Question

Explain the process to obtain the crystals of pure copper sulphate from an impure sample

Answer 1

Crystallization process

The solution is heated in an open container

The solvent molecules start evaporating, leaving behind the solutes

When solution cools, crystals of solute start accumulating on the surface of the solution

Crystals are collected and dried as per the product requirement

The undissolved solids in the liquid are separated by the process of filtration

The size of crystals formed during this process depends on the cooling rate.

Large number of tiny crystals are formed, if the solution is cooled at a fast rate

Large crystals are formed at slow cooling rates



Separation technique of substance by Crystallization

Activity:

Here is an experiment to understand crystallization clearly:

Step 1: Take 50 ml water in a beaker

Step 2: Add sugar in it and stir it

Step 3: Now heat the solution

Step 4: Repeat the process continuously

Step 5: After some time there will be a point at which no more sugar can be dissolved in water. This stage is the saturation point, and the solution is referred as a saturated solution

Step 6 : Now filter the sugar with the help of a filter paper

Step 7: Collect the filtrate in a glass bowl and cool it

Step 8: We will observe that some fine crystals are formed in the bowl

Step 9: The process of filtration can separate these crystals. The liquid left after the removal of crystals is known as mother liquor

in same way it is used for copper sulphate