Chemistry NCERT Exemplar Solutions Class 12th Chapter Seven Chemistry NCERT Exemplar Solutions Class 12th Chapter Thirteen Equilibrium Class 12th Chemistry

Given below are two statements : one is labeled as Assertion A and the other is labeled as Reason R.

Assertion A: Phenolphthalein is 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.**

Option 1 - <p>Both A and R  are true and R is the correct explanation of A.</p>

Option 2 - <p>Both A and R are true but R is NOT the correct explanation of A.</p>

Option 3 - <p>A is true but R is false</p>

Option 4 - <p>A is false but R is true.</p>

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Answered by

Alok Kumar Singh | Contributor-Level 10

6 months ago

Correct Option - 3

Detailed Solution:

Phenolphtalein is a pH dependant indicator. It is a weak acid which is colourless in acidic medium but gives pink colour in basic medium. The pink colour is due to its conjugate form. Phenolphthalein dissociates in basic medium. Therefore, assertion is true but reason is false.

$\underset{(C o l o u r l e s s)}{H P h (a q .)} ? H^{+} + \underset{(P i n k)}{P h^{-}}$

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Chemistry NCERT Exemplar Solutions Class 12th Chapter Seven 2025

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