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:
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✓ Correct
- (D)A is false but R is true
Answer: (C)
Solution
Assertion A is correct: Phenolphthalein is colorless in acidic solution and pink in basic medium. However, Reason R is false: Phenolphthalein is a weak acid that DOES dissociate in basic medium. The dissociation equilibrium shifts to the right in basic conditions, producing the pink-colored phenolate ion (). Therefore, A is true but R is false.
JEE Main · 2022 · 26 Jul 2022 · Shift 2 · Single correct option