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

Explanation

Mercury and water are separated by decantation by using separating funnel as the separation of two immiscible liquids by a separating funnel depends 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 a solid changes directly into vapours on heating and vapours change into solid on cooling without going in liquid state.

(c) Common salt, water and sand are separated by
(i) Decantation (or filtration) process is used to separate sand from common salt solution in water because common salt is soluble in water whereas sand is insoluble in water. Therefore, by filtration, sand wil be separated as insoluble substance as residue and filtrate will be common salt solution in water.

(ii) Evaporation process is used to separate common salt from water. Water evaporates and common salt remains as residue.

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