Question

How will you separate a mixture containing sand, common salt and sulphur?

Answer 1

Separation of a mixture of sand, common salt i.e.; Sodium chloride $\left(\mathrm{NaCl}\right)$ and Sulphur $\left(\mathrm{S}\right)$:

Step-1: Addition of Carbon disulphide $\left({\mathrm{CS}}_2\right)$ in the mixture

• On adding the mixture containing sand, common salt and sulphur in carbon disulphide, it is observed that the yellow powdered sulphur gets dissolved in it while sand and common salt do not dissolve in carbon disulphide.
• The mixture obtained above is filtered.
• The undissolved substances i.e.; sand and salt are separated from the mixture as residue and the filtrate is obtained.
• The filtrate i.e.; sulphur dissolved in carbon disulphide is subjected to evaporation.
• During evaporation, carbon disulphide evaporates due to its volatile nature and sulphur is obtained in the powdered form.

Step-2: Addition of water to the residue obtained in Step-1

• Water is added to the residue containing sand and common salt.
• Common salt gets dissolved in the water whereas sand does not gets dissolved.
• This solution is filtered off wherein sand is separated as a residue as it is insoluble in water.

Step-3: Evaporation of filtrate obtained in Step-2

• The filtrate obtained in step-2 i.e.; salt dissolved in water is subjected to evaporation.
• On evaporation of water, common salt is left behind and common salt is separated.

Thus, the three components get separated based on their solubilities in the solvent of choice.