When carbon dioxide is passed into limewater, which substance causes the milkiness?
Answer and explanation
Correct answer: Calcium carbonate
Limewater is an aqueous solution of calcium hydroxide. When carbon dioxide is passed through it, the reaction is Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. Calcium carbonate is insoluble in water and appears as a white suspension, producing the milky appearance. If excess carbon dioxide is passed, soluble calcium hydrogen carbonate may form and the milkiness can disappear. Thus option A is correct.
Frequently asked questions
What is the correct answer to this question?
Calcium carbonate
Why is this the correct answer?
Limewater is an aqueous solution of calcium hydroxide. When carbon dioxide is passed through it, the reaction is Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. Calcium carbonate is insoluble in water and appears as a white suspension, producing the milky appearance. If excess carbon dioxide is passed, soluble calcium hydrogen carbonate may form and the milkiness can disappear. Thus 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.
