Dear Student,
Acetic acid undergoes cacodyl oxide test when react with As2O3 and give bad smell of cacodyl oxide.But benzoic acid is not react with As2O3.
Benzoic acid reacts with Nahco3 or Na2so3 to give Co2 gas which will give brisk effervesence.Benzoic acid is aromatic, to give a sooty flame while acetic acid won't .Acetic acid is a pungent liquid and benzoic acid is a white crystalline flaky solid soluble in hot water. Aceti acid can dissove both polar and nonpolar copounds.
Acetic acid reacts with actaldehyde to gives positive iodoform while Benzoic acid reacts benzaldehyde does not .
Regards,