22.3 Factors affecting lattice enthalpy and hydration

• Lattice enthalpy and enthalpy change of hydration depend on ionic size and ionic charge
• Lattice enthalpy - as ionic size increases

  • attraction between oppositely charged ions decreases
  • lattice enthalpy becomes less exothermic
  • melting point decreases as less energy is required to overcome the increased attraction
• As ionic charge increases

  • attraction between oppositely charged ions increases
  • lattice enthalpy becomes more exothermic
  • melting point increases as more energy is required to overcome the increased attraction
• Hydration enthalpy - as ionic size decreases and ionic charge increases

  • attraction between ion and water molecules increases
  • enthalpy change of hydration becomes more exothermic