Why can sodium hydroxide pellets become wet and then less pure in open air?
Answer and explanation
Correct answer: They can be affected by both moisture and carbon dioxide
Sodium hydroxide is deliquescent, so its pellets absorb water vapour from humid air and may become wet or dissolve. It also reacts with carbon dioxide in the atmosphere: 2NaOH + CO₂ → Na₂CO₃ + H₂O. The formation of sodium carbonate changes the composition of the material and lowers its purity for uses requiring NaOH. Therefore option A correctly includes both moisture absorption and chemical reaction with CO₂; the other statements have no chemical basis.
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What is the correct answer to this question?
They can be affected by both moisture and carbon dioxide
Why is this the correct answer?
Sodium hydroxide is deliquescent, so its pellets absorb water vapour from humid air and may become wet or dissolve. It also reacts with carbon dioxide in the atmosphere: 2NaOH + CO₂ → Na₂CO₃ + H₂O. The formation of sodium carbonate changes the composition of the material and lowers its purity for uses requiring NaOH. Therefore option A correctly includes both moisture absorption and chemical reaction with CO₂; the other statements have no chemical basis.
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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