Thermodynamics

• Enthalpy of formation

  Enthalpy change when one mole of a substance is formed from its constituent elements with all substances in their standard states

  e.g 2Na(s) +1/2 O2 (g) -->Na2O (s)
• Enthalpy of combustion

  Enthalpy change when one mole of a substance undergoes complete combustion in oxygen with all substances in their standard states

  H2(g) +1/2 O2 (g) --> H20 (g)
• Enthalpy of neutralisation

  Enthalpy change when one mole is formed in a reaction between an acid and alkali under standard condition

  1/2 H2SO4 (aq) + NaOH (aq) --> 1/2 Na2SO4 (aq) + H20 (l)
• First ionisation energy

  Enthalpy change when each atom in one mole of gaseous atoms loses one electron to form one mole of gaseous 1+ ions

  Mg (g) --> Mg+ (g) + e-
• Second ionisation energy

  Enthalpy change when each ion in one mole of gaseous 1+ ions gains one electron to form one mole of gaseous 2+ ions

  Mg+ (g) --> Mg 2+ (g) + e-
• First electron affinity

  Enthalpy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous 1- ions

  O (g) + e- -->O- (g)
• Second electron affinity

  Enthalpy change when each ion in one mole of gaseous 1- ions gains one electron to form one mole of gaseous 2- ions

  O- (g) + e- ---> O2- (g)
• Enthalpy of atomisation

  Enthalpy change when one mole of gaseous atoms is produced from an element in its standard states

  1/2 I2 (S) --> I(g)
• Hydration enthalpy

  Enthalpy change when one mole of gaseous ions become hydrated

  Mg 2+ (g) + aq --> Mg 2+ (aq)
• Enthalpy of solution

  Enthalpy change when one mole of an ionic solid dissolves in an amount of water large enough so that the dissolved ions are well separated and do not interact with each other

  MgCl2 (s) + aq --> Mg 2+ (aq) + 2 Cl- (aq)
• Bond dissociation enthalpy

  Enthalpy change when one mole of covalent bonds is broken in the gaseous state

  I2 (g) --> 2I (g)
• Lattice enthalpy of formation

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

  Mg 2+ (g) + 2Cl - (g) ---->MgCl2(s)
• Lattice enthalpy of dissociation

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

  MgCl2 (s) ---> Mg 2+ (g) + 2Cl - (g)
• Enthalpy of vaporisation

  Enthalpy change when one mole of a liquid is turned into a gas

  H20 (l) --> H20 (g)