When calcium carbonate is heated, the gas produced turns limewater milky. Which gas is it?
Answer and explanation
Correct answer: Carbon dioxide
Heating calcium carbonate causes thermal decomposition: CaCO₃ → CaO + CO₂. The released carbon dioxide reacts with calcium hydroxide in limewater to form insoluble calcium carbonate, producing a milky appearance: CO₂ + Ca(OH)₂ → CaCO₃ + H₂O. Thus option C is correct. Oxygen, hydrogen, and nitrogen do not give this characteristic limewater test under these conditions.
Frequently asked questions
What is the correct answer to this question?
Carbon dioxide
Why is this the correct answer?
Heating calcium carbonate causes thermal decomposition: CaCO₃ → CaO + CO₂. The released carbon dioxide reacts with calcium hydroxide in limewater to form insoluble calcium carbonate, producing a milky appearance: CO₂ + Ca(OH)₂ → CaCO₃ + H₂O. Thus option C is correct. Oxygen, hydrogen, and nitrogen do not give this characteristic limewater test under these conditions.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Chemical Reactions and Equations.
