Main Page | See live article | Alphabetical index The standard enthalpy change of reaction is the enthalpy change that occurs in a system when 1 equivalent 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 equation This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.