This document discusses water equilibrium and acid-base chemistry. It defines the water ion-product constant Kw as equal to the hydrogen ion concentration times the hydroxide ion concentration. For pure water at 25°C, Kw is 1.0 x 10-14, so the hydrogen and hydroxide ion concentrations are both 1.0 x 10-7 M. The document then provides examples of using Kw to calculate ion concentrations in acidic, basic, and neutral solutions and determine if they are acidic, basic, or neutral based on the relative hydrogen and hydroxide ion concentrations.