5: Lattice Enthalpy

Question 1

Lattice enthalpy definition

Answer 1

The energy released when one mole of a crystal is formed from its constituent ions in their gaseous state.

Standard conditions of 298K and 101kPa are applied.

E.g. X+(g) + Y-(g) —> X+Y-(s)

Question 2

Enthalpy of atomisation

Answer 2

Enthalpy of atomisation of an element is the enthalpy change when one mole of gaseous atoms is formed from the element in its standard state.

Question 3

Ionisation energy

Answer 3

The energy required to remove one mole of electrons from one mole of gaseous atoms.

Question 4

Electron affinity

Answer 4

The enthalpy change accompanying the gain of 1 mole of electrons by 1 mole of atoms in the gaseous phase.

Question 5

Enthalpy of formation

Answer 5

The enthalpy change when 1 mole of a compound of formed for its constituent elements in their standard states.

Question 6

🔼H lattice enthalpy = ?

Answer 6

🔼H lattice enthalpy = 🔼H of formation — all other values

Question 7

Standard enthalpy change of solution

Answer 7

The enthalpy change that takes place when one mole of an ionic solid dissolves in water

Question 8

Enthalpy change of hydration

Answer 8

The enthalpy change that accompanies a reaction where one mole of a gaseous ion is completely hydrated by water