Enthalpy Change Definitions

Question 1

enthalpy change of formation (ΔHf)

Answer 1

it is the enthalpy change when one mole of a compound is formed from its constituent elements under standard conditions, all reactants and products in their standards states

Question 2

enthalpy change of atomisation (ΔHat)

Answer 2

it is the enthalpy change which accompanies the formation of one mole of gaseuos atoms from the element under standard states and conditions

Question 3

first ionisation energy (First IE)

Answer 3

standard enthalpy change when one mole of gaseous atoms is converted intoa mole of gaseous ions each with a single positive charge

Question 4

Second ionisation energy (Second IE)

Answer 4

standard enthalpy change when one mole of electrons is lost from a mole of singly charged positive ions

Question 5

First electron affinity (First EA)

Answer 5

standard enthalpy change when a mole of gaseous atoms is converted to a mole of gaseous ions each with a single negative charge

Question 6

Second electron affinity (Second EA)

Answer 6

standard enthalpy change when a mole of electrons is added to a mole of gaseous ioons each with a single charge to form ions with two negative charges

Question 7

Lattice formation enthalpy (ΔHL)

Answer 7

standard enthalpy change when one mole of solid ionic compound is formed from its gaseous ions

Question 8

Enthalpy of hydration (ΔHhyd)

Answer 8

The enthalpy change when one mole of gaseous ions dissolves in water to form an aqueous solution under standard conditions.

Question 9

Enthalpy of solution (ΔHsol)

Answer 9

standard enthalpy change when one mole of solute dissolves completely in sufficient solvent to form a solution in which the molecules or ions are far apart enough not to interact with each other

Question 10

Mean bond enthalpy (ΔHdiss)

Answer 10

Enthalpy change when one mole of gaseous molecules each breaks a covalent bond to form 2 free radicals averaged over a range of compounds