11.3 Group II Oxides, Hydroxides and Carbonates

Group II oxides

• All Group II oxides(except beryllium oxide) reacts with water, at least to some extent to give the corresponding hydroxides
• Beryllium oxide is insoluble because Be²⁺ ion is a very small and highly charged ion, thus making the lattice energy of BeO exceptionally high.
• Magnesium oxide is only slightly soluble in water, producing a weakly alkaline solution.
• Addition of calcium oxide with water is a very vigorous and exothermic reaction.
• All Group II oxides(except beryllium oxide) are basic. They react with acids to give the corresponding salt and water
• Beryllium oxide, on the other hand, is amphoteric. It reacts with both acid and base.

Group II hydroxides

• Group II hydroxides are not very soluble, and they do not react with However, the solubility increases down the Group.
• Magnesium hydroxide is only slightly soluble in water, with a pH of about 9.
• Calcium hydroxide(slaked lime) is moderately soluble to give a solution called “lime water”.

• Group II hydroxides behave as a base and react with acids to give the corresponding salt and water

Group II carbonates

• Group II carbonates are mainly insoluble, and they do not react with The solubility decreases down the Group.
• Group II carbonates react with acid to form salt, carbon dioxide and water

MCO3(s) + H⁺ → M²⁺(aq or s) + CO2(g) + H2O(l)   ; where M = A Group  II element