Enthalpy Definitions

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Definitions

Standard enthalpy change of combustion

“ Standard enthalpy of combustion is defined as the enthalpy change observed in a constituent thermodynamic system when 1 mole of a substance reacts completely with oxygen under standard conditions. ”

Standard enthalpy change of hydrogenation

“ Standard enthalpy of hydrogenation is the enthalpy change observed in a constituent thermodynamic system, when one mole of an unsaturated compound reacts completely with an excess of hydrogen under standard conditions to form a saturated compound. ”

Standard enthalpy change of formation

“ Standard enthalpy change of formation is defined as the enthalpy change observed in a constituent thermodynamic system when one mole of a compound is formed from its elementary antecedents under standard conditions. ”

Standard enthalpy change of reaction

“ Standard enthalpy change of reaction (denoted H° or Ho) is the enthalpy change that occurs in a system when 1 equivalent of matter is transformed by a chemical reaction under standard conditions. ”

A common standard enthalpy change is the standard enthalpy change 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 change of formation of all of the reactants and products.

Other types of standard enthalpy change include combustion (standard enthalpy change of combustion), neutralisation (standard enthalpy change of neutralisation), melting (standard enthalpy change of fusion), vaporisation/condensation (standard enthalpy change of vaporisation), atomisation (standard enthalpy change of atomisation), mixing (standard enthalpy change of mixing), dissolution (standard enthalpy change of solution), and denaturation (standard enthalpy change of denaturation).