What is the chemical composition of a soda-acid type fire

What is the chemical composition of a soda-acid type fire extinguisher?

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Solution of sodium hydrogen carbonate and sulfuric acid

Solution of sodium carbonate and sulfuric acid

Solution of carbon dioxide and sulfuric acid

Solution of sodium chloride and sulfuric acid

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This question was previously asked in

UPSC CDS-1 – 2023

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A soda-acid fire extinguisher contains a solution of sodium hydrogen carbonate (NaHCO₃), also known as sodium bicarbonate or baking soda, and a separate container of sulfuric acid (H₂SO₄). When the extinguisher is activated, the acid mixes with the sodium bicarbonate solution. A chemical reaction occurs:
$2NaHCO_3 (aq) + H_2SO_4 (aq) \rightarrow Na_2SO_4 (aq) + 2H_2O (l) + 2CO_2 (g)$
This reaction produces a large volume of carbon dioxide gas (CO₂), which is expelled under pressure. The CO₂ gas is denser than air and blankets the fire, displacing oxygen and suppressing the combustion.

– Soda-acid fire extinguishers utilize the reaction between sodium hydrogen carbonate and sulfuric acid.
– The extinguishing agent is primarily carbon dioxide gas produced by the reaction.

Soda-acid extinguishers are effective on Class A fires (ordinary combustibles like wood, paper, textiles). They are not suitable for Class B (flammable liquids) or Class C (electrical) fires, and can be dangerous to use on electrical fires due to the water content. Modern fire extinguishers use different agents like foam, dry chemical powder, or CO₂ itself.

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