Which one of the following is used in soda-acid fire extinguishers ?

Soda-acid fire extinguishers utilize a chemical reaction between an acid and a metal hydrogen carbonate to produce carbon dioxide gas, which smothers the fire by displacing oxygen. Specifically, sodium hydrogen carbonate (also known as baking soda or sodium bicarbonate) is the primary 'soda' component used in these extinguishers [1]. When the extinguisher is activated, this compound reacts with an acid, typically sulphuric acid, to release a large volume of carbon dioxide gas, water, and a salt. This specific application of sodium hydrogen carbonate is a standard industrial and household use due to its alkaline nature and ability to release CO2 upon reaction or heating [1]. Other options like sodium chloride (table salt) or calcium hydroxide (slaked lime) do not serve this functional role in soda-acid systems.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Uses of Baking soda > p. 31