Question

Assertion (A): Mercury is preferred in clinical thermometer over alcohol.
Reason (R): Alcohol has O–H polar bond.

• A. both A and R are correct and R is the correct explanation of A
• B. both A and R are correct but R is not the correct explanation of A
• C. A is correct but R is incorrect
• D. A is incorrect but R is correct

Hint:

In assertion–reason questions, always check whether the reason directly explains the assertion, not just whether both statements are true.

Answer 1

The Correct Option is B

Step 1: Analyze the Assertion (A).
Mercury is preferred in clinical thermometers because it expands uniformly, does not wet the glass, and can measure high temperatures accurately. Hence, the assertion is correct.
Step 2: Analyze the Reason (R).
Alcohol does have an O–H polar bond, which is a true statement from a chemical point of view. Therefore, the reason is also correct.
Step 3: Check the relationship between A and R.
Although alcohol has an O–H polar bond, this is not the reason why mercury is preferred over alcohol in clinical thermometers. Mercury is preferred due to its uniform expansion, visibility, and non-wetting nature, not because of the polarity of alcohol.
Step 4: Conclusion.
Both the assertion and the reason are correct individually, but the reason does not correctly explain the assertion.