Energetics definitions

Standard enthalpy change of reaction

The enthalpy change when the number of moles of reactants as stated in the equation react under standard conditions of 100kPa and 298K.

Standard enthalpy change of formation

The enthalpy change when one mole of a compound is formed from its elements, in their most stable states, under standard conditions of 100kPa and 298K.

Standard enthalpy change of combustion

The enthalpy change when 1 mol of a substance is completely burned in oxygen under standard conditions, all reactants and products being in their standard conditions of 100kPa and 298K.

Standard enthalpy change of neutralisation

The enthalpy change, under standard conditions, when 1 mol of water is produces as a result of the reaction between an acid and an alkali.

Enthalpy change of solution

The enthalpy change when 1 mol of a compound completely dissolves in water under standard conditions.

Enthalpy change of hydration

The enthalpy change when 1 mol of gaseous ions is dissolved in water to form 1 mol of aqueous ions under standard conditions.

Enthalpy change of atomisation

The enthalpy change when 1 mol of gaseous atoms is formed from its element in its standard state.

Lattice enthalpy

The enthalpy change that takes place when 1 mol of an ionic solid is formed from its gaseous ions.

First electron affinity

Energy change that takes place when 1 mol of atoms in the gaseous state gain 1 mol of electrons to form 1 mol of gaseous 1- ions.

First ionisation energy

The energy change that takes place when one electron is lost from each of a mole of atoms in the gaseous state to form one mole of gaseous 1+ ions.

Hess’ Law

If the initial and final conditions are the same, then the total enthalpy change will be the same, regardless of the route taken between reactants and products.

Giant ionic lattice

Opposite charged ions are held together by strong electrostatic forces of attraction in a huge three-dimensional structure.