Question

Which one of the following is used as clean fuel?
A. petrol
B. mineral oil
C. methane
D. LPG

Answer 1

Hint: Fuels have hydrocarbons in it. When fuels undergo combustion reaction in the presence of oxygen, it produces carbon dioxide and water molecules. Some fuels may not undergo complete combustion. It may undergo incomplete combustion.

Complete step by step solution:
Incomplete combustion of fuels may sometimes produce carbon or carbon monoxide or sometimes smoke. Incomplete combustion occurs in the absence of sufficient oxygen. Now let’s focus on the options.
A. Petrol is synthesized from coal, natural gas or biomass. Fuels like petrol and diesel undergo incomplete combustion reactions to form carbon monoxide, carbon and water molecules. Some of these products are very harmful substances. Thus it cannot be considered as a clean fuel.
B. Mineral oils are generally mixtures of higher alkanes or sometimes cycloalkanes. It is a liquid. When crude oil is refined, mineral oil is formed as a by-product. It is not a clean fuel.
C. Major content of natural gas is methane. It undergoes complete combustion to form carbon dioxide and water molecules. Since the products formed are not harmful, it is considered as the clean fuel.
D. LPG is liquefied petroleum gas. This also contains different numbers of hydrocarbons. When these hydrocarbons undergo combustion reaction, it forms harmful substances. Thus it is not considered as clean fuel.
Hence, among the options, methane is used as clean fuel.

So, the correct option is C.

Note: Methane has wide varieties of uses. It is used for cooking purposes, drying cereals and fruits. During the manufacture of bricks, cement, plastics and fertilizers, methane is heated. These uses are made since the methane compound is a major content in natural gas.