Ammines

Summary

Ammine complexes of 2+ ions of copper, nickel and cobalt are made by the addition of ammonium hydroxide. The distinct color of the different metal ammines are observed.

Hazards

• Conc. ammonium hydroxide is toxic and corrosive. Avoid exposure.
• Nickel salts are considered possible carcinogens. Use care.

Chemicals and Solutions

• Conc. Ammonium hydroxide
• 0.1M Copper sulfate
• 0.1M Nickel nitrate
• 0.1M Cobalt chloride

Materials

• 3 hydrometer cylinders
• 3 stir rods

Procedure

Add approximately 2 parts of ammonium hydroxide to each of the metal ion solutions to generate the ammine.

Discussion

$\underset{\text{super blue}}{\mathrm{Cu}{\phantom{A}}^{2+}{\phantom{A}}_{(\mathrm{aq})}+4\mathrm{NH}{\phantom{A}}_3{\phantom{A}}_{(\mathrm{aq})}⟶\mathrm{Cu}(\mathrm{NH}{\phantom{A}}_3){\phantom{A}}_4{\phantom{A}}^{2+}{\phantom{A}}_{(\mathrm{aq})}}$

$\underset{\text{violet}}{\mathrm{Ni}{\phantom{A}}^{2+}{\phantom{A}}_{(\mathrm{aq})}+6\mathrm{NH}{\phantom{A}}_3{\phantom{A}}_{(\mathrm{aq})}⟶\mathrm{Ni}(\mathrm{NH}{\phantom{A}}_3){\phantom{A}}_6{\phantom{A}}^{2+}{\phantom{A}}_{(\mathrm{aq})}}$

$\underset{\text{red/orange}}{\mathrm{Co}{\phantom{A}}^{2+}{\phantom{A}}_{(\mathrm{aq})}+6\mathrm{NH}{\phantom{A}}_3{\phantom{A}}_{(\mathrm{aq})}⟶\mathrm{Co}(\mathrm{NH}{\phantom{A}}_3){\phantom{A}}_6{\phantom{A}}^{2+}{\phantom{A}}_{(\mathrm{aq})}}$