Question

Question 10
Suggest separation technique(s) one would need to employ to separate the following mixtures.

(a) Mercury and water
(b) Potassium chloride and ammonium chloride
(c) Common salt, water and sand
(d) Kerosene oil, water and salt

Answer 1

(a) Mercury and water are separated by decantation by using a separating funnel.The separation of two immiscible liquids by a separating funnel depend on the difference in their densities. Mercury is heavier than water, therefore, forms the lower layer and separated from water.

(b) Potassium chloride and ammonium chloride are separated by sublimation method because ammonium chloride being a sublimate, sublimes leaving behind the potassium chloride. Sublimation is the process in which solid changes directly into vapours on heating and vapours change into solid on cooling without going through the liquid state.

(c) Common salt, water and sand are separated by:
(i) Decantation (or filtration) process is used to separate sand from common salt and water because common salt is soluble in water whereas sand is insoluble in water. Therefore, by filtration; sand will be separated as insoluble substance as residue and filtrate will be the common salt solution in water.
(ii) The evaporation process is used to separate common salt from water. Water evaporates and common salt remains as the residue.

(d) (i) Decantation using separating funnel is used to separate kerosene oil from salt and water solution as they form separate layers (salt is soluble in water).
(ii) Evaporation is used to separate salt from water.