We know that in case of halogens, inductive effect is more dominant than resonance effect. So, the Cl on the para position will withdraw electrons by a -I effect and should make p-chlorobenzoic acid more acidic than benzoic acid. But why is it not so? Am I missing something?
Where are you getting your information ? So far as I can find 4-Cl-benzoic acid has a pKa of 3.98 and benzoic is 4.2.
No! -COOH is meta directing group and hence it isn't stabilised at the para position. Hence benzoic acid is more acidic than para-chloro benzoic acid(because the resonating structure of benzoic acid is more stable than p-chloro benzoic acid due to the reason mentioned above).