Dry hydrogen chloride gas has no effect on dry blue indicator paper. What is the most correct reason?
Answer and explanation
Correct answer: Acidic ions are not formed in the absence of water
Hydrogen chloride shows acidic behaviour only after dissolving in water, where it ionises and produces hydronium ions, H₃O⁺. Dry HCl gas cannot ionise on completely dry blue indicator paper, so the acid-sensitive colour change does not occur. It does not become a base, blue paper is not limited to bases, and gases still contain particles. Therefore option A is correct.
Frequently asked questions
What is the correct answer to this question?
Acidic ions are not formed in the absence of water
Why is this the correct answer?
Hydrogen chloride shows acidic behaviour only after dissolving in water, where it ionises and produces hydronium ions, H₃O⁺. Dry HCl gas cannot ionise on completely dry blue indicator paper, so the acid-sensitive colour change does not occur. It does not become a base, blue paper is not limited to bases, and gases still contain particles. Therefore option A is correct.
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.
