Which two factors can reduce the quality of sodium hydroxide when it is kept in open air?
Answer and explanation
Correct answer: Moisture and carbon dioxide
The governing concept is the hygroscopic and reactive nature of sodium hydroxide. Solid NaOH absorbs water vapour from air, so it becomes moist and its effective concentration or purity changes. It also reacts with atmospheric carbon dioxide to form sodium carbonate: 2NaOH + CO₂ → Na₂CO₃ + H₂O. Both processes reduce the quality of the stored chemical. Therefore option A is correct; oxygen, nitrogen, light, sound, glass, and rubber do not explain the stated loss under ordinary storage conditions.
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What is the correct answer to this question?
Moisture and carbon dioxide
Why is this the correct answer?
The governing concept is the hygroscopic and reactive nature of sodium hydroxide. Solid NaOH absorbs water vapour from air, so it becomes moist and its effective concentration or purity changes. It also reacts with atmospheric carbon dioxide to form sodium carbonate: 2NaOH + CO₂ → Na₂CO₃ + H₂O. Both processes reduce the quality of the stored chemical. Therefore option A is correct; oxygen, nitrogen, light, sound, glass, and rubber do not explain the stated loss under ordinary storage conditions.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
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