Thermodynamics 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

Question 3

Ionisation enthalpy

Answer 3

The first ionisation energy is the enthalpy change when one mole of gaseous atoms loses one electron per atom to produce gaseous 1+ ions.

The second ionisation energy is when one mole of gaseous 2+ ions is produced from one mole of 1+ ions.

Question 4

Electron affinity

Answer 4

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

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

Question 5

Enthalpy of atomisation

Answer 5

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

Question 6

Hydration enthalpy

Answer 6

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

Question 7

Enthalpy of solution

Answer 7

Enthalpy change when one mole of an 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 8

Bond diss enthalpy

Answer 8

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

Question 9

Lattice enthalpy of formation

Answer 9

Enthalpy change when one mole of a solid ionic compound is formed from into 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