write an advantage of heating coal strongly in the absence of air rather than burning ot straight away
Answers
Answer:
The process of heating coal in the absence of air is called the destructive distillation of coal. Coal contains a number of elements such as carbon, hydrogen, oxygen, nitrogen and sulphur. When coal is heated in the absence of air, a number of products are obtained.
The main products obtained by the destructive distillation of coal are as follows:
(1) Coke (2) Coal tar (3) Coal gas
(1) Coke: contains 98 % carbon. It is porous, tough, black and the purest form of coal. Like charcoal, it Is a good fuel and burns without smoke. It is largely employed as a reducing agent in the extraction of metals from their ores. It is also used in making fuel gases like water gas and producer gas.
(2) Coal tar (liquid): Coal tar is a mixture of different carbon compounds. It thick, black liquid with unpleasant smell. The fractional distillation of coal tar gives many chemical substances which are used in the preparation of dyes, explosives, paints, synthetics fibers, drugs, and pesticides. Some of these chemical substances are benzene, toluene, phenol and aniline. Naphthalene balls used to repel moth and other insects are also obtained from coal tar.
(3) Coal Gas: Coal gas is mainly a mixture of hydrogen, methane and carbon monoxide. The gases present in coal gas are combustible and hence, it is an excellent fuel. It has high calorific value. It was used for lighting houses, factories and streets in Mumbai until 1950. It was also used for cooling earlier.