Why does dry hydrogen chloride gas not change the colour of dry litmus paper?
Answer and explanation
Correct answer: Acidic ions are not formed in the absence of water
The governing concept is that acids show their characteristic behaviour in aqueous solution. Dry hydrogen chloride gas does not dissociate to produce hydrogen ions without water, so dry litmus has no acidic ions with which to react. Therefore option A is correct. Litmus can identify acids, and hydrogen chloride itself is not basic. When the litmus is moist, HCl dissolves and ionises, allowing the expected colour change to occur.
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?
The governing concept is that acids show their characteristic behaviour in aqueous solution. Dry hydrogen chloride gas does not dissociate to produce hydrogen ions without water, so dry litmus has no acidic ions with which to react. Therefore option A is correct. Litmus can identify acids, and hydrogen chloride itself is not basic. When the litmus is moist, HCl dissolves and ionises, allowing the expected colour change to occur.
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.
