Enthalpy definitions

Question 1

Enthalpy of formation

Answer 1

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

Question 2

Enthalpy of combustion

Answer 2

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

Question 3

Enthalpy of neutralisation

Answer 3

Enthalpy change when one mole of water is formed in a reaction between an acid and an 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 ionisation enthalpy

Answer 5

Enthalpy change when each atom in one mole of gaseous atoms loses one electron to form one mole of gaseous 1+ ions

Question 6

Second ionisation enthalpy

Answer 6

Enthalpy change when each ion in one mole of gaseous 1+ ions loses one electron to form one mole of gaseous 2+ ions

Question 7

First electron affinity

Answer 7

Enthalpy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous 1- ions

Question 8

Second electron affinity

Answer 8

Enthalpy change when each ion in one mole of gaseous 1- ions gains one electron to form one mole of gaseous 2- ions

Question 9

Lattice enthalpy of formation

Answer 9

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

Question 10

Lattice enthalpy of dissociation

Answer 10

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

Question 11

Bond dissociation enthalpy

Answer 11

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

Question 12

Hydration enthalpy

Answer 12

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

Question 13

Enthalpy of solution

Answer 13

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 14

Enthalpy of vapourisation

Answer 14

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

Question 15

Enthalpy of fusion

Answer 15

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

Question 16

Enthalpy change

Answer 16

Heat energy transferred in a reaction at constant pressure