An acidic gas does not turn dry blue litmus red but turns moist blue litmus red. What does this prove?
Answer and explanation
Correct answer: Ions form in the presence of water
Acidic behaviour is produced by ions in aqueous conditions, especially hydrogen or hydronium ions. The gas cannot ionise the dry litmus paper sufficiently, so no colour change is observed. When the paper is moist, the gas dissolves in water and forms ions, which interact with the indicator and turn it red. Thus the observation demonstrates the role of water in ion formation; option A is correct.
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What is the correct answer to this question?
Ions form in the presence of water
Why is this the correct answer?
Acidic behaviour is produced by ions in aqueous conditions, especially hydrogen or hydronium ions. The gas cannot ionise the dry litmus paper sufficiently, so no colour change is observed. When the paper is moist, the gas dissolves in water and forms ions, which interact with the indicator and turn it red. Thus the observation demonstrates the role of water in ion formation; 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.
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