Question

Salt can be recovered from its solution by evaporation. Suggest some other technique for the same?

Answer 1

Part 1: Evaporation:

• Evaporation is the process of changing a liquid into its vapor state by the action of heat.
• The process of evaporation can be made faster by heating.
• The process of evaporation is used on a large scale to obtain common salt from seawater.
• Sea water is trapped in shallow ponds and allowed to evaporate in the sun.

The other method used to recover the salt from its solution is crystallization. Crystallization is a more efficient process as it removes soluble impurities which cannot be done by evaporation.

Part 2: Crystallization:

• Crystallization is a technique used for the purification of substances.
• It is a separation technique to separate solids from a solution.

Crystallization Process:

• In this process the solution is heated in an open container.
• The solvent molecules start evaporating, leaving behind the solutes in the container.
• When the 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.
• Many tiny crystals are formed if the solution is cooled at a fast rate.
• Large crystals are formed at slow cooling rates.