Video: Colorful copper(II) complexes
Addition of excess chloride ion to the pale blue hexaaquacopper(II) ion gives the green tetrachlorocuprate(II) ion.[Cu(OH2)6]2+(aq) + 4 Cl-(aq) ® [CuCl4]2-(aq) + 6 H2O(l)
Addition of aqueous ammonia (which has a lower density than water) gives a deep blue layer of the hexaamminecopper(II) complex.
[CuCl4]2-(aq) + 6 NH3(aq) ® [Cu(OH2)6]2+(aq) + 4 Cl-(aq)