Final answer:
The addition of ammonia to a solution of hydrated Cu²+ ions results in the formation of the complex ion: [Cu(NH3)4(H₂O)2]²+.
Step-by-step explanation:
As an example of the formation of complex ions, consider the addition of ammonia to an aqueous solution of the hydrated Cu²+ ion {[Cu(H₂O)]²+}. Because it is a stronger base than H₂O, ammonia replaces the water molecules in the hydrated ion to form the [Cu(NH3)4(H₂O)2]²+ ion. Formation of the [Cu(NH3)4(H₂O)2]²+ complex is accompanied by a dramatic color change, as shown in Figure 16.5.1. The solution changes from the light blue of [Cu(H₂O)]²+ to the blue-violet characteristic of the [Cu(NH3)4(H₂O)2]²+ ion.