Question

Assertion: Phenolphthalein is an acid-base indicator.

Reason: The aqueous solution of a base NaOH is pinkish and it becomes colorless when dilute HCl is added dropwise to the solution.

• A. Both assertion and reason are correct and the reason is the correct explanation of the assertion.
• B. Both assertion and reason are correct but the reason is not the correct explanation of the assertion.
• C. The assertion is correct but the reason is incorrect.
• D. The assertion is incorrect but the reason is correct.

Answer 1

The correct option is A

Both assertion and reason are correct and the reason is the correct explanation of the assertion.

Explanation for the assertion statement:

This statement is true because phenolphthalein is color sensitive and changes its color based on the medium of the given solution.

Explanation for the reason statement:

This statement is true because

1. Phenolphthalein turns pink in basic solutions. and turns colorless in acidic solutions.
2. Thus when the solution of dilute Hydrochloric acid(HCl) is added dropwise the base gets neutralized and the pink color turns colorless.

Thus, both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

Therefore, option A is correct.