Answer.
(a); Coal has become a major source of organic compounds. These compounds are obtained by destructive distillation. The strong heating of coal in the absence of air is called destructive distillation. Coal contains elements like carbon, hydrogen, oxygen, nitrogen, and sulphur. So destructive distillation of coal provides a large number of organic compounds along with a few inorganic compounds.
(b) Different types of products of coal;
(i) Coal Gas is mixture of hydrogen, methane and carbon monoxide. It produces heat when burnt in air. Therefore, it is mainly used as a fuel in industry,It is also used to provide an inert or reducing atmosphere in various metallurgical processes.
(ii) Ammonical Liquor is a solution of ammonia gas in water. It is used to prepare nitrogenous fertilizers. For example, when it is treated with sulphuric acid, it produces ammonium sulphate, fertilizer.
(iii) Coal-Tar is a thick black liquid. It is admixture of more than 200 different organic compounds, mostly aromatic. These compounds are separated by fractional distillation. Some of the important aromatic compounds are benzene, phenol, toluene, aniline, etc. These chemicals are used to synthesize drugs, dyes, explosives, paints, varnishes, plastics, synthetic fiber and pesticides. Besides these valuable chemicals, the black residue of the coal tar is called pitch. It is used for surfacing of roads and roofs.
(iv) Coke is 98% carbon. It is left behind residue of coal. When coal is subjected to destructive distillation, it loses all its volatile components and leaves behind a solid residue called coke. It is mainly used as a reducing agent in the extraction of metals | especially iron. It is also used as fuel.