Enthalpy changes

• Atomisation Enthalpy (∆at​H)


  The energy required for the formation of a mole of gaseous atoms under standard conditions
• Lattice Enthalpies (∆le​H)


  • Lattice breaking enthalpy: The energy required to break apart an ionic lattice into its constituent ions in a gaseous state under standard conditions
  • Lattice formation enthalpy: The energy required to form an ionic lattice from its constituent ions in a gaseous state under standard conditions
• Enthalpy of Solution (∆sol​H)

  The enthalpy change when one mole of an ionic solid is dissolved in water to infinite dilution so that the ions no longer interact under standard conditions
• Enthalpy of Hydration (∆hyd​H)

  The enthalpy change when one mole of gaseous ions is dissolved in water to form one mole of aqueous ions under standard conditions
• The solubility of ionic compounds changes depending on the balance of lattice breaking enthalpy and the enthalpy of hydration for that substance
• Enthalpy of solution, hydration and lattice enthalpy can all be combined together into a single energy cycle
• Perfect Ionic Model


  • All the ions are perfectly spherical
  • The ions display no covalent character

  
• Covalent character


  Occurs in ions when two joined ions have varying sizes or charges meaning the distribution of charge is not even
• Born-Haber Cycles


  Allow enthalpy changes to be determined which cannot be measured directly
• Enthalpy changes can be combined to produce a Born-Haber cycle