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The standard enthalpy of reaction (denoted Δr''H''⊖) 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 :−''v''A A + −''v''B B + ... → ''v''P P + ''v''Q Q ... the standard enthalpy of reaction Δ''H''r⊖ is related to the standard enthalpy of formation Δ''H''fo of the reactants and products by the following equation: In this equation, ''vB'' is the stoichiometric number of entity B. A similar enthalpy change is the standard enthalpy of formation, which has been determined for a vast number of substances. The enthalpy change of any reaction under any conditions can be computed, given the standard enthalpy of formation of the reactants and products. It is defined as the amount of heat absorbed or evolved in the transformation of the reactants at a given temperature and pressure into the products at the same temperature and pressure. Enthalpy of a reaction at constant pressure and at a constant volume: Enthalpy of a reaction depends upon the conditions under which the reaction is carried out. There are two general conditions under which Thermochemical measurements are made. (a) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Standard enthalpy of reaction」の詳細全文を読む スポンサード リンク
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