What is diprotic acid?

A diprotic acid is a type of acid that can donate two protons (H⁺ ions) per molecule when it undergoes ionization in water or another suitable solvent. The term "diprotic" indicates that the acid has two dissociable hydrogen ions. The ionization process occurs in stages, with each stage corresponding to the loss of one proton.

Diprotic acids typically have two ionizable hydrogen atoms (H) in their chemical structure, which can be sequentially removed as the acid dissolves in water. As a result, diprotic acids exhibit two distinct acid dissociation constants (K₁ and K₂), which represent the degree of ionization for each proton removal step.

Examples of diprotic acids include sulfuric acid (H₂SO₄), carbonic acid (H₂CO₃), and oxalic acid (H₂C₂O₄). When these acids dissolve in water, they release the first proton to form a monovalent anion (e.g., HSO₄⁻ for sulfuric acid). Further ionization leads to the loss of the second proton and the formation of a divalent anion (e.g., SO₄²⁻ for sulfuric acid).

The dissociation of diprotic acids is a stepwise process, and the degree of ionization depends on factors such as the acid concentration, solvent properties, and pH of the solution.