Enthalpy Definitions

• Lattice enthalpy 


  enthalpy change when 1 mol of solid is formed by coming together of separate gaseous ions under standard conditions
• Lattice enthalpy is always exothermic
• Enthalpy change of hydration

  enthalpy change when solution of ions is formed from 1 mol of gaseous ions
• Enthalpy of formation


  enthalpy change when 1 mol of compound is formed from its constituent elements in their standard states under standard conditions
• Standard conditions


  100 kPa

  298 K

  solutions at 1 mol dm-3
• Enthalpy of combustion


  Enthalpy change when 1 mol of substance is burned in standard state in excess oxygen under standard conditions
• Enthalpy of neutralisation 


  Enthalpy change when 1 mole of water is formed in reaction between acid and alkali under standard conditions