A dilute acid is added to a white solid, producing a gas that turns lime water milky. What could the white solid be?
Answer and explanation
Correct answer: Calcium carbonate
The governing qualitative test is that carbon dioxide turns limewater milky by forming insoluble calcium carbonate: CO₂ + Ca(OH)₂ → CaCO₃ + H₂O. Acids react with carbonates to release carbon dioxide, so white calcium carbonate can produce this observation. Option A is therefore correct. Sodium chloride and copper sulphate do not normally release CO₂ with dilute acid, while sodium hydroxide neutralises acid instead of giving this gas.
Frequently asked questions
What is the correct answer to this question?
Calcium carbonate
Why is this the correct answer?
The governing qualitative test is that carbon dioxide turns limewater milky by forming insoluble calcium carbonate: CO₂ + Ca(OH)₂ → CaCO₃ + H₂O. Acids react with carbonates to release carbon dioxide, so white calcium carbonate can produce this observation. Option A is therefore correct. Sodium chloride and copper sulphate do not normally release CO₂ with dilute acid, while sodium hydroxide neutralises acid instead of giving this gas.
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.
