The point at which stoichiometrically equal amounts of acid and base have reacted.
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The equivalence point is the stage in a titration at which the moles of acid and base are exactly in the stoichiometric ratio given by the balanced equation. At this point the titrant has neutralized the analyte completely, but the resulting pH depends on the nature of the salt formed. For a strong acid with a strong base the pH is 7, while for a weak acid with a strong base the pH is above 7 because the conjugate base hydrolyses. For a strong acid with a weak base the pH is below 7 for the same reason in reverse. The equivalence point is a theoretical concept that can only be approximated experimentally.
Key ideas: The equivalence point is where moles of titrant exactly equal the stoichiometric amount of analyte. Its pH depends on the species present: 7 for strong-strong, above 7 for weak acid with strong base, below 7 for weak base with strong acid. On a curve it is the steepest point, located by the maximum of the first derivative.
Common mistakes and connections: Misconception: equivalence always equals pH 7. It is a stoichiometric concept, not a pH value. In polyprotic cases there are several. Do not confuse with the half-equivalence point where pH equals pKa. Experimentally one sees the end point instead; choose indicators to make the two coincide.
Acetic acid reaches its equivalence point above 7, near pH 8.7, because the acetate formed is a weak base that hydrolyses. The interactive lesson shows this as a live animation or chart.
Acetic acid titrated with NaOH reaches its equivalence point at a pH of about 8.7.
The point at which stoichiometrically equal amounts of acid and base have reacted.
Equivalence Point is a intermediate topic in Acids, Bases & Electrochemistry. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Acids, Bases & Electrochemistry first: pH of Salt Solutions, Acid-Base Neutralization, Titration.
The next topics in Acids, Bases & Electrochemistry are End Point and Titration Curve.
Yes. The interactive lesson includes a self-check question on Equivalence Point, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Equivalence Point is topic 23 of 105 in Acids, Bases & Electrochemistry.