Carbon dioxide first makes lime water milky and then removes the milkiness in excess. Why does this happen?
Answer and explanation
Correct answer: First calcium carbonate and then soluble calcium hydrogen carbonate forms
The governing concept is the reaction of carbon dioxide with lime water, which is aqueous calcium hydroxide. At first, CO₂ reacts as Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. Insoluble calcium carbonate particles scatter light and make the solution milky. When excess CO₂ is passed, CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂. Calcium hydrogen carbonate is soluble, so the suspended solid disappears and the milkiness is removed. Therefore option A is correct; the other options describe unrelated products.
Frequently asked questions
What is the correct answer to this question?
First calcium carbonate and then soluble calcium hydrogen carbonate forms
Why is this the correct answer?
The governing concept is the reaction of carbon dioxide with lime water, which is aqueous calcium hydroxide. At first, CO₂ reacts as Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. Insoluble calcium carbonate particles scatter light and make the solution milky. When excess CO₂ is passed, CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂. Calcium hydrogen carbonate is soluble, so the suspended solid disappears and the milkiness is removed. Therefore option A is correct; the other options describe unrelated products.
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.
