In aqueous solution, the following metal-aqua ions are formed:
M(H2O)62+, limited to M = Fe and Cu
M(H2O)63+, limited to M = Al and Fe
The acidity of M(H2O)63+ is greater than that of M(H2O)62+
Some metal hydroxides show amphoteric character by dissolving in both acids and bases (eg hydroxides of Al3+).
Students should be able to:
- explain, in terms of the charge/size ratio of the metal ion, why the acidity of M(H2O)63+ is greater than that of M(H2O)62+
- describe and explain the simple test-tube reactions of: M2+(aq) ions, limited to M = Fe and Cu, and of M3+(aq) ions, limited to M = Al and Fe, with the bases OH–, NH3 and CO32–