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

Question

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 :

(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is NOT the correct explanation of A.
(C) A is true but R is false
(D) A is false but R is true

Prashant Kotian · Accepted Answer

Correct answer: C) A IS TRUE BUT R IS FALSE. Phenolphthalein is a pH dependent indicator. It is a weak acid which is colourless in the acidic solution but gives pink colour in basic medium. The pink colour is due to its conjugate form. Phenolphthalein dissociate in basic medium. Therefore, the assertion is true but the reason is false.

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