Enthalpy Change Definitions Flashcards
Enthalpy change of reaction
The standard enthalpy of reaction for a chemical reaction is the difference between total reactant and total product molar enthalpies, calculated for substances in their standard states.
Enthalpy change of formation
change of enthalpy during the formation of 1 mole of the substance from its constituent elements in their reference state, with all substances in their standard states.
Enthalpy change of combustion
total energy released as heat when a substance undergoes complete combustion with oxygen under standard conditions.
Enthalpy change of neutralisation
the change in enthalpy that occurs when one equivalent of an acid and a base undergo a neutralization reaction to form water and a salt. It is a special case of the enthalpy of reaction.
Enthalpy change of atomisation
the enthalpy change that accompanies the total separation of all atoms in a chemical substance.
Lattice enthalpy
the energy change upon formation of one mole of a crystalline ionic compound from its constituent ions, which are assumed to initially be in the gaseous state. It is a measure of the cohesive forces that bind ionic solids.
Lattice dissociation enthalpy
the enthalpy change needed to convert 1 mole of solid crystal into its scattered gaseous ions. Lattice dissociation enthalpies are always positive.
First ionisation definition
the energy involved in removing one mole of electrons from one mole of atoms in the gaseous state.
Second ionisation definition
the energy required to remove the outermost, or least bound, electron from a 1+ ion of the element.
First electron affinity
the energy released when 1 mole of gaseous atoms each acquire an electron to form 1 mole of gaseous -1 ions.
Second electron affinity
the energy required to add an electron to each ion in 1 mole of gaseous 1- ions to produce 1 mole of gaseous 2- ions.
Mean bond enthalpy
a measure of bond strength in a chemical bond. IUPAC defines bond energy as the average value of the gas-phase bond-dissociation energy for all bonds of the same type within the same chemical species.
Enthalpy of hydration
the amount of energy released when one mole of ions undergoes hydration.
Enthalpy of solution
the enthalpy change associated with the dissolution of a substance in a solvent at constant pressure resulting in infinite dilution. The enthalpy of solution is most often expressed in kJ/mol at constant temperature.
