Get premium membership and access revision papers with marking schemes, video lessons and live classes.

Processing. Please wait.

How evaporation is used in separation of mixtures and its applications

Answer Text:
Evaporation.
- Is used to separate a soluble solid from its solution.
- Such solutions are usually homogenous mixtures.
- The solid is called a solute while the liquid is called a solvent.
Example: separation of salt from salt solution.
(i). Procedure:
- The salt solution is poured in an evaporating dish.
- The set-up is then arranged as in the apparatus shown below.
- The solution is boiled under steam or sand bath until all the water in the salt solution evaporates and salt crystals remain in the dish.
(ii). Apparatus.

(iii). Observations and explanations.
- Upon heating the solution, water evaporates because it has lower boiling point than the salt.
- The solution is boiled until salt crystals start appearing on a glass rid dipped into the solution.
- This shall indicate that the solution is saturated.
- The saturated solution is allowed to cool and crystallize.
- The mother liquor (liquid that remains with the crystals) is poured and the salt (solid) dried between absorbent papers.
Note:
A crystal: is a solid that consists of particles arranged in an orderly repetitive manner.
- It is advantageous to boil the solution under a steam or sand bath rather than directly.
Reason:
- The steam or sand bath prevents the mixture from splashing out (spitting) of the evaporating dish.
- It also reduces chances of the evaporating dish cracking.
Applications of evaporation:
- Extraction of soda ash from Lake Magadi