HCl is a strong acid while, acetic acid is a weak acid. HCl acid ionises completely to H+ and Cl− ions. On the other hand, acetic acid dissociates partially. In an acetic acid, there is a large number of undissociated CH3COOH molecules, and just a few H+ and CH3COO−ions. Hence, dilute HCl acid is stronger than highly concentrated acetic acid