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

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

Solution

Phenolphthalein, (C20H14O4), an organic compound of the phthalein family that is widely employed as an acid-base indicator. As an indicator of a solution’s pH, phenolphthalein is colourless below pH 8.5 and attains a pink to deep red hue above pH 9.0.

Phenolphthalein dissociate in basic medium

HPhaqcolourless⇌H++Ph-Pink

Asked in: JEE Main 2022 (26 Jul Shift 2)

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