5.2.1: Lattice enthalpy

Question 1

Enthalpy of formation (ΔfHᶿ)

Answer 1

Enthalpy change when one mole of a substance is formed from its constituent elements in their standard states.

Question 2

Enthalpy of combustion

Answer 2

Enthalpy change when one mole of a substance undergoes complete combustion in excess oxygen with all substances in standard states.

Question 3

Enthalpy of neutralisation

Answer 3

Enthalpy change when 1 mole of water is formed in a reaction between acid and alkali under standard conditions.

Question 4

Enthalpy of atomisation

Answer 4

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

Question 5

First electron affinity

Answer 5

Enthalpy change when one mole of gaseous atoms gain 1 electron per atom to form one mole of gaseous 1- ions.

Question 6

Second electron affinity

Answer 6

Enthalpy change when one mole of gaseous 1- ions gain 1 electron per ion to form one mole of gaseous 2- ions.

Question 7

Hydration enthalpy

Answer 7

Enthalpy change when one mole of gaseous ions become hydrated (dissolved in water).

Question 8

Enthalpy of solution

Answer 8

Enthalpy change when one mole of ionic solid dissolves in an amount of water large enough so that the dissolved ions are well separated and do not interact with each other.

Question 9

Bond dissociation enthalpy

Answer 9

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

Question 10

Enthalpy of vaporisation

Answer 10

Enthalpy change when one mole of a liquid is turned into a gas.

Question 11

Enthalpy of fusion

Answer 11

Enthalpy change when one mole of a solid is turned into a liquid.

Question 12

Enthalpy of fusion is

Answer 12

endothermic (+ve)

Question 13

Enthalpy of vaporisation is

Answer 13

endothermic (+ve)

Question 14

Lattice enthalpy of dissociation

Answer 14

Enthalpy change when one mole of a solid ionic compound is broken up into its constituent ions in gas phase.

Question 15

Lattice enthalpy of dissociation is

Answer 15

endothermic (+ve)

Question 16

Lattice enthalpy of formation

Answer 16

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

Question 17

Lattice enthalpy of formation is

Answer 17

exothermic (-ve)

Question 18

Bond dissociation enthalpy is

Answer 18

endothermic (+ve)

Question 19

Enthalpy of formation is

Answer 19

exothermic (-ve) for most substances

Question 20

Enthalpy of combustion is

Answer 20

exothermic (-ve)

Question 21

Enthalpy of neutralisation is

Answer 21

exothermic (-ve)

Question 22

Ionisation enthalpy (both first and second) is

Answer 22

endothermic (+ve)

Question 23

First electron affinity is

Answer 23

exothermic (-ve)

Question 24

Second electron affinity is

Answer 24

endothermic (+ve) as adding -ve to -ve ion

Question 25

Enthalpy of atomisation is

Answer 25

endothermic (+ve)

Question 26

Hydration enthalpy is

Answer 26

exothermic (-ve)

Question 27

Enthalpy of solution is

Answer 27

either exothermic or endothermic; varies

Question 28

Trend in lattice enthalpy

Answer 28

• Lattice enthalpy = strength of ionic bonding; greater magnitude of lattice enthalpy means stronger ionic bonding
• Compounds with smaller ions and/or ions with higher charges ⟶ stronger attractions ⟶ greater lattice enthalpy