Group 2 oxides with water
the oxides of group 2 elements react with water to form alkaline solutions of the metal hydroxides.
hydroxide ions are released, OH-, which make the solutions strongly alkaline.
CaO (s) + H₂O (l) → Ca(OH)₂ (aq)
CaO (s) + H₂O (l) → Ca²⁺ (aq) + 2OHˉ (aq)
the group 2 hydroxides are only slightly soluble in water. when the solution becomes saturated, any further metal & hydroxide ions will form a solid precipitate
Ca²⁺ (aq) + 2OHˉ (aq) → Ca(OH)₂ (s)