OCR Chemistry A Level Enthalpy Definitions

Standard Conditions

101 kPa, 298K, 1 mol/dm3

Enthalpy change of formation (∆fH)

The enthalpy change when one mole of a substance is formed from its constituent elements in their standard states under standard conditions

Enthalpy of combustion (∆cH)

The enthalpy change when one mole of a substance undergoes complete combustion in oxygen with all substances in their standard states.

Enthalpy of neutralisation (∆neutH)

The enthalpy change when one mole of water is formed in a reaction between an acid and a base under standard conditions

1st Ionisation energy (∆ieH)

The enthalpy change when one mole of gaseous atoms loses one electron to form one mole of -1 gaseous ions.

1st Electron affinity (∆EAH)

The enthalpy change when one mole of gaseous atoms gain one electron to form one mole of gaseous 1+ ions.

Enthalpy of atomisation (∆atmH)

The enthalpy change when one mole of gaseous atoms is produced from an element in its standard state

Hydration enthalpy (∆hydH)

The enthalpy change when one mole of gaseous ions are dissolved in water

Enthalpy of solution (∆solH)

The enthalpy change when one mole of an ionic solid is dissolved in water.

Bond dissociation enthalpy (∆disH)

The enthalpy change when one mole of covalent bonds is broken in the gaseous state.

Lattice enthalpy of formation (∆LEH)

The enthalpy change when one mole of a solid ionic compound is formed from its constituent ions in the gas phase.