Which one of the following compounds is used as a chemical in certain type of fire extinguishers?

Solution

Chemistry ma’am · 3 steps

Ask which of these four gives off CO₂ easily: that gas is what puts the fire out.

1. What an extinguisher needs. A fire needs oxygen. A heavy, non-burning gas like CO₂ settles over the flame and cuts off the air, so the chemical must release CO₂ quickly.

   Common name	Formula	Releases CO₂ easily?
   Baking soda	NaHCO₃	Yes: with acid, or on mild heating
   Soda ash	Na₂CO₃	No, stable even on strong heating
   Washing soda	Na₂CO₃.10H₂O	No, heating only drives off water
   Caustic soda	NaOH	No, it contains no carbon

2. How it works. In a soda-acid extinguisher, NaHCO₃ meets H₂SO₄ and gives CO₂. In dry-powder extinguishers, the heat of the fire breaks it down: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂.
3. So. The fire-extinguisher chemical is baking soda, NaHCO₃, which is option (a).

The idea to keep. Learn the sodium compounds by formula, not only by name: baking soda is NaHCO₃, soda ash is Na₂CO₃, washing soda is Na₂CO₃.10H₂O, caustic soda is NaOH.

Answer from the NTA final answer key. Solution by PrepWiser.