Question

Fire extinguishers contain:
A. Conc. \[{H_2}S{O_4}\] solution
B. \[{H_2}S{O_4}\] and \[NaHC{O_3}\]
C. \[NaHC{O_3}\] solution
D. \[CaC{O_3}\] solution

Answer 1

Hint: The main principle behind the fire extinguisher is that the cooling of the combustible material and cutting off the air is done simultaneously. The reaction involves the formation of carbon dioxide which is heavier than air.

Complete step by step answer:
The fire extinguishers are the soda acid fire extinguisher which contains sodium bicarbonate and sulphuric acid. The fire extinguishers are used as household fire extinguishers containing strong iron vessels with side discharge nozzles. The vessel is filled with sodium bicarbonate solution.
The principle applied for the working of fire extinguishers is based in three conditions. The conditions are written below.
(1) The combustible material should be cooled below the ignition temperature.
(2) The air supply is cut off
(3) The cooling of combustible material and cutting off the supply of air should be done simultaneously.
The solution of sodium bicarbonate is present in the vessel of the fire extinguishers and sulphuric acid is present in another bottle. When the knob of the fire extinguisher is opened, the sulphuric acid reacts with sodium bicarbonate producing a large amount of carbon dioxide. As carbon dioxide is non-combustible and heavier than air, it cuts off the air supply of the oxygen and extinguishes the flame.
The reaction is shown below.
\[2NaHC{O_3} + {H_2}S{O_4} \to N{a_2}S{O_4} + 2{H_2}O + 2C{O_2}\]
In this reaction, two mole of sodium bicarbonate reacts with one mole of sulphuric acid to form one mole of sodium sulphate, two mole of water and two mole of carbon dioxide.
Thus, the fire extinguisher contains \[{H_2}S{O_4}\]and \[NaHC{O_3}\].

So, the correct answer is Option B.


Note: The fires can also be controlled by halogenated hydrocarbons such as halons, dry chemicals like sodium bicarbonate or ammonium dihydrogen phosphate.