Question

The highest grade of coal, whose surface is shining and has the highest calorific value is;
A. bituminous
B. peat
C. anthracite
D. lignite

Answer 1

Hint: Coal is a solid carbon rich fossil fuel. It generally occurs in stratified sedimentary deposits. It is utilised as a source of energy. The energy which is found in the fuel and is obtained by the calculation of the heat produced by the complete combustion of the specified quantity is called calorific value.

Complete step by step combustion
There are various types of coal and they have also been ranked on the basis of their calorific value, carbon content and impurities present. They are discussed below.
Peat :- Peat is a precursor to coal as when placed under high heat and pressure, it leads to the formation of coal. Actually peat is a soft organic substance containing decayed plants and deposited minerals.
Lignite:- Lignite is that type of coal which contains the least amount of carbon. This is also referred to as brown coal because of its appearance. Also, it contains a high amount of impurities. Due to the least concentration of carbon and the higher concentration of impurities it has least calorific value.
Bituminous :- Bituminous is ranked at second position. It has a relatively higher carbon concentration and thus has high energy density. It is soft and appears to have a shiny surface.
Anthracite:- Anthracite is a compact variety of coal in which the carbon content is the highest along with very few impurities. Anthracite is ranked at the top among all the types of coal because of several qualities. Since the anthracite has the submetallic lustre i.e. a shining surface and is hard in nature, it is also called “hard coal”. The energy density of the anthracite is highest among all the various varieties of coal and thus has the highest calorific value.

Hence, option (C) Anthracite, is the correct option.

Note:
Anthracite is the highest grade of coal as it has highest energy density i.e. the calorific value because of the presence of a fairly high amount of carbon and very few impurities. It has submetallic characters like hardness, brittleness and lustre.