What is the strongest acid among the given compounds? 

C₆H₅COOH

The correct answer is option 2- C₆H₅COOH (Benzoic acid)

Explanation:

To determine the strongest acid, we compare the acidity (Ka or pKa values) of the given compounds. A lower pKa means stronger acid.

1. C₆H₅CH₂NH₂ (Benzylamine) – This is a weak base (amine), not an acid. It would act as a conjugate base of a very weak acid (ammonium ion). Hence, least acidic.

2. C₆H₅COOH (Benzoic acid) – A carboxylic acid directly attached to a phenyl group. Its pKa ≈ 4.2. This is reasonably strong among organic acids.

3. m-CH₃C₆H₄COOH – This is meta-methylbenzoic acid. The CH₃ group is electron-donating, but at meta-position, its inductive effect is minimal. So it is slightly less acidic than benzoic acid.

4. p-CH₃C₆H₄COOH – This is para-methylbenzoic acid. Here, the CH₃ group shows both inductive (electron-donating) and resonance effects. Overall, it decreases acidity more than the meta-position.

Conclusion:

C₆H₅COOH (Option 2) is the strongest acid among the given options, as alkyl groups (like CH₃) tend to reduce acidity, and amines are basic.