Enthalpy Definitions

Question 1

Enthalpy of atomisation

Answer 1

The enthalpy change which accompanies the formation of one mole of gaseous atoms from the element under its standard state conditions.

Question 2

First ionisation energy

Answer 2

Standard enthalpy change when one mole of gaseous atoms is converted to one mole of gaseous ions each with a single positive charge.

Question 3

Second ionisation energy

Answer 3

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

Question 4

First electron affinity

Answer 4

Standard enthalpy change when a mole of gaseous atoms is converted to a mole of gaseous ion, each with a single negative charge.

Question 5

Second electron affinity

Answer 5

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

Question 6

Lattice formation enthalpy

Answer 6

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

Question 7

Lattice dissociation

Answer 7

Standard enthalpy change when one mole of solid ionic compound separates into its gaseous ions.

Question 8

Hydration

Answer 8

Standard enthalpy change when water molecules surround one mole of gaseous ions.

Question 9

Solution

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

Answer 10

Enthalpy change when one mole of gaseous molecules each breaks a covalent bond averaged over a range of compounds.

Question 11

Enthalpy of formation

Answer 11

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