TO PREPARATION OF COPPER TETRAMMINE COMPLEX {Cu (NH3)4}SO₄.H₂O

Theory

Tetrammine copper (II) can be prepared by adding ammonia to a solution of copper sulphate. when a precipitate of cupric hydroxide in formed which dissolves in excess of ammonia to form a deep blue solution. The hydrated tetrammine copper (II) sulphate is then precipitated from the solution by adding ethyl alcohol because it is insoluble in alcohol.

 

Requirements:

1. Copper sulphate crystals = 5.0 g

2. Concentrated ammonia = 10.0 ml

3. Ethyl alcohol = 30.0 ml.

 

Chemical Equations : CuSO₄ + 4NH₄ + H₂O⟶{Cu (NH3)4}SO₄.H₂O

Procedure:

• Powder well 5.0 g of copper sulphate crystals (CuSO4.5H₂O) and dissolve in a minimum quantity of water (say 20.0 ml) in a 200 ml beaker. Add a few drops of sulphuric acid to get a clear solution.
• Now add 10.0 ml of concentrated ammonia solution slowly and with constant stirring to copper sulphate solution to get a clear dark blue solution. Add more concentrated ammonia in case there is any turbidity.
• Add 20.0 ml. of ethyl alcohol or rectified spirit from the dropping funnel to the beaker so that blue colour is the nearly discharged and purple coloured precipitate of tetrammine copper (II)sulphate separates out.
• Heat the reaction mixture to 60-70° C on a water bath for 10-15 minutes.
• Stop heating and allow the solution to cool. Needle shaped blue crystals of Tetrammine copper (II) sulphate will separate out.
• Separate the crystals by filtration on a buchner funnel under suction. Wash the crystals with ethyl alcohol.
• Dry the crystals in a desiccator. Note the weight of the dry crystals.

Result:

 Colour of crystals = Blue

Shape of crystals = Needle shaped

Yield of crystals = .... g

Expected yield = 4.0 g.

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