Enthalpy Definitions

Question 1

Enthalpy change of formation

Answer 1

Enthalpy change when 1 mole of a compound is formed from its constituent elements in their standard states under standard conditions

Question 2

Bond dissociation enthalpy

Answer 2

Enthalpy change when all of the bonds of the same type in 1 mole of gaseous molecules are broken.

Question 3

Enthalpy change of atomisation of an element

Answer 3

Enthalpy change when 1 mole of gaseous atoms is formed from an element in its standard state.

Question 4

Enthalpy change of atomisation of a compound

Answer 4

Enthalpy change when 1 mole of a compound in its standard state is converted to gaseous atoms.

Question 5

First ionisation energy

Answer 5

Enthalpy change when 1 mole of gaseous 1+ ions is formed from 1 mole of gaseous atoms by removing 1 mole of electrons

Question 6

First electron affinity

Answer 6

Enthalpy change when 1 mole of gaseous 1- ions is formed from 1 mole of gaseous atoms.

Question 7

Enthalpy change of hydration

Answer 7

Enthalpy change when 1 mole of aqueous ions is formed from 1 mole of gaseous ions

Question 8

Enthalpy change of solution

Answer 8

Enthalpy change when 1 mole of solute is dissolved in enough solvent that no further enthalpy change occurs on further dilution.

Question 9

Lattice enthalpy of formation

Answer 9

Enthalpy change when 1 mole of a solid ionic compound is formed from its gaseous ions under standard conditions

Question 10

Lattice enthalpy of dissociation

Answer 10

Enthalpy change when 1 mole of a solid ionic compound is dissociated completely into its gaseous ions under standard conditions

Question 11

Enthalpy change

Answer 11

Heat energy transferred in a reaction at constant pressure.

Question 12

Mean bond enthalpy

Answer 12

Enthalpy required to break a particular bond over a range of compounds