Chem Paper 1 Definitions

Relative atomic mass

Average mass of an atom relative to 1/12 the mass of an atom of 12C

Relative molecular mass

Mass of a molecule relative to 1/12 the mass of an atom of 12C

First ionisation energy

Energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions

Standard enthalpy of formation

Enthalpy change when one mole of a compound is formed from its constituent elements with all the reactants and products in standard states under standard conditions

Enthalpy of combustion

Enthalpy change when one mole of a substance is burned completely in excess oxygen with all reactants and products in standard states under standard conditions

Hess’s law

Enthalpy change for a chemical reaction is independent of the route taken

Mean bond enthalpy

Measure of the energy required to break one mole of a covalent bond measured in the gaseous state

Enthalpy of lattice dissociation

Enthalpy change when one mole of an ionic compound is separated into its component gaseous ions

Enthalpy of atomisations

Enthalpy change for formation of one mole of gaseous atoms from the element in its standard states

Bond dissociation

Enthalpy change when one mole of a covalent bond is broken under standard conditions in the gaseous state

First electron affinity

Enthalpy change when one mole of gaseous atoms forms one mole of negative ions with a single negative charge

Buffer solution

Solution that resists changes in pH when small amounts of acid/base are added

Transition metal

Element that has an incomplete d-sub shell in atom/ion state

Ligand

Particle with lone pair of electrons that bonds to metals by dative bond

Complex

Metal ion/atom surrounded by ligands

Coordination number

Number of dative bonds from ligands to metal ions

Heterogeneous catalyst

Catalyst that is in a different phase to the reactants

Homogeneous catalyst

Catalyst that is in the same phase as the reactants

Autocatalyst

The product of the reaction catalysed the reaction