Hydronium Ion and Water Autoionization

Learning Goals

You will learn more about some of the unusual properties of water including the formation of the hydronium ion and how water can autoionize.


Water is a very unusual substance in many ways. One of its unusual properties is that it can autoionize to form both an acid and a base as we hope you showed in working the above review questions. The automatic ionization occurs as one water molecule reacts with another to form the hydronium ion (H3O+) and the hydroxide ion: 2 H2O(l) --> H3O+(aq) + OH-(aq). This is a very weak reaction, meaning that the reaction is not very product favored. However, this ieaction is very important in understanding some of the properties of water.

Discussion Questions for Bulletin Board Activities

Do any other compounds autoionize? Do an internet search on autoionization and share any insights you gain with the class via the WebCT bulletin board.


Web Author: Dr. Leon L. Combs
Copyright 2000 by Dr. Leon L. Combs - ALL RIGHTS RESERVED