Hydrochloric Acid (HCl) + Water (H2O)--> Hydronium (H3O+) + Chlorine(Cl-) In this equation, Hydrochloric Acid is the acid and Water is the base. Hydrochloric Acid gives its H+ proton to water making it Hydronium. Hydronium is now the conjugate base and chlorine is now the conjugate base