Final answer:
The pH at which an indicator changes to its final color is called the end point, which is similar but not identical to the equivalence point, a key moment in titration when equal molar amounts of acid and base are present.
Step-by-step explanation:
The pH at which an indicator turns its final color is referred to as the end point. In most cases, this is very close to, but not exactly the same as, the equivalence point. The equivalence point is the stage in a titration when the stoichiometric amount of the base has been added to the acid, which usually results in the solution containing equal molar amounts of acid and base. During the selection of an indicator for titration, chemists choose one that will provide a sharp color change at the pH at the equivalence point to ensure accuracy in determining the end point. For instance, phenolphthalein is an indicator that is colorless in its acid form and turns pink in a basic environment. Its color change occurs around a pH of 8.2-10, making it suitable for titrations with an equivalence point in that pH range.