How does the titrator recognize that neutralization is achieved and the equivalence point has been reached? For titrations to be of any practical value there must be some way for the equivalence point to be detected. Indicators are selected that change color near the equivalence point. (It is possible to estimate the equivalence point for most titration.) In a titration the point at which an indicator changes color is called the endpoint of the titration. Ideally,the endpoint and the equivalence point should be the same.
For the titration of HCl with NaOH, the equivalence point will occur at a pH of 7, since the products of the titration, NaCl and H2O, form a neutral solution. However, as this titration proceeds with the addition of standard base, an abrupt pH change begins at a pH of 4 and increases steeply to a pH of about 10 with the addition of less than a single drop of standard base, which means that the volume of standard base added is essentially the same anywhere within this 6-unit pH range.