The standard enthalpy change of reaction (denoted ΔH° or ΔHo) is the enthalpy change that occurs in a system when one mole of matter is transformed by a chemical reaction under standard conditions.
For a generic chemical reaction
nA A + nB B + ... → nP P + nQ Q ...
the standard enthalpy change of reaction ΔHr is related with the standard enthalpy change of formation ΔHf of the reactants and products by the following equation:
\DeltaHr=\sumproducts{ni\DeltaH
| (i) | |
| f |