Question

Explain with the help of a labelled diagram, how a soda-acid type fire extinguisher works?

Answer 1

Hint: The main principle of a fire extinguisher is to cut off the supply of air or oxygen which causes the fire. In a soda-type fire extinguisher, the acid used is sulfuric acid and the soda used is baking soda.

Complete step by step solution:
There are three conditions on which the principle of working of any fire extinguisher works:
(a)- Lowering the combustible substance or material below its ignition temperature.
(b)- By cutting off the supply of air or oxygen.
(c)- Lowering the combustible substance or material at the same time cutting the supply of air or oxygen.
So the soda-acid type fire extinguisher mainly works on the second principle i.e., by cutting off the supply of air or oxygen. Except for the fire caused by electrical or flammable liquid, soda-acid type extinguishers can be used for all types of fire.
The acid used in this is sulfuric acid ($H_{2}S{O}_4$) and the soda used is baking soda ($NaHC{O}_3$). So when an acid reacts with baking soda it liberates carbon dioxide and thereby increases the percentage of carbon dioxide in the air. Carbon dioxide becomes a barrier to the supply of oxygen.
Soda-acid type fire extinguishers have a bottle that contains sulfuric acid which is supported by a metallic container filled with baking soda. So when this cylinder is inverted the knob opens and the acid comes in contact with baking soda producing a large amount of carbon dioxide. The reaction is:
$2NaHC{O}_3+H_{2}S{O}_4\to N{a}_{2}S{O}_4+2H_{2}O+2C{O}_2$
So this carbon dioxide cuts off the supply of air or oxygen and hence the fire is extinguished. The diagram of a soda-acid type fire extinguisher is:

Note: In multistory buildings, cinema halls, etc this type of fire extinguisher is mostly used. Water, foam, carbon dioxide, dry powder, and wet chemicals are the type of different fire extinguishers.