(i) The complex `[PtCl_2(NH_3)_2]` has two isomers whereas `[CoCl_4]^(2-)` does not show geometrical isomerism and has no isomers why?
(ii) When NaOH solution is added to aqueous copper (II) sulphate solution, hydroxide ions displace water molecules forming a pale blue precipitate, X. If excess ammonia is now added, water molecules and hydroxide ions are exchanged by ammonia molecules, forming a deep blue solution, Y. Identify X and Y.