Elements, Compounds and Mixtures — Question 2

(a) Sublimation can be used to separate Ammonium chloride from a mixture of ammonium chloride and potassium chloride.

Process — Take a mixture of ammonium chloride and potassium chloride in an evaporating dish, covered with a funnel plugged with cotton. Heat it slowly as shown below:

Ammonium chloride collects on the inner side of the funnel and is scrapped out easily.

Potassium chloride remains in the evaporating dish and is separated out easily.

(b) Magnetic separation can be used to separate iron from a mixture of iron & copper.

Process — Take a mixture of iron & copper in a flat dish. Move a magnet over the mixture as shown below:

Magnetic solid 'Iron' is attracted to the magnet.

Non-magnetic solid 'copper' remains in the dish.

(c) Solvent extraction can be used to separate Sulphur from a mixture of sulphur & copper

Process — Add the mixture to a beaker containing the solvent carbon disulphide. Stir well till sulphur dissolves. Filter the contents.

Soluble component [sulphur] is obtained on slow evaporation of the filtered solution.

Insoluble component [copper] remains on the filter paper.

(d) Fractional crystallization can be used to separate potassium nitrate from a mixture of potassium nitrate & potassium chlorate.

Process — Add the mixture of potassium nitrate & potassium chlorate to a beaker of water & heat to obtain, hot saturated soln. Cool the hot saturated soln. when crystals of less soluble 'potassium chlorate' crystallize out.

Less soluble [potassium chlorate] is filtered out from the hot saturated soln. recrystallized from hot water and dried.

More soluble [potassium nitrate] is obtained from the filtrate by heating the filtrate followed by cooling. The crystals of the more soluble solid crystallize out.

(e) Filtration can be used to separate insoluble lead carbonate from a mixture of lead carbonate & water.

Process — Place a wet folded filter paper in a funnel, clamped above a beaker. Pour the mixture carefully through it.

Insoluble lead carbonate remains on filter paper, it is dried and recovered.

Water remains in the beaker.

(f) Distillation can be used to separate lead nitrate [soluble] from a mixture of lead nitrate & water i.e lead nitrate solution.

Process — Add the mixture to the flask 'X' of the distillation apparatus. The flask is then carefully heated and the mixture evaporates and later condenses.

Soluble lead nitrate remains in the flask 'X' after evaporation.

Water collects in receiver after condensation.

(g) Separating funnel can be used to separate carbon tetrachloride from a mixture of carbon tetrachloride [heavier component] & water.

Process — Pour the mixture from the top of a separating funnel and allow the mixture to stand till the heavier layer [carbon tetrachloride] and lighter layer [water] separate.

Water remains in the separating funnel and carbon tetrachloride collects in the flask on opening the tap.

(h) Fractional distillation can be used to separate benzene from a mixture of benzene [b.p. 80°C] & toluene [b.p. 110°C]

Process — Mixture is kept in a distillation flask 'X' with a fractionating column. The flask is then heated as shown and the mixture evaporates and later condenses.

Higher boiling point liquid [toluene] remains in the flask X, after condensation.

Lower boiling point liquid [benzene] collects in the receiver Y, after condensation in Leibigs condenser.

(i) Chromatography can be used to separate different dyes - in their liquid constituent ink.

Process — Place the ink spot containing different dyes on the filter paper.

The filter paper is hung with its lower end completely dipped in the solvent.

The solvent flows over the ink spot and the dyes separate out as shown below.