Endpoint and Equivalence Point

Titration is a chemical process that is performed in the laboratory. It is the volumetric analysis of a given sample. This process is used to determine acids, bases, and other such chemical species. 

In a titration, two points are encountered while performing the test. These points are namely, endpoint and equivalence point. Often, these terms are used interchangeably and are considered as one. This article will discuss these points and key the difference between the two.

What is Titration?

Titration is also known as the volumetric analysis of a sample. This is so known because it deals with the volumes of the known and unknown samples. It is used to determine the concentration of the unknown sample with the help of the concentration of the known sample. Titration can be of two types: it may involve an acid-base reaction or a redox reaction.

The sample of known concentration and volume is prepared. This solution is known as the titrant. Finally, it is mixed with the sample of unknown concentration and known volume, known as the titrant. The acids-bases react and neutralize each other, giving the color that depicts the reaction’s end.

What is the Endpoint in a Titration Reaction?

The endpoint in a titration reaction is encountered when the titration reaction gets completed and a color change denotes this completion. The color change is denoted by the indicators which are added to the sample before titration. 

Let us take the most common example of the neutralization reaction.

HCl + NaOH 🡪 NaCl + H2O

In the titration of NaOH and HCl, an indicator, namely phenolphthalein, is used. Phenolphthalein remains colorless in an acidic medium and exhibits pink in a basic medium.

NaOH is filled in the burette and the solution of the HCl and phenolphthalein is taken in the beaker. Then the NaOH is added dropwise from the burette in the beaker. 

When the titration starts, the medium in the beaker is acidic. Therefore, the color of the solution remains colorless. A time comes when the solution becomes basic, and the solution turns pink. This is the point when the endpoint is achieved. 

Thus, the endpoint denoted the completion of the titration via color change. 

What is the Equivalence Point in a Titration Reaction?

When an exact amount of acid is added to the base and the reaction is neutralized, the point achieved is known as the equivalence point. 

Let us consider the same example as the previous one. The addition of sodium chloride and hydrochloric acid. When the titration starts, sodium hydroxide starts reacting with the hydrochloric acid. 

The equivalence point is attained when the molar concentration of the acid becomes equivalent to the molar concentration of the base. 

Difference Between the Endpoint and Equivalence point

Conclusion

By going through this article, we have been familiar with the process of titration, the endpoint, and the equivalence point.

Endpoint denotes the completion of the titration process by changing the color of the solution. At the same time, the equivalence point is achieved in a titration when the molar concentration of the acid becomes equivalent to the molar concentration of the base.

Thus, by reading this article, one can now be able to differentiate between the endpoint and equivalence point and will not consider it the same.