HETEROGENEOUS MIXTURE CONSISTING OF TWO CRYSTALLINE SOLID CONSTITUENTS
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The crystals differ in their shape and size so they can be easily separated by hand picking, or using sieve.
For example:
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A mixture of potash alum and nitre (potassium nitrate):
The crystals of potash alum are octahedral in shape while those of nitre are needle like in shape.
Separation can be done by simple hand picking or picking with a forcep.
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Wheat grains can be separated from husk by using sieve of specific pore size.
Example-1:
You are given an impure sample of sugar containing impurity of some chalk. How will you purify it?
Solution:
The mixture is a heterogeneous mixture and can be separated by physical methods of separation.
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In order to purify the sample or to recover sugar from it, dissolve about 5g of the sample in minimum volume of water in a beaker. Stir occasionally with a glass rod.
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Filter the solution formed through funnel. The chalk impurity will be left on the filter paper. The filtrate will be a sugar solution in water.
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Transfer the solution in a china dish. Concentrate by heating so that the volume of the solution becomes nearly half. The solution will be saturated.
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Place the china dish over a beaker full of water and keep it undisturbed for sometime. Pure crystals of sugar will appear in the dish. They can be separated by using filtration technique.
Example-2:
Separate the constituents from a mixture containing ammonium chloride, sand and iron-filings.
Solution:
The mixture is a heterogeneous mixture and can be separated by physical methods of separation.
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Place the mixture on a paper or petri-dish. Move a magnet over it. Iron filings will get attached to the magnet. Scrap off iron filings from the magnet and collect them separately. Transfer the remaining mixture to a china dish and subject it to the sublimation process. Ammonium chloride will form the sublimate while sand will be left as residue in the dish.