Chapter 6, Lesson 9 Multimedia
Neutralizing an Acidic Solution

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The acidic solution has a greater concentration of H3O+ ions than OH- ions. When a base is added, it accepts protons from water molecules, creating more OH- ions. The H3O+ ions and indicator molecules donate protons to the OH- ions. This lowers the concentration of H3O+ ions toward neutral and changes the color of the indicator.