HCl(aq)+H2O(l)→H3O+(aq)+Cl−(aq) is the reaction. Hydrochloric
acid (HCl) is a strong acid and each mole of HCl donates one proton (H+) to
water, producing a hydronium cation H3O+. Ionization of hydrochloric acid leaves
behind one Cl- anion in the solution. Thus, HCl is completely ionized in
aqueous solution.
