Under which condition can carbon dioxide remove the milkiness of lime water?
Answer and explanation
Correct answer: When carbon dioxide is passed in excess
The governing concept is the reaction of carbon dioxide with lime water, which is aqueous calcium hydroxide. Initially, carbon dioxide forms insoluble calcium carbonate, Ca(OH)2 + CO2 → CaCO3 + H2O, producing milkiness. When carbon dioxide is passed in excess, the precipitate reacts further to form soluble calcium hydrogen carbonate, CaCO3 + CO2 + H2O → Ca(HCO3)2. The precipitate dissolves, so option A is correct; the other conditions do not cause this change.
Frequently asked questions
What is the correct answer to this question?
When carbon dioxide is passed in excess
Why is this the correct answer?
The governing concept is the reaction of carbon dioxide with lime water, which is aqueous calcium hydroxide. Initially, carbon dioxide forms insoluble calcium carbonate, Ca(OH)2 + CO2 → CaCO3 + H2O, producing milkiness. When carbon dioxide is passed in excess, the precipitate reacts further to form soluble calcium hydrogen carbonate, CaCO3 + CO2 + H2O → Ca(HCO3)2. The precipitate dissolves, so option A is correct; the other conditions do not cause this change.
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.
