Preparation of tetraaminecopper(ii) sulphate complex

1. SHREE MALLIKARJUN COLLEGE CLASS:SYBSC
SAFETY: Refer to MSDS of copper sulphate, ammonia, ethyl alcohol
-Dr. Mithil S. FalDesai
Aim: Preparation of tetraaminecopper(II) sulphate complex.
Chemicals: Copper sulphate, ammonium hydroxide, ethyl alcohol.
Apparatus: Measuring cylinder, beakers, funnel and glass rod, filter papers
Theory: In tetraaminecopper(II) sulphate monohydrate, four ammonia ligand binds to the Cu(II)
ion in a tetrahedral fashion.
[Cu(H2O)6]SO4 + 4NH3  [Cu(NH3)4]SO4.H2O + 5H2O
This is a type of ligand substitution reaction as water molecules are replaced by ammonia. The
hexaaquacopper(II) pale blue while the ammonia substituted complex is blue-purple.
Cu can be determined idometrically by decomposing the complex in dilute sulphuric acid.
Procedure:
Weigh about 2.5 g of copper sulphate pentahydrate, and transfer in a 50.0 mL conical flask. Add
a minimum quantity of water to dissolve the copper salt. Add 10.0 mL of concentrated aqueous
ammonia and swirl the solution. To this intense blue colour solution, add 10.0 mL of
ethanol/methanol. Place the conical flask in a water bath with a loosely fitted rubber cork. Heat
the flask containing this suspension until a clear deep blue solution is obtained. If there is a colour
change from deep blue to light blue, add carefully concentrated aqueous ammonia again until a
deep blue coloured solution is just obtained. Immediately, transfer this clear hot solution to a
preheated beaker and leave the beaker covered and undisturbed for one hour. Filter the crystals
and wash the crystals using 2.0 mL of alcohol. Dry the crystals by leaving them on the filter paper
for about an hour. Record the yield of the product.
Results:
i) Amount of tetraaminecopper(II) sulphate formed = _____g.
ii) Percentage yield of tetraaminecopper(II) sulphate obtained =_____%