The acidity of carboxylic acids can vary depending on the substituents attached to the molecule. Substituents can have either electron-withdrawing or electron-donating effects, which can influence the acidity of the carboxylic acid. In general, the more electron-withdrawing the substituent, the stronger the acid, and the more electron-donating the substituent, the weaker the acid.Acetic acid CH3COOH and benzoic acid C6H5COOH are both carboxylic acids, but they have different substituents. Acetic acid has a methyl group CH3 attached to the carboxyl group, while benzoic acid has a phenyl group C6H5 attached to the carboxyl group.The phenyl group in benzoic acid is an electron-withdrawing group due to its resonance effect. The electrons in the phenyl ring can delocalize into the carbonyl group, which stabilizes the negative charge on the conjugate base benzoate ion after the carboxylic acid loses a proton H+ . This stabilization of the conjugate base makes it easier for benzoic acid to lose a proton, making it a stronger acid.On the other hand, the methyl group in acetic acid is an electron-donating group due to its inductive effect. The electron-donating effect of the methyl group destabilizes the negative charge on the conjugate base acetate ion after the carboxylic acid loses a proton. This destabilization makes it more difficult for acetic acid to lose a proton, making it a weaker acid compared to benzoic acid.In conclusion, benzoic acid is a stronger acid than acetic acid due to the electron-withdrawing effect of the phenyl group, which stabilizes the conjugate base and makes it easier for the carboxylic acid to lose a proton.