Why can the purity of sodium hydroxide decrease when it is left exposed to air?
Answer and explanation
Correct answer: It can react with carbon dioxide
Sodium hydroxide is a strong, hygroscopic base that can absorb moisture and react with carbon dioxide from air. The acidic oxide CO₂ reacts with NaOH to form sodium carbonate, or sodium hydrogen carbonate under some conditions; for example, 2NaOH + CO₂ → Na₂CO₃ + H₂O. This converts part of the original substance into another compound and lowers its purity. Therefore option A is correct.
Frequently asked questions
What is the correct answer to this question?
It can react with carbon dioxide
Why is this the correct answer?
Sodium hydroxide is a strong, hygroscopic base that can absorb moisture and react with carbon dioxide from air. The acidic oxide CO₂ reacts with NaOH to form sodium carbonate, or sodium hydrogen carbonate under some conditions; for example, 2NaOH + CO₂ → Na₂CO₃ + H₂O. This converts part of the original substance into another compound and lowers its purity. Therefore option A is correct.
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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