Here's why:

* HCl is a strong acid, meaning it completely ionizes in water to form H+ ions and Cl- ions. This makes it a very effective proton donor.

* Benzoic acid is a weak acid, meaning it only partially ionizes in water. This is because the benzene ring in benzoic acid pulls electron density away from the carboxyl group, making it less likely to release a proton (H+).

Therefore, HCl is a much stronger acid than benzoic acid.

You can compare the acid strengths by looking at their pKa values:

* HCl: pKa ≈ -7

* Benzoic acid: pKa ≈ 4.2

A lower pKa value indicates a stronger acid.