Milkiness of lime water is due to which substance?
Answer and explanation
Correct answer: Calcium carbonate
The governing concept is precipitation during the carbon-dioxide test. Lime water contains dissolved calcium hydroxide. Carbon dioxide reacts with it according to Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. Calcium carbonate is a fine, insoluble white precipitate, and its suspended particles scatter light, producing the observed milkiness. Thus option A is correct. Sodium chloride and sodium hydroxide do not cause this characteristic precipitate, while hydrogen gas is not formed.
Frequently asked questions
What is the correct answer to this question?
Calcium carbonate
Why is this the correct answer?
The governing concept is precipitation during the carbon-dioxide test. Lime water contains dissolved calcium hydroxide. Carbon dioxide reacts with it according to Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. Calcium carbonate is a fine, insoluble white precipitate, and its suspended particles scatter light, producing the observed milkiness. Thus option A is correct. Sodium chloride and sodium hydroxide do not cause this characteristic precipitate, while hydrogen gas is not formed.
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.
