Why does dry hydrogen chloride gas not change the colour of dry litmus?
Answer and explanation
Correct answer: Ions do not form without water
The governing concept is that hydrogen chloride shows acidic behaviour only after dissolving in water. In moist conditions, HCl ionises in water and produces hydronium ions, which change blue litmus to red. Dry HCl gas and dry litmus contain no water medium, so the necessary ions are not formed and no colour change occurs. Thus option A is correct; the gas is not basic, litmus is not a metal, and colourlessness is irrelevant.
Frequently asked questions
What is the correct answer to this question?
Ions do not form without water
Why is this the correct answer?
The governing concept is that hydrogen chloride shows acidic behaviour only after dissolving in water. In moist conditions, HCl ionises in water and produces hydronium ions, which change blue litmus to red. Dry HCl gas and dry litmus contain no water medium, so the necessary ions are not formed and no colour change occurs. Thus option A is correct; the gas is not basic, litmus is not a metal, and colourlessness is irrelevant.
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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