equivalencepointin

The equivalence point, often called the stoichiometric point, is the stage in a titration where the amount of titrant added has reacted completely with the analyte in exact stoichiometric proportions. At this point, the chemical reaction between the titrant and the analyte is theoretically complete, and no excess reactant remains.

In practice, the equivalence point is not directly observable with the naked eye. Instead, a detectable signal such as a pH change, color change of an indicator, or a signal from an instrument marks the endpoint. The endpoint is not always identical to the equivalence point, so carefully chosen indicators or instrumental methods are used to minimize offset between the two.

The pH or potential at the equivalence point depends on the type of titration. In a strong acid–strong base titration, the equivalence point occurs near pH 7. In titrations involving weak acids or weak bases, the pH at equivalence shifts away from neutral, reflecting the conjugate species present after reaction.

Methods to locate the equivalence point include monitoring pH with a calibrated pH meter to produce a sharp inflection on a titration curve, or using indicators and other instrumental approaches such as potentiometry, conductometry, or spectrophotometry. Calculations rely on stoichiometry: the moles of titrant added equal the moles of analyte times the reciprocal of the reaction’s stoichiometric coefficient.

Equivalence points are fundamental for quantitative analysis, enabling determination of unknown concentrations and assessment of sample purity. They are central to routine laboratory titrations across chemistry, biochemistry, environmental science, and clinical applications.