In an experiment with dry ammonia gas and moist red litmus paper, why can the litmus turn blue?
Answer and explanation
Correct answer: Ammonia forms basic ions in water
Ammonia gas itself needs moisture to show its basic behaviour. On the wet litmus, NH₃ dissolves in water and reacts: NH₃ + H₂O ⇌ NH₄⁺ + OH⁻. The hydroxide ions make the moist paper basic, so red litmus turns blue. Therefore option A is correct. Dry ammonia cannot ionise effectively without water, and the other options contradict the indicator test.
Frequently asked questions
What is the correct answer to this question?
Ammonia forms basic ions in water
Why is this the correct answer?
Ammonia gas itself needs moisture to show its basic behaviour. On the wet litmus, NH₃ dissolves in water and reacts: NH₃ + H₂O ⇌ NH₄⁺ + OH⁻. The hydroxide ions make the moist paper basic, so red litmus turns blue. Therefore option A is correct. Dry ammonia cannot ionise effectively without water, and the other options contradict the indicator test.
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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