Acid-Base Indicator

Definition

An acid-base indicator is a weak acid or weak base that exhibits color change as the concentration of hydrogen (H+) ions changes in an aqueous solution. They are used in titrations to signal when all reactants have reacted (equivalence point).

Related terms

pH:

A measure of the hydrogen ion concentration in a solution; it indicates the acidity or alkalinity of a solution.

Titration:

A technique where a solution of known concentration is used to determine the concentration of an unknown solution.

Equivalence point: The point in a titration at which enough titrant has been added to react exactly with the substance in solution being titrated.