Assertion (A): Benzoic acid gives brisk effervescence with aqueous NaHCO3, whereas phenol does not. Reason (R): Phenol is a stronger acid than carbonic acid. Choose the correct option.

Both A and R are true, but R is not the correct explanation of A

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

JEE Advanced levelSingle correct optionDifficulty 3 of 3si007

Assertion (A): Benzoic acid gives brisk effervescence with aqueous $NaHCO X_{3}$ , whereas phenol does not. Reason (R): Phenol is a stronger acid than carbonic acid. Choose the correct option.

Benzoic acid (

p K_{a} \approx 4.2

) is stronger than carbonic acid (

p K_{a 1} \approx 6.4

) and liberates

CO X_{2}

from bicarbonate. Phenol (

p K_{a} \approx 10

) is weaker than carbonic acid, so it does not. Hence A is true but R is false.