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JEE Main 202226 JulyEvening Shift
Exam
JEE Main
Year
2022
Date
26 July
Shift
Evening Shift
Subject
Chemistry
Chapter
Redox Reactions

JEE Main 2022 · 26 July · Evening Shift · Chemistry · Redox Reactions

Given below are two statements: one is labelled as Assertion A and...

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

Assertion AA :Phenolphthalein is a pHpH dependent indicator, remains colourless in acidic solution and gives pink colour in basic medium

Reason RR : 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

Options

  1. ABoth AA and RR are true and RR is the correct explanation of AA
  2. BBoth AA and RR are true but RR is NOT the correct explanation of AA.
  3. CAA is true but RR is false
  4. DAA is false but RR is true

Correct answer

C. AA is true but RR is false

Step-by-step solution

Phenolphthalein, (C20H14O4)( {C}_{20}{H}_{14}{O}_{4} ), 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 8.58 . 5 and attains a pink to deep red hue above pH 9.09 . 0.

Phenolphthalein dissociate in basic medium

HPh(aq)(colourless)⇌H++Ph−(Pink)\mathop{HPh\left(aq\right)}_{\left(colourless\right)} ⇌ {H}^{+} + \mathop{{Ph}^{-}}_{\left(Pink\right)}

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