Monoprotiske

Monoprotiske, in chemistry, refers to acids that can donate exactly one proton per molecule in an aqueous solution. The dissociation is described by HA ⇌ H+ + A−, where HA is the monoprotic acid and A− its conjugate base. This is in contrast to polyprotic acids, which can release two or more protons through successive dissociations (for example H2SO4 or H3PO4).

Common examples of monoprotic acids include strong monoprotic acids such as hydrogen chloride (HCl) and nitric acid (HNO3), which dissociate essentially completely in water. Weak monoprotic acids include acetic acid (CH3COOH) and formic acid (HCOOH); they have a single pKa value that characterizes their strength. The concept also applies to other monoprotic acids like benzoic acid.

In acid–base chemistry, monoprotic acids can form buffers with their conjugate bases. For a monoprotic acid, the pH near a buffer region is described by the Henderson–Hasselbalch equation: pH = pKa + log([A−]/[HA]). Because a monoprotic acid has only one dissociation step, it exhibits a single pKa value, whereas polyprotic acids show multiple pKa values corresponding to successive protons.

Etymology-wise, "monoprotiske" derives from Greek roots meaning “one proton.” The term denotes the stoichiometry of proton donation rather than the overall strength of the acid, as monoprotic acids can be either strong or weak.