Question

Which equation represents the reaction of a weak acid with water? HCl + H2O H3O+ + Cl- HCO3– + H2O H2CO3 + OH– H2O H + + OH- HCOOH + H2O H3O+ + HCOO-

Answer 1

OH- HCOOH + H2O is the answer

Answer 2

HCOOH + H2O ↔ H3O+ + HCOO-

Step-by-step explanation:

A strong acid is one which completely dissociates into its corresponding ions in aqueous medium.

In contrast, a weak will only partially dissociate such that there is an equilibrium between the dissociated ions and the undissociated acid.

In the given examples:

HCl, HCO3- and H2CO3 are all strong acids. However, HCOOH i.e. formic acid is a weak acid which dissociates in water to form H3O+ and formate ion, HCOO-

HCOOH + H2O ↔ H3O+ + HCOO-