Question

The residue left in the destructive distillation of coal is:
A) Charcoal
B) Coke
C) Coal tar
D) Coal gas

Answer 1

The destructive distillation is a process in which the complex organic molecules break down into smaller and simpler molecules. During the destructive distillation of coal, it generates various small molecules. The coal forms pure carbon as the residue.

Complete answer:
Coal is one of the most commonly used natural hydrocarbons. It is obtained by mining. The coal is a black or brownish-black and rock-like substance that is made up of carbon, hydrogen, oxygen, nitrogen, or sulphur.
Coal formation takes millions of years. It is formed by the decomposition of the organic plant which undergoes the heat and pressure in the absence of oxygen for about 300 millions of years.
When coal is heated in the air, coal burns down and produces mainly carbon dioxide along with heat energy. It is used to generate electricity in power stations. Coal undergoes destructive distillation.
The chemical process which takes place on the unprocessed materials so that the material undergoes the decomposition of heating and produces ‘cracks’ in the larger molecules is called the destructive distillation.
The term ‘destructive distillation’ stands for the processing of organic material in the limited supply of oxygen and reagent, solvents, or catalyst.
The destructive distillation as the name suggests destructs the larger molecules by forming a ‘crack’ in them.
One of the common examples of destructive distillation is the cracking of coal. When coal is subjected to destructive distillation produces a wide range of commercially important products. The products can be coke, coal oil, ammonium hydroxide, coal tar, coal gas, etc.
Coal is a complex substance when heated in a limited supply of air breaks down into simpler substances. The coal is heated ${{1000}^{0}}C$ in the absence of air.
The reaction is as shown below:
$\begin{matrix} \text{Coal} & \xrightarrow{\text{Destrucive Distillation}} & \text{Coke} & \text{+ Coal tar} & \text{+ Coal gas} & \text{+ Ammonical solution} \\\ \end{matrix}$
The coal tar is a thick black liquid that has an unpleasant smell. It is a complex organic compound and can be separated by the various simpler compounds for further use.
Coal gas is a mixture of hydrogen, methane, carbon monoxide, and other gases. It was used for domestic fuel.
Coke is a porous and black substance that is left as residue when coal is subjected to destructive distillation. It is a pure form of carbon that contains the $90{\scriptstyle{}^{0}/{}_{0}}$ carbon in it.
Thus, when coal undergoes the destructive distillation the coke is obtained as the residue.

Hence, (B) is the correct option.

Note:
The destructive distillation may seem like a fractional distillation. Though there is some major difference. In destructive distillation, components are separated by the decomposition of the solid. In fractional distillation, the components are separated by a difference in boiling point. It is used for the separation of hydrocarbons from crude oil.