Ammonia turns moist red litmus blue but not dry red litmus. What does this show?
Answer and explanation
Correct answer: Basic ions form in moisture
Ammonia itself is a covalent gas, but in the presence of water it dissolves and reacts to produce hydroxide ions: NH₃ + H₂O ⇌ NH₄⁺ + OH⁻. The hydroxide ions make the solution basic and turn red litmus blue. Dry litmus lacks water, so this ion formation and colour change cannot occur. Hence option A is correct; the remaining choices misidentify the substance or indicator.
Frequently asked questions
What is the correct answer to this question?
Basic ions form in moisture
Why is this the correct answer?
Ammonia itself is a covalent gas, but in the presence of water it dissolves and reacts to produce hydroxide ions: NH₃ + H₂O ⇌ NH₄⁺ + OH⁻. The hydroxide ions make the solution basic and turn red litmus blue. Dry litmus lacks water, so this ion formation and colour change cannot occur. Hence option A is correct; the remaining choices misidentify the substance or indicator.
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.
