Question

carbonic acid gives an acidic salt but hydrochloric acid does not. why?

Answer 1

Acid salts can be formed only with neutralization of diprotic or polyprotic acids. Hydrochloric acid has only one hydrogen atom that is displaced during the reaction and therefore hydrochloric acid salts are not acidic in nature. On the other hand carbonic acid is diprotic and on neutralization it still contains one hydrogen atom that can be displaced, therefore carbonic acid salts are acidic in nature.

Answer 2

Carbonic acid is a diprotic acid. On Neautralisation it still consist of one H that can be displaced. This wont happen in mono protic acid like HCl