The strength of an acid is principally a measure of its dissociative capabilities in aqueous solutions. While strong acids dissociate completely in solution, weak acids dissociates only partially.
The relative strength of an acid can be obtained from its pKa value. The pKa value is the negative logarithm of the concentration of the Ka value.
Stronger acids have a pKa value usually negative. This is a pointer to the fact that the lower the pKa value, the stronger the strength of the acid in question.
Relatively therefore, Benzoic acid is stronger than acetic acid because it has a lesser value for pKa
