Why can excess carbon dioxide remove the milkiness of lime water?
Answer and explanation
Correct answer: Soluble calcium hydrogen carbonate forms
Initially, carbon dioxide reacts with calcium hydroxide in limewater to form insoluble calcium carbonate, causing milkiness. When excess CO₂ is passed, the precipitate reacts further: CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂. Calcium hydrogen carbonate is soluble in water, so the solid precipitate disappears and the milkiness is removed. Hence option A is correct; the other choices do not explain this reaction.
Frequently asked questions
What is the correct answer to this question?
Soluble calcium hydrogen carbonate forms
Why is this the correct answer?
Initially, carbon dioxide reacts with calcium hydroxide in limewater to form insoluble calcium carbonate, causing milkiness. When excess CO₂ is passed, the precipitate reacts further: CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂. Calcium hydrogen carbonate is soluble in water, so the solid precipitate disappears and the milkiness is removed. Hence option A is correct; the other choices do not explain this reaction.
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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