Why does barium hydroxide not dissolve (well) in water despite it being ionic?
All ionic compounds ARE NOT WATER SOLUBLE. The solubility of ionic compounds in water is decided by 2 terms 1. crystal lattice enthalpy The energy required to break 1 mole of ionic crystal into the constituent ions in their gaseous staes 2. Hydration enthalpy The energy released when 1 mole of ions are solvated by water. If energy required is less than the energy supplied then the ionic compound will dissolve in water that is Rule for DISSOLOUTION CRYSTAL LATTICE ENTHALPY < hYDRATION ENTHALPY. Hydration enthalpy is qualitatively measured by size of the cation and anion involved. For large charged small ions the hydration enthalpy is very high. Th e crystal lattice enthalpy is measured approximately by looking at the charge on the cation and anion and their relative sizes. For ionic compounds having cations and anion in greater oxidation state (-ve for anion) and comparable sizes the crystal lattice enthalpy is high. barium hydroxide The cation Barium has Less Hydration enthalpy coz of
