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.
(a) What could P, Q, R and S be?
(b) How would you separate a mixture containing P, Q, R and S?
(a) P is sand; Q is common salt; R is iron filings; S is ammonium chloride
(b) First separate R (iron filings) by using a magnet to attract them. Then separate S (ammonium chloride) by sublimation. Shake P (sand) and Q (common salt) with water and filter. Sand is obtained as residue. Evaporate filtrate to dryness to obtain common salt.