AQA A-Level Chemistry - Thermodynamics

Enthalpy Change of Reaction

The number of moles of reactant specified in the balanced equation reacting together

Enthalpy of Formation

The enthalpy change required to form one mole of a substance from its constituent elements under standard conditions in standard states

Enthalpy of Combustion

The enthalpy change required to completely burn one mole of a substance in the presence of oxygen, with all substances in their standard states

First Ionisation Enthalpy

The enthalpy change when one mole of gaseous atoms loses one electron per atom to produce gaseous +1 ions

Second Ionisation Enthalpy

The enthalpy change when one mole of gaseous +2 ions are formed from one mole of +1 ions

First Electron Affinity

The enthalpy change when one mole of gaseous atoms gains one electron per atom to produce gaseous -1 ions

Second Electron Affinity

The enthalpy change when one mole of gaseous -1 ions gains one electron per ion to form gaseous -2 ions

Enthalpy of Atomisation

The enthalpy change when one mole of gaseous atoms are produced from an element in its normal state

Hydration Enthalpy

The enthalpy change when one mole of gaseous ions become hydrated (dissolved in water)

Enthalpy of Solution

The enthalpy change when one mole of an ionic solid dissolves in an amount of water large enough so that the dissolved ions are far apart enough to not interact with one another

Bond Dissociation Enthalpy

The enthalpy change when one mole of covalent bonds are broken in the gaseous state

Lattice Enthalpy of Formation

The enthalpy change when one mole of a solid ionic compound is formed from its constituent ions in the gas phase

Lattice Enthalpy of Dissociation

The enthalpy change when one mole of a solid ionic compound is broken up into its constituent ions in the gas phase

Hess's Law

The sum of energy changes in the clockwise direction is always equal to the energy changes in the anticlockwise direction of a Hess's Cycle

Hess's Cycle

A physical representation of the different pathways by which our desired product can be formed, including the enthalpy of formation and enthalpy of combustion

Born-Haber Cycle

A physical representation of a complete reaction and the numerous stages involved to calculate a enthalpy value

Enthalpy of Formation BHC

The sum of all other enthalpy diagrams in a Born-Haber cycle. This value is always negative

Positive

Are the following values positive of negative?

- Enthalpy of atomisation

- Ionisation enthalpies

- Enthalpy of vapourisation

- Second electron affinity

- Lattice enthalpy of dissociation

Negative

Are the following values positive of negative?

- First electron affinity

- Lattice enthalpy of formation

- Enthalpy change of reaction

M (s) --> M (g)

enthalpy of atomisation of a metal

1/2 X2 --> X (g)

enthalpy of atomisation of a diatomic

Cl2 --> 2 Cl (g)

Bond dissociation enthalpy of chlorine

Na+ (g) + Cl- (g) --> NaCl (s)

Formation lattice enthalpy of sodium chloride

NaCl(s) --> Na+ (g) + Cl- (g)

Dissociation lattice enthalpy of sodium chloride

CH3CH2OH (l) + 3O2 (g) --> 2CO2 (g) + 3H2O (l)

enthalpy of combustion of ethanol

X (g) --> X+ (g) + e-

1st ionisation enthalpy

X+ (g) --> X2+ (g) + e-

2nd ionisation enthalpy

X (g) + e- --> X- (g)

1st electron affinity

X- (g) + e- --> X2- (g)

2nd electron affinity

H2O (l) --> H2O (g)

enthalpy of vaporisation of H2O

H2O (s) --> H2O (l)

enthalpy of fusion of H2O