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Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Phenolphthalein is a pH dependent indicator, remains colourless in acidic solution and gives pink colour in basic medium. Reason R: Phenolphthalein is a weak acid. It doesn’t dissociate in basic medium. In the light of the above statements, choose the most appropriate answer from the options given below.

1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is NOT the correct explanation of A
3. A is true but R is false
4. A is false but R is true

Correct answer: A is false but R is true

Solution

Assertion A is incorrect because phenolphthalein actually turns pink in basic solutions, not acidic ones, while Reason R is correct as it accurately describes phenolphthalein as a weak acid that does not dissociate in basic conditions.

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