Anhydrous AlCl ₃ is treated with two different aqueous reagents. In the first reaction, it is dissolved in an acidified aqueous solution to form a complex cation P . In the second reaction, it is treated with an excess of aqueous NaOH to form a soluble complex anion Q . The coordination number of aluminium in complexes P and Q , respectively, are:

Step-by-step solution

When AlCl ₃ is dissolved in an acidified aqueous solution, it forms the octahedral hexaaquaaluminium(III) ion, [ Al ( H ₂ O )₆]³⁺ . Thus, the coordination number of aluminium in complex P is 6 . When AlCl ₃ is treated with an excess of aqueous NaOH , aluminium exhibits amphoteric behaviour and forms a soluble tetrahydroxoaluminate(III) complex, [ Al ( OH )₄]^- . In this complex Q , the coordination number of aluminium is 4 . Answer: 6 and 4