Science (086) — AI-generated practice question

NaHCO₃ in Fire Extinguishers:
When NaHCO₃ is heated (or reacts with acid in the extinguisher), it decomposes to release CO₂ gas. CO₂ being heavier than air cuts off the oxygen supply to the fire, extinguishing it.

$$2\text{NaHCO}_3 \xrightarrow{\Delta} \text{Na}_2\text{CO}_3 + \text{H}_2\text{O} + \text{CO}_2\uparrow$$

In soda-acid extinguishers, NaHCO₃ reacts with H₂SO₄:

$$2\text{NaHCO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O} + 2\text{CO}_2\uparrow$$

NaHCO₃ as Antacid:
When excess acid (HCl) is produced in the stomach, NaHCO₃ neutralises it, relieving indigestion. It is a mild, non-corrosive base, safe for consumption.

$$\text{NaHCO}_3 + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O} + \text{CO}_2\uparrow$$

Thus, the same compound acts as a CO₂ source in fire-fighting and as a mild base (antacid) in medicine.

Source: Acids, Bases and Salts, Chapter 2; uses of baking soda

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• 5 marks → ~5 key points: name the two uses, give the mechanism for each, write correct balanced equations (2 equations minimum), and conclude.
• Examiners look for both equations and the reason (CO₂ smothers fire; base neutralises stomach acid).
• Note: in soda-acid extinguishers the acid triggers the reaction; thermal decomposition is the other route — mentioning either is fine, but both scores higher.
• The word "mild/non-corrosive base" is important for the antacid explanation — it distinguishes NaHCO₃ from stronger, harmful bases.
• "What you have learnt" (Ch. 2) confirms: acid + hydrogencarbonate → salt + CO₂ + water. Use that reaction pattern for the antacid equation.