Question

Assertion :Benzoic acid is stronger acid than acetic acid. Reason: $K_a$ for benzoic acid is $6.5\times {10}^{-5}$ and for acetic acid is $1.74\times {10}^{-5}$.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Acidic means - it depends H+ dissociation and the formation of conjugate anion.

$C_6{H}_5-COOH+H_{2}O\to C_6{H}_5-CO{O}^{-}+H_3{O}^{+}$

$C{H}_{3}COOH+H_{2}O\to C{H}_{3}CO{O}^{-}+H_3{O}^{+}$

In acetic acid, Methyl group is electron releasing group, so the formation of conjugate acetate anion is less when compare to benzoate anion.

Because phenyl is electron withdrawing group, it pulls the electron from carboxyl group.

Ka value for benzoic acid is $6.5\times {10}^{-5}$ and for acetic acid is $1.74\times {10}^{-5}$.

Hence, Benzoic acid is more acidic than acetic acid.