Question

Salt can be removed from its solution by evaporation. Another technique which can be used for the separation of a salt from its solution is:
A. Centrifugation
B. Sublimation
C. Evaporation
D. Crystallization

Answer 1

We should know how evaporation works and what is separated by evaporation to answer this question. Evaporation separated solid (solute) from the solution by evaporating the liquid (solvent) on heating. Evaporation is used to separate the dissolved solids.

Complete answer :

The centrifugation technique separates the particles from the solution according to their size and shapes. The separation by centrifugation does not depend upon the separation of solvent and solute, so salt removed from its solution by evaporation cannot be separated by centrifugation.
In sublimation, a mixture is heated so the volatile solid evaporates leaving behind the non-volatile solids. The separation by sublimation does not depend upon the separation of solvent and solute, so salt removed from its solution by evaporation cannot be separated by sublimation.
Evaporation is used for the separation of solids from the solution. Soluble solid dissolves in a solvent and forms a solution. On heating the solution, the solvent evaporates and the solid residue is left behind.
Similarly, the solid can be separated by crystallization. Crystallization is similar to evaporation. The solution is heated so the solvent evaporates leaving behind the crystal of the solid. The solid is separated in the form of crystals so the separation is known as crystallization.

Therefore, option (D) crystallization, is correct.

Note: Evaporation and crystallization are used for the separation of solids from solution. The separation depends upon the boiling point of the solvent. The separation by centrifugation depends upon the density and viscosity. The separation also depends upon the speed of the rotor. Sublimation is used for the separation of solids from the mixture. The separation depends upon the vaporization.