CBSE Class 8 Answered

(a) Soda-acid fire extinguisher is not successful in controlling fire due to oils because it uses water to cool the combustible substance. But water is heavier than oil and settles down below the oil particles and oil keeps on burning on the top. Hence, fire cannot be controlled.

(b) Soda-fire extinguisher is based on cooling the temperature of the burning object. This type of fire extinguisher contains sulphuric acid and sodium bicarbonate. When the extinguisher becomes functional, the sulphuric acid reacts with sodium bicarbonate to produce carbon dioxide. Carbon dioxide when released cuts off the supply of oxygen and water is released to bring down the ignition temperature of the burning object. In this way, fire is controlled.