H2 Chemistry 13 - Transition Elements: Ligand Exchange and Colour Changes of Copper(II)

What you will learn

• Adding dilute NH3 to pale blue CuSO4 gives a pale blue Cu(OH)2 precipitate, with NH3 acting as a base.
• Excess concentrated NH3 dissolves the precipitate to a deep blue solution by ligand exchange to [Cu(NH3)4(H2O)2]2+.
• Only 4 of the 6 water ligands are replaced; coordination number stays at 6 (4 NH3 plus 2 H2O).