Chemistry - GOC Question with Solution | TestHub

An ortho OH group stabilises the carboxylate anion through intramolecular hydrogen bonding (in addition to its -I effect), so salicylic acid (b) is much stronger than benzoic acid (a) (pKa 2.97 vs 4.20). With hydroxyl groups on both ortho positions, the anion of (c) is chelated on both sides and stabilised still further (pKa ≈ 1.3). Hence c $>$ b $>$ a.