Question

A teacher gave an impure sample of alum containing fine sand as impurity to a student. He asked him to recover pure alum from this sample. The correct procedure to be followed would be to
(1) dissolve the impure sample of alum in water, filter and evaporate the filtrate (2) dissolve the impure sample of alum in alcohol and filter
(3) move a magnet over the impure sample of alum
(4) dissolve the impure sample of alum in carbon disulphide, filter and evaporate the filtrate to dryness.

Answer 1

Explanation:

4 th option

As cs2 dissolves many things like sulphur etc.

In case we use magnet then we will not get sufficient results.

Alum also gets evaporated so 1st option is also inappropriate

Dissolvation in alcohol and filter is correct but we must evaporate it later

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