Why does dry hydrogen chloride gas not turn dry blue litmus paper red?
Answer and explanation
Correct answer: Hydrogen ions do not form without water
Hydrogen chloride shows acidic behaviour when it dissolves in water and ionises, producing hydronium ions, H₃O⁺, which are responsible for the acidic reaction. Dry HCl gas in contact with dry blue litmus has no water available for this ionisation, so the ions are not produced and the litmus remains unchanged. Hence option A is correct; colourlessness or basicity is unrelated to the result.
Frequently asked questions
What is the correct answer to this question?
Hydrogen ions do not form without water
Why is this the correct answer?
Hydrogen chloride shows acidic behaviour when it dissolves in water and ionises, producing hydronium ions, H₃O⁺, which are responsible for the acidic reaction. Dry HCl gas in contact with dry blue litmus has no water available for this ionisation, so the ions are not produced and the litmus remains unchanged. Hence option A is correct; colourlessness or basicity is unrelated to the result.
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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