An unknown sample reacts with acid to give a gas that turns lime water milky. Which class could the sample belong to?
Answer and explanation
Correct answer: Carbonate or hydrogen carbonate
Limewater turns milky when carbon dioxide passes through it because insoluble calcium carbonate forms: CO₂ + Ca(OH)₂ → CaCO₃ + H₂O. Acids react with carbonates and hydrogen carbonates to release carbon dioxide, for example, CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂. Therefore option A is correct. The other classes are too restrictive or do not generally produce this gas with acid.
Frequently asked questions
What is the correct answer to this question?
Carbonate or hydrogen carbonate
Why is this the correct answer?
Limewater turns milky when carbon dioxide passes through it because insoluble calcium carbonate forms: CO₂ + Ca(OH)₂ → CaCO₃ + H₂O. Acids react with carbonates and hydrogen carbonates to release carbon dioxide, for example, CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂. Therefore option A is correct. The other classes are too restrictive or do not generally produce this gas with acid.
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.
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