Reaction of copper sulfate with ammonia

Just make a solution of copper sulfate and ad some drops of ammonia. Ammonia acts as a base and a beautiful hydroxide precipitates. However, some ammonia replaces water around the copper ion and give a very intens deep blue solute. This is known as ligand exchange reaction. The delicate balans reminds me of the painting “Starry Night” from Van Gogh.
The following reactions takes place in this test tube:

[Cu(H2O)6]²ᶧ + 2NH3 = [Cu(H2O)4(OH)2] + 2NH4ᶧ
[Cu(H2O)6]²ᶧ + 4NH3 = [Cu(NH3)4(H2O)2]²ᶧ + 4H2O

Видео Reaction of copper sulfate with ammonia канала Bert Arissen