Since Al3+ ion is highly charged and quite small the bond uniting the hydrogen and oxygen atoms with coordinated H2O molecules is considerable weakened and other solvent water molecules are able to act as bases and abstract protons[Al(H2O)6]3+(aq.)+H2O(ι)→[Al(H2O)5(OH)]2+(aq.)+H3O+(aq.)[Al(H2O)5OH]2+(aq.)+H2O(ι)→[Al(H2O)4(OH)2]+(aq.)+H3O+(aq.)If the solution also contains a strongly basic anion such as CO2−3orS2− further ionization of hydrated aluminium ions can occur[Al(H2O)4(OH)2]+(aq.)+CO2−3(aq.)⇌[Al(H2O)3(OH)3](solid)+HCO−3(aq.)Behaviour of the cation in CO2−3 solution in the above passage can be considered as: