Hello,

The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states.

------- Enthalpy of formation can also be considered as a special case of Standard Enthalpy of Reaction.

------ Important thing about Standard Enthalpy of Formation is that it is written for only 1mole of product & the reactants must be in standard state.

I hope you find the answer helpful

Thank you.