Acid strength refers to the tendency of an acid, symbolised by the chemical formula HA, to dissociate into a proton, H+, and an anion, A−. The dissociation of a strong acid in solution is effectively complete, except in its most concentrated solutions. Acid strength refers to the tendency of an acid, symbolised by the chemical formula HA, to dissociate into a proton, H+, and an anion, A−. The dissociation of a strong acid in solution is effectively complete, except in its most concentrated solutions. Examples of strong acids are hydrochloric acid (HCl), perchloric acid (HClO4), nitric acid (HNO3) and sulfuric acid (H2SO4).