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 with all elements in standard states.

Question 3

First ionisation energy

Answer 3

The enthalpy change when one mole of gaseous atoms loses one electron per atom to produce gaseous 1+ions.

Question 4

Second ionisation energy

Answer 4

The enthalpy change when one mole of gaseous 2+ ions is produced from one mole of 1+ ions.

Question 5

First electron affinity

Answer 5

The enthalpy change when one mole of gaseous atoms gains one electron per atom to produce gaseous 1-ions.

Question 6

Second electron affinity

Answer 6

The enthalpy change when one mole of gaseous 1- ions gains one electron per ion to produce gaseous 2- ions.

Question 7

Enthalpy of atomisation

Answer 7

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

Question 8

Hydration enthalpy

Answer 8

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

Question 9

Enthalpy of solution

Answer 9

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 10

Bond dissociation enthalpy

Answer 10

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

Question 11

Lattice enthalpy of formation

Answer 11

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

Question 12

Lattice enthalpy of dissociation.

Answer 12

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