What is the function of an indicator in an acid-base titration?

An indicator plays a crucial role in an acid-base titration by providing a visual signal that marks the endpoint of the titration. This signal typically manifests as a color change that occurs at a specific pH range, allowing the person conducting the titration to easily identify when the reaction between the acid and base is complete. Different indicators are chosen based on the pH range at which the color change occurs, ensuring accuracy for the specific acid and base being titrated.

Indicators do not determine the molarity of the solution directly; instead, they help visualize the completion of the reaction, after which the molarity can be calculated based on the volume of titrant used. They also do not neutralize the acid or react with the solute in a way that impacts the titration results; rather, their sole function is to indicate the pH at which the reaction reaches the equivalence point. Thus, the primary value of an indicator lies in its ability to change color when the pH of the solution shifts to a certain level, marking the transition from acidic to basic or vice versa.