change in heat required to form a particular product through a chemical reaction. It is also commonly called the standard heat of formation, and it is represented by the variable delta H or ΔH_f.

The standard enthalpy of formation is found by subtracting the change in heat of reactants from the change in heat of the products, where product refers to the chemicals on the right side of the equation, and reactant refers to those on the left. Commonly used standard enthalpies of formation include -110.5 kilojoules per mole for carbon monoxide, -241.8 kilojoules per mole for water and -393.5 kilojoules per mole for carbon dioxide.