In an experiment, dry litmus is unaffected, but the same gas changes moist litmus colour. What is the best conclusion?
Answer and explanation
Correct answer: The gas needs moisture to show acidic or basic properties
The governing concept is that acid or base behaviour of many gases appears only in the presence of water. Moisture allows the gas to dissolve and form ions; those ions then interact with the litmus indicator and change its colour. Dry litmus lacks the water needed for this ion formation, so it remains unchanged. Therefore option A is correct. The other options incorrectly call the indicators defective or deny that the gas is a substance.
Frequently asked questions
What is the correct answer to this question?
The gas needs moisture to show acidic or basic properties
Why is this the correct answer?
The governing concept is that acid or base behaviour of many gases appears only in the presence of water. Moisture allows the gas to dissolve and form ions; those ions then interact with the litmus indicator and change its colour. Dry litmus lacks the water needed for this ion formation, so it remains unchanged. Therefore option A is correct. The other options incorrectly call the indicators defective or deny that the gas is a substance.
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.
