Question

The thick black aromatic liquid with an unpleasant odour is known as?
A.Naptha
B.Gasoline
C.Coal Tar
D.Diesel Oil

Answer 1

Hint: To answer this question, one needs to know about the industrial synthesis of coke from coal, in presence of coal gas. This process is also known as “coking” in which the coal is subjected to pyrolysis, in absence of air at temperatures as high as ${2000^0}C$ , initially started at around ${1000^0}C$.

Complete step by step answer:
During the pyrolysis of coal at temperatures higher than ${1000^0}C$ , the volatile compounds are released in the form of different gases and compounds such as crude benzol, coal tar, water, and coal gas. This coal tar is the thick black viscous aromatic liquid which consists of polycyclic aromatic hydrocarbons whose boiling points are above ${180^0}C$ and can be separated by condensation. The liquid is thick due to the presence of different compounds with high molecular weights. . In this process several volatile organic compounds are released in the form of coal-gas and coal-tar.

So, the correct option is C.

Note:
-There are different varieties of coal among which the bituminous coal is mainly used to the coke.
-The general chemical reaction for the coking of coal is:
\[4{\left( {{C_3}{H_4}} \right)_n} \to n{C_6}{H_6} + 5nC + 3n{H_2} + nC{H_4}\]
-The components of tar are separated and are stored in a tar storage tank. The lighter components of the tar are treated with lime $Ca{\left( {OH} \right)_2}$ and steam.
-The different components of the tar are used for different purposes and are sometimes the primary components for the manufacture of carbon black, adhesives, roofing materials, etc.