5.2.1 + 5.2.2 energy

Enthalpy change when 1 mole of a compound is formed from its elements under standard conditions (298k, 100kPa), when reactants and products are in their standard states Na(s) + 1/2 Cl2 (g) > NaCl (s) Exothermic

Enthalpy change when 1 mole of gaseous atoms is formed from the element in its standard state 1/2 O2 (g) > O (g) Na (s) > Na (g) Endothermic

Enthalpy change when 1 mole of a solid metal turns to gaseous atoms Same as atomisation Na (s) > Na (g) Endothermic

Enthalpy change required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous ions with a +1 charge Mg (g) > Mg+ (g) + e-

Enthalpy change required to remove 1 mole of electrons from one mole of gaseous 1+ ions to produce 1 mole of gaseous 2+ ions Mg+ (g) > Mg2+ + e-

Enthalpy change required when 1 mole of gaseous atoms gain 1 mole of electrons to form 1 mole of gaseous ions with a -1 charge Exothermic as ion is more stable than atom, attraction between nucleus and electron O (g) + e- > O- (g)

Enthalpy change required when 1 mole of gaseous -1 ions gain 1 electron per ion to produce -2 ions Endothermic as it takes energy to overcome repulsive forces between negative ion and electron

Enthalpy change when 1 mole of an ionic crystal lattice is formed from its constituent ions in gaseous form Exothermic Na+(g) + Cl- (g) > NaCl (s) Measure of ionic bond strength

Enthalpy change when 1 mole of gaseous ions become aqueous ions Exothermic as bonds made between ions and water molecules

Enthalpy change when 1 mole of an ionic solid dissolves in a large amount of water to ensure that dissolved ions are well separated and don’t interact with one another NaCl (s) + aq > Na+ (aq) + Cl- (aq)

Formation - points Down Atm, ionisation, atm ] - up Ea - points down Lattice enthalpy at end goes down

Size of ions - the larger the ion, the less negative the enthalpies of lattice formation. As ions are larger the charges become further apart so have a weaker attractive force between them Charges on the ion - the bigger the charge, the greater the attraction between ions so stronger the lattice enthalpy (more neg)