What is the molecular state of hypochlorous acid critically affected by pH levels?

The molecular state of hypochlorous acid is significantly influenced by pH levels, particularly in terms of its ionization. At a pH of around 7.2, hypochlorous acid exists as approximately 62% in its molecular form (HOCl) and the remaining percentage exists as its ionized form (OCl⁻). This is due to the equilibrium between these two forms shifting with changes in pH.

When the pH decreases, the concentration of hydrogen ions in the solution increases, which can drive the equilibrium toward more of the molecular form of hypochlorous acid. Conversely, as the pH increases, the proportion of the ionized form increases as the acid loses protons. Therefore, knowing that at a neutral pH (which is close to 7.2) about 62% of hypochlorous acid remains in its undissociated state provides valuable insight into its effectiveness as a disinfectant. This knowledge is crucial for environmental health professionals when determining effective concentrations for water treatment or disinfection processes.