E740: Equilibrium – Complex Ions – Metal + Ammonia Complexes

Skip to main content Translate English Spanish Chinese French German Korean Lao Nepali Japanese Tibetan

Search

Enter the terms you wish to search for.

Other ways to search:

• Events Calendar
• Campus Map

• Home
• General Reactions
• Quantum
• Molecular Structure
• Gases
• Thermochemistry
• Organic
• Equilibrium
• Electrochemistry
• Kinetics
• Demo List by Class

E740: Equilibrium – Complex Ions – Metal + Ammonia Complexes E740: Equilibrium – Complex Ions – Metal + Ammonia Complexes

Introduction

Ammonia is added to solutions of cobalt, nickel, and copper 2+ cations. First formation of the hydroxide precipitate is seen, then of the ammonia complex.

Co2+ + NH4OH → Co(OH)2(s)	blue ppt. (gives green mixture)
Cu2+ + NH4OH → Cu(OH)2(s)	blue ppt.
Ni2+ + NH4OH → Ni(OH)2(s)	green gel
Co(OH)2(s) + 6NH3 → Co(NH3)62+(aq)	brown complex
Cu(OH)2(s) + 4NH3 → Cu(NH3)42+(aq)	dark blue complex
Ni(OH)2(s) + 6NH3 → Ni(NH3)62+(aq)	blue complex

To Conduct Demonstration

1. Pour 0.1M solutions of Cu2+, Co2+, and Ni2+ into pairs of labeled beakers (to a depth of 1/2") on an overhead projector or document projector, or into 200mm test tubes (to a depth of 1") in a lighted rack.
2. Add 3M or 6M NH4OH drop wise while stirring with the stir rod to one beaker or test tube of each pair. The solutions will become cloudy and change color due to the precipitation of metal hydroxides.
3. Add 15M NH4OH with stirring to the same beaker or test tube. The precipitates will dissolve and darkly colored ammonia complexes will form. (Cobalt requires 6 times the cation volume to form the complex.) Use the other beakers or test tubes as references. Use watch glasses over the beakers or crystallizing dishes to contain the ammonia fumes.

Safety

Ammonia is caustic and irritating to skin, eyes, and the respiratory system.

Acknowledgement:

Stewart Strickler, Spring 1987; Margaret Asirvatham, Fall 1990.

• E710: Complex Ion – Shifting Equilibrium
• E715: Effect of Temperature – NO2/N2O4
• E720: Effect of temperature - [Co(H2O)6]^2+/[CoCl4]^2-
• E730: Complex Ions – Solubility and Complex Ion Equilibria
• E735: Complex Ions and Precipitates – Nickel(II) compounds
• E740: Equilibrium – Complex Ions – Metal + Ammonia Complexes
  • E740: Prep Notes
• E750: Acid Base – pH of Common Household Items
• E755 - Acid/Base - Universal Indicator and Dry Ice
• E760: Acid Base – Amphoterism of Aluminum Hydroxide
• E765: Acid Base – pH Rainbow
• E770: Acid/Base – Common Ion Effect
• E775: Acid Base – Titration
• E780: Acid/Base – Salts as Acids and Bases
• E785: Acid/Base – Effectiveness of a Buffer
• E790: Acid/Base – Conductimetric Titration – Ba(OH)2 + H2SO4