Question

give conclusion for the experiment of class 11: To prepare the crystals of pure copper sulphate from a given impure sample of blue vitriol

Answer 1

The crystals are transparent and blue in colour and triclinic in shape

Answer 2

The crystals of pure blue color copper sulfate ($CuSO_4.5H_2O$ )

Explanation:

Experiment to prepare crystals of pure Copper Sulfate ( $CuSO_4.5H_2O$) from a given  impure sample of the blue vitriol  is as follows -

Theory  -

1 - Sample + water + few drops of dilute sulfuric acid ( to prevent  hydrolysis of copper sulfate).

2 - Copper sulfate is dissolved and the insoluble  impurities are left over.

3 -The solution is filtered out. The filtrate is concentrated up to the crystallization point and then  cooled.

4 - After cooling, crystals of copper sulfate ($CuSO_4.5H_2O$ ) is filtered out.

Requirements  -

Copper sulfate sample, a beaker, a china dish, a funnel, test tube, a glass rod, an evaporating dish and a policeman

Procedure

Preparation of Solution

• Take about 25-30 ml of water + pinch of the  powdered crude copper sulfate. Stirring the solution and repeating the same additions and stirring until some of it remains undissolved + 2-3 ml of dilute sulfuric acid (making the solution clear that prevents hydrolysis of the copper sulfate)

Formation of crystals

• The solution is filtered out. The filtrate (left in a china dish) is concentrated up to the crystallization point and then  cooled. Heating the solution till it is reduced to about one-third of its original volume. Stir it to avoid the crust formation
• The formation of a crust or tiny  crystals on the glass rod indicates the crystallization point. Now stop  heating.Transferring and cooling the hot saturated solution in the crystallizing dish. On cooling it we will get deep blue crystals of copper sulfate

Separation of Crystals and Drying

• Decant + Wash the crystals with a little ethyl alcohol + water
• Filtered on filter paper

Conclusion -

The crystals of pure blue color copper sulfate ($CuSO_4.5H_2O$ ) are obtained that are transparent.