Question

A solid mixture contains four constituents P, Q, R and S. P consists of tiny grains and it is mixed with
cement for plastering the walls. Q is a white solid which is recovered on a large scale from sea water by the
process of evaporation. R is in the form of tiny particles of a material whose corrosion is called rusting. And
S is a white solid which is used in making ordinary dry cells.

1. What could P, Q, R and S be ?
2. How would you separate a mixture containing P, Q, R and S ?

Answer 1

• P consists of tiny grains and it is mixed with cement for plastering the walls. So, P is sand. Q is a white solid, which is recovered on a large scale from sea water by the process of evaporation. It is common salt. R is in the form of tiny particles of materials, whose corrosion is called rusting. It is, iron filings. S is ammonium chloride.
• At first, let us take the mixture of P, Q, R, and S.

1. We first separate R (iron filings) by using a magnet to attract them. Then separate S (ammonium chloride) by sublimation.
2. Now, we shake P (sand) and Q (common salt) with water. The mixture is then filtered.
3. Sand is obtained as residue.
4. Now, we will evaporate the filtrate to dryness to obtain Q (common salt).