hydroniumionin
The hydronium ion, with the chemical formula H3O+, is the positive ion formed when a proton (H+) attaches to a water molecule in aqueous solutions. It is the conjugate acid of water and a central species in acid–base chemistry of water-based systems. In typical acid–water chemistry, acids donate protons to water, producing hydronium ions according to reactions such as HA + H2O ⇌ A− + H3O+. The hydronium ion is largely responsible for the acidic character of a solution, and its concentration determines the pH: pH = -log10 [H3O+].
The autoprotolysis (autoionization) of water, 2 H2O ⇌ H3O+ + OH−, sets the relationship between hydronium and hydroxide
Structure and solvation are often summarized by describing H3O+ as a water molecule with an added proton,
Hydronium ions occur in all aqueous acids and play a fundamental role in driving many chemical, biological,