Although his definition was limited, it certainly was a giant step in the study of chemistry. His work was eventually recognized with the 1903 Nobel Prize in chemistry. Many acids release only a single hydrogen ion per molecule into solution. Such acids are called monoprotic. Examples include hydrochloric acid, HCl, and nitric acid, HNO 3 .
Diprotic acids can release two hydrogen ions per molecule.
H 2 SO 4 is an example. Triprotic acids, like H 3 PO 4 can release three hydrogen ions into solution. The three hydrogen atoms in the acetate ion do not act as acids. Although the Arrhenius definitions of acids and bases are simplest and most useful, they are not widely applicable. Also, the Arrhenius definition assumes the acid-base reactions are occurring in aqueous solution.