AQA A-level Chemistry
Thermodynamics definitions
Questions and Answers
Enthalpy of Formation - answerThe enthalpy change when one mole of a compound is
formed from its constituent elements under standard conditions, all reactants and
products are in their standard states.
Enthalpy of Combustion - answerThe enthalpy change when one mole of substance is
burned completely in oxygen under standard conditions, all reactants and products in
their standard states.
Enthalpy of Atomisation - answerThe enthalpy change of the formation of one mole of
gaseous atoms from the element in its standard state under standard conditions.
First Ionisation Energy - answerThe enthalpy change when one mole of gaseous atoms
is converted into a mole of gaseous ions each with a single positive charge.
Second Ionisation Energy - answerThe enthalpy change when 1 electron is removed
from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions.
First Electron Affinity - answerThe enthalpy change when one mole of gaseous atoms is
converted into one mole of gaseous ions each with a single negative charge.
Second Electron Affinity - answerThe enthalpy change when one mole of electrons is
added to one mole of gaseous ions each with a single negative charge to form ions
each with two negative charges.
Lattice Enthalpy of Formation - answerThe enthalpy change when one mole of solid
ionic compound is formed from its gaseous ions.
(This is always negative)
Lattice Enthalpy of Dissociation - answerThe enthalpy change when one mole of solid
ionic compound is dissociated into its gaseous ions.
(This is always positive)
Enthalpy of Hydration - answerThe enthalpy change when water molecules surround
one mole of gaseous ions.
Enthalpy of Solution - answerThe 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 to not interact with each other.
Thermodynamics definitions
Questions and Answers
Enthalpy of Formation - answerThe enthalpy change when one mole of a compound is
formed from its constituent elements under standard conditions, all reactants and
products are in their standard states.
Enthalpy of Combustion - answerThe enthalpy change when one mole of substance is
burned completely in oxygen under standard conditions, all reactants and products in
their standard states.
Enthalpy of Atomisation - answerThe enthalpy change of the formation of one mole of
gaseous atoms from the element in its standard state under standard conditions.
First Ionisation Energy - answerThe enthalpy change when one mole of gaseous atoms
is converted into a mole of gaseous ions each with a single positive charge.
Second Ionisation Energy - answerThe enthalpy change when 1 electron is removed
from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions.
First Electron Affinity - answerThe enthalpy change when one mole of gaseous atoms is
converted into one mole of gaseous ions each with a single negative charge.
Second Electron Affinity - answerThe enthalpy change when one mole of electrons is
added to one mole of gaseous ions each with a single negative charge to form ions
each with two negative charges.
Lattice Enthalpy of Formation - answerThe enthalpy change when one mole of solid
ionic compound is formed from its gaseous ions.
(This is always negative)
Lattice Enthalpy of Dissociation - answerThe enthalpy change when one mole of solid
ionic compound is dissociated into its gaseous ions.
(This is always positive)
Enthalpy of Hydration - answerThe enthalpy change when water molecules surround
one mole of gaseous ions.
Enthalpy of Solution - answerThe 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 to not interact with each other.
