Heat Of Formation (2 Min) - molar enthalpy of formation, enthalpy of reaction 

The heat of formation is the amount of energy released or absorbed (also known as the enthalpy change) when one mol of a substance is formed from its elements at standard atmospheric temperature and pressure (100 kph and 25 degrees celsius). By adding the sum of this formation energy either through calculation or looking for it on a formation data table for the products, and adding the sum of this formation energy for the reactants, by subtracting the two and finding the difference will tell us the amount of heat gained or lost as a whole in the reaction. This final answer is also known as the enthalpy of reaction or delta H reaction that we are familiar with by now.