How to prepare crystals of copper sulphate ?

Aim:

To prepare crystals of copper sulphate.

Aids

  • China dish
  • Glass rod
  • Wash bottle
  • Copper sulphate
  • Burner
  • 250 ml beaker
  • Wire gauze
  • Tripod stand
  • 25 ml water

Method

1. Take a clean beaker (250 ml) and put the powdered impure sample of copper sulphate in it.

2. Add distilled water and stir the contents gently with the help of a glass rod.

3. In order to make the solution more clear add two or three drops of concentrated sulphuric acid in it.

4. Heat the solution in the beaker to 60-700C on a wire gauze.

5. Stir it continuously and add more impure copper sulphate until no more of it dissolves.

6. Filter the solution and collect the filtrate in a china dish.

7. Place the china dish over wire gauze kept over a tripod stand and heat it gently (do not boil).

8. As the solution gets heated, stir it with a glass rod. This helps in uniform evaporation and prevents the formation of a solid crust.

9. When the volume of the solution is reduced to one-half, take out a drop of the concentrated solution on one end of the glass rod and cool it by blowing air. Formation of thin crust indicates that crystallization point is reached.

10. Turn off the burner, cover the dish with a watch glass, and keep it undisturbed. As the solution cools down, crystals separate out. Slow cooling ensures better crystallization.

11. Decant the mother liquor and wash the crystals with a thin stream of cold water with the help of a wash bottle.

12. Dry the crystals by pressing them gently between sheets of filter paper.

Observation

Blue colored crystals of copper sulphate (CuSO4.5H2O) are formed.

Distillation

Distillation is the process of converting a liquid into its vapour state by heating and then cooling the vapour back into the liquid state. The solution to be distilled is taken in a distillation flask and vapours are condensed in the flask with the help of cold water. The liquid, which collects in the flask, is called distillate. Distillate is the purest form of the substance. Distillation is useful in separating the constituents of a mixture.

A Leibig condenser is a modified and better apparatus to use while condensing the vapours.