In titrations of acids and bases, what is the difference between the end point of the titration, and the equivalance point? Also, what is chemically occuring during the buffer zone? Thanks!
Good question and one that students sometimes have trouble with. The equivalence point is where the stoichiometry and chemistry indicates that the materials being titrated have exactly neutralized each other (in the case of acid and bases). The END point is where some arbitrarily chosen indicator tell us that we have finished the titration. We TRY to use an indicator which will turn at the equivalence point but most are not exactly at the equivalence point. Of course the pH at the equivalence point changes as we change the titrant and the material being titrated.
The pH changes for acid/base titrations as we change acids/bases. Redox titrations also have equivalence points and we try to use an indicator that has the E(voltage) value that is the same as that of the equivalence point.
To determine the end point of a titration, we typically use an indicator that changes color when the reaction is near completion. This indicator may not always perfectly correspond to the equivalence point, which is the point at which the reactants have completely reacted with each other in stoichiometric proportions.
During the buffer zone, the pH of the solution changes gradually as the concentration of the titrant increases or decreases. In this zone, the solution acts as a buffer, which means it is able to resist changes in pH when small amounts of acid or base are added. This is due to the presence of a weak acid and its conjugate base (in the case of an acidic buffer) or a weak base and its conjugate acid (in the case of a basic buffer) in the solution. The buffer zone allows for a more precise determination of the equivalence point because it helps to maintain a relatively constant pH during the titration process.