What Is a Hydronium Ion

The hydronium ion or hydronium is the name given to the H3Ocation, derived from the protonation of water. The hydronium ion is the simplest type of oxonium ion. It is produced when an Arrhenius acid dissolves in water. Hydronium is also abundant in the interstellar medium and tails of comets. Hydronium Ion and pH In chemistry, pH is calculated as the ratio of hydronium ions to hydroxide (OH-) ions. When the hydrogen ion (H) concentration is discussed, its actually hydronium. The auto-dissociation of water at equilibrium is: 2 H2O â‡Å'  OH−   H3O In pure water, the number of hydroxide and hydronium ions is equal and the pH is neutral or 7. Sources Meister, Erich; Willeke, Martin; Angst, Werner; Togni, Antonio; Walde, Peter (2014). Confusing Quantitative Descriptions of Brà ¸nsted-Lowry Acid-Base Equilibria in Chemistry Textbooks – A Critical Review and Clarifications for Chemical Educators. Helv. Chim. Acta. 97 (1): 1–31. doi:10.1002/hlca.201300321Rauer, H (1997). Ion composition and solar wind interaction: Observations of comet C/1995 O1 (Hale-Bopp). Earth, Moon, and Planets. 79: 161–178. doi:10.1023/A:1006285300913997EMP...79..161R. doi:10.1023/A:100628530091