Dry hydrogen chloride gas has no effect on dry litmus but turns blue litmus red after dissolving in water. What is the reason?
Answer and explanation
Correct answer: Hydrogen ions form in water
Hydrogen chloride shows its acidic behaviour only when water allows it to ionise. In water, HCl produces hydronium ions, H₃O⁺, which cause blue litmus to turn red. Dry HCl gas and dry litmus do not provide the aqueous medium needed for this ion formation, so no colour change occurs. Therefore option A explains both observations; the other choices are incorrect.
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What is the correct answer to this question?
Hydrogen ions form in water
Why is this the correct answer?
Hydrogen chloride shows its acidic behaviour only when water allows it to ionise. In water, HCl produces hydronium ions, H₃O⁺, which cause blue litmus to turn red. Dry HCl gas and dry litmus do not provide the aqueous medium needed for this ion formation, so no colour change occurs. Therefore option A explains both observations; the other choices are incorrect.
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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