5.2 Definitions

Question 1

Lattice dissociation enthalpy

Answer 1

The enthalpy change when 1 mol of solid ionic compound is completely dissociated into its constituent gaseous ions under standard conditions

Question 2

Lattice formation enthalpy

Answer 2

The enthalpy change when 1 mol of solid ionic compound is formed from its constituent gaseous ions under standard conditions

Question 3

Atomisation energy

Answer 3

The energy required for the formation of 1 mol of gaseous atoms from an element under standard conditions

Question 4

Enthalpy of electron affinity

Answer 4

The enthalpy change when 1 mol of electrons is added to 1 mol of gaseous atoms to form 1 mol of gaseous 1- ions under standard conditions

Question 5

First ionisation energy

Answer 5

The energy required to remove 1 mol of electrons from 1 mol of gaseous atoms to form 1 mol of gaseous 1+ ions

Question 6

Enthalpy change of hydration

Answer 6

The enthalpy change when 1 mol of a gaseous ion dissolves in water (e.g. Na+(g) –> Na+(aq)

Question 7

Why is there an energy change when dissolving gaseous ions in water?

Answer 7

The polar nature of water stabilises the ions
The greater the charge density of the ion, the greater the affinity for water and the more exothermic the process will be

Question 8

Enthalpy change of a solution

Answer 8

The enthalpy change when 1 mol of a solute dissolves in a solvent (e.g. NaCl(s) –> NaCl(aq)

Question 9

Lattice dissociation enthalpy EXO OR ENDO?

Answer 9

Endothermic (breaking bonds uses energy)

Question 10

Lattice formation enthalpy ENDO OR EXO?

Answer 10

Exothermic (formation of bonds releases energy)