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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

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

Assertion A: Phenolphthalein is a \mathrm{ 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

 Both A and R are true and R is the correct explanation of A.


Option: 2

 Both A and R are true but R is NOT the correct explanation of A.


Option: 3

A is true but R is false.


Option: 4

A is false but R is true.


Answers (1)

best_answer

Phenolphthalein is a pH dependent indicator, remains colourless in acidic solution and gives pink colour in basic medium.

[Colourless in acid \rightarrow Pink in alkali]

Phenolphthalin is a weak acid, therefore it does not dissociate in the acidic medium and remain in the unionised form. Which is colourless.

So, A is true but R is false.

Hence, Option (3) is correct.

Posted by

Deependra Verma

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