Question

Which of the following is necessary for combustion?
A.Air
B.Water
C.Light
D.Heat

Answer 1

Hint: Combustion is a process in which a substance burns in the presence of oxygen, giving off heat and light in the process. Moreover, the substances that produce heat on combustion are known as combustion fuels.

Complete step by step answer:
Combustion basically refers to the spontaneity with which a substance reacts with oxygen. It is considered as one of the oldest technologies of mankind and one of the most important discoveries or inventions.
Now, we have two types of combustion:
1.Complete combustion- In this type of combustion, the reaction takes place in the presence of abundant oxygen and the substances combine with oxygen to their maximum extent.
2.Incomplete combustion- These are the reactions that occur in the absence of oxygen and because of which the substances are unable to burn completely.
Thus, oxygen is the most necessary constituent for any combustible reaction and if the supply of oxygen (air) is cut, then combustion will stop immediately.
Some important combustion reactions and their equation are:
Naphthalene undergoes combustion in the presence of oxygen to afford carbon dioxide gas and water. The equation is :
  $12{O_2} + {C_{10}}{H_8} \to 4{H_2}O + 10C{O_2}$
The combustion of methanol involves a chemical reaction between methanol and oxygen. The equation is as shown:
  $2C{H_3}OH + 3{O_2} \to 4{H_2}O + 2C{O_2}$

Hence, option A is correct.

Note:
Some common examples of combustion are burning of sulfur in air, explosion of hydrogen in air, burning of wax candles, burning of natural gas in a Bunsen burner, combustion of petrol in a car’s engine etc.