Carbon dioxide first makes lime water milky and then removes the milkiness in excess. What is the second soluble substance?
Answer and explanation
Correct answer: Calcium hydrogen carbonate
Initially, carbon dioxide reacts with calcium hydroxide in limewater to form insoluble calcium carbonate, which causes milkiness: Ca(OH)2 + CO2 → CaCO3 + H2O. When excess CO2 is passed, the calcium carbonate reacts further and forms soluble calcium hydrogen carbonate: CaCO3 + CO2 + H2O → Ca(HCO3)2. Thus option A is correct; calcium carbonate is the first, insoluble product.
Frequently asked questions
What is the correct answer to this question?
Calcium hydrogen carbonate
Why is this the correct answer?
Initially, carbon dioxide reacts with calcium hydroxide in limewater to form insoluble calcium carbonate, which causes milkiness: Ca(OH)2 + CO2 → CaCO3 + H2O. When excess CO2 is passed, the calcium carbonate reacts further and forms soluble calcium hydrogen carbonate: CaCO3 + CO2 + H2O → Ca(HCO3)2. Thus option A is correct; calcium carbonate is the first, insoluble product.
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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