Reactions of transition metal ions with bases and ligandsEdexcel A-Level Chemistry: Mind map

Exam questions on Reactions of transition metal ions with bases and ligands

1. A student has four separate solutions containing the hexaaqua ions of chromium(III), iron(III), cobalt(II) and copper(II). She adds aqueous sodium hydroxide dropwise to a sample of each solution and then adds an excess.
   Write the ionic equation for the formation of the precipitate when aqueous sodium hydroxide is added to the copper(II) solution, and state the colour of the precipitate.2 marks
2. A student adds aqueous ammonia dropwise, and then in excess, to a pale blue solution of copper(II) sulfate containing [Cu(H₂O)₆]²⁺.
   Write the ionic equation for the ligand exchange reaction that forms the deep blue complex ion from [Cu(H₂O)₆]²⁺ and ammonia, and state the coordination number of copper before and after the reaction.2 marks
3. Hexaaqua complexes of copper(II) and nickel(II) take part in ligand exchange reactions. Concentrated hydrochloric acid is added to a solution of [Cu(H₂O)₆]²⁺, and, separately, excess ethane-1,2-diamine (en), NH₂CH₂CH₂NH₂, is added to a solution of [Ni(H₂O)₆]²⁺.
   Write the equation for the reaction of [Cu(H₂O)₆]²⁺ with concentrated hydrochloric acid and state the colour change. Explain why the coordination number of copper changes.3 marks