Ammonia gas turns moist red litmus blue but has no effect on dry red litmus. What does this prove?
Answer and explanation
Correct answer: Ammonia forms a basic solution in moisture
Ammonia itself is a covalent gas, but in the presence of water it dissolves and reacts reversibly to form ammonium and hydroxide ions: NH3 + H2O ⇌ NH4+ + OH−. The hydroxide ions turn moist red litmus blue. Dry litmus lacks the water needed for this ion formation, so it shows no change. Thus option A is correct; the observation does not mean ammonia is a strong acid or always neutral.
Frequently asked questions
What is the correct answer to this question?
Ammonia forms a basic solution in moisture
Why is this the correct answer?
Ammonia itself is a covalent gas, but in the presence of water it dissolves and reacts reversibly to form ammonium and hydroxide ions: NH3 + H2O ⇌ NH4+ + OH−. The hydroxide ions turn moist red litmus blue. Dry litmus lacks the water needed for this ion formation, so it shows no change. Thus option A is correct; the observation does not mean ammonia is a strong acid or always neutral.
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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