What is the main reason for the different effect of dry hydrogen chloride and moist hydrogen chloride on litmus?
Answer and explanation
Correct answer: Moisture helps ion formation
The governing concept is that acids show their characteristic properties through ions in aqueous solution. Dry hydrogen chloride gas does not produce hydrogen ions without water, so dry litmus shows no acidic colour change. In moisture, HCl dissolves and ionises as HCl + H₂O → H₃O⁺ + Cl⁻. The hydronium ions turn blue litmus red, making option A correct; the other statements contradict acid behaviour.
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What is the correct answer to this question?
Moisture helps ion formation
Why is this the correct answer?
The governing concept is that acids show their characteristic properties through ions in aqueous solution. Dry hydrogen chloride gas does not produce hydrogen ions without water, so dry litmus shows no acidic colour change. In moisture, HCl dissolves and ionises as HCl + H₂O → H₃O⁺ + Cl⁻. The hydronium ions turn blue litmus red, making option A correct; the other statements contradict acid behaviour.
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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