Equivalencepunt

Equivalencepunt, or equivalence point, is a concept in titration describing the moment when the reacting quantities of titrant and analyte have reached a stoichiometric balance. At this point, the amount of titrant added corresponds exactly to the amount required by the reaction to convert the limiting reagent into product, assuming complete reaction.

In acid–base titrations, the equivalencepunt occurs when aA + bB → products has consumed the reagents in the fixed ratio a:b. If the analyte has concentration CA and volume VA and the titrant has concentration CB, the equivalence condition is a CA VA = b CB VB. For a simple strong acid–strong base titration (a = b = 1), VB(eq) = CA VA / CB. In cases involving weak acids or bases, the pH at the equivalencepunkt may differ from 7; weak acid–strong base titrations typically yield pH greater than 7, while strong acid–weak base titrations yield pH less than 7. Polyprotic acids or bases can have multiple equivalencepunkte corresponding to successive neutralizations.

Detecting the equivalencepunkt can use pH measurements, conductivity, or potentiometric methods, as opposed to the endpunkt indicated by a color change of an indicator. The endpunkt should align closely with the equivalencepunkt, but indicators introduce a small offset because their color transition occurs over a pH range rather than at a precise point.

In other titration types, such as redox or complexometric titrations, the equivalencepunkt similarly marks the complete reaction between reactants, reinforcing its role as the quantitative endpoint for stoichiometric analysis.