Endpoint and Equivalence Point

Titration is a technique used in analytical chemistry to evaluate the presence of acids, bases, reductants, oxidants, and other substances. Titrations may occur in a variety of processes, including redox reactions and acid-base reactions, in most cases. In the course of the procedure, two critical milestones known as the endpoint and the equivalence point are achieved. During the course of a titration, the point of equivalence is defined as the point at which the added titrant is chemically equal to the sample analyte. Endpoint, on the other hand, is the point at which the colour of the symbol changes. The primary distinction between the equivalence point and the endpoint is that the equivalence point is the point at which the chemical reaction comes to a close, while the endpoint is the point at which the colour change happens in a system or solution. 

Equivalence point

The equivalence point in acid-base titration indicates that the process has reached its conclusion when the number of moles of the titrant and the analyte are equal, as shown by the chemical equation. Using the same example, 1 mole of NaOH and 1 mole of HCl will be equivalent to precisely 1 mole of NaOH at the equivalence point in a titration of NaOH and HCl. This point must be precisely determined by delivering a certain number of drops of the standard solution to the unknown concentration in a controlled environment. A pipette is often used to transfer small amounts of the titrant into the measuring flask, into which the analyte has been poured along with a specific indicator. When doing acid-base titrations, it is critical to use indicators to clearly observe the equivalence and endpoints. 

Titration of acids and bases may occur between a strong base and a weak base, between a strong base and a weak acid, between a strong base and a strong base, or between weak polyprotic acids. Depending on the kind of solution being used for titration, a different indicator may be used. As an example, while doing a NaOH and HCl titration, the phenolphthalein indicator is employed, but when performing an NH3 and HCl test, the methyl orange indicator is more appropriate. If the pH of the titrant is the same as the pH at the equivalence point, the endpoint and the equivalence point might occur at the same time in the same experiment. 

Take, for example, the titration of sodium hydroxide and hydrochloric acid, which is an acid-base interaction in nature. One mole of sodium hydroxide interacts with one mole of hydrochloric acid to produce salt and water in a chemical reaction, according to the formula. 

HCl + NaOH NaCl + H2O

A solution of sodium hydroxide (titrant) is progressively added to a sample containing hydrochloric acid and a suitable indicator over the course of the titration procedure. In this case, the sodium hydroxide begins to react with the hydrochloric acid already present in the sample. At the equivalence point, sufficient sodium hydroxide has been added to the sample for it to react with all of the hydrochloric acid present in the solution. 

Endpoint

In titrations, the endpoint is the point that occurs after the equivalence point. It signifies that the point of equivalence has been reached in the equation. The change in hue of the solution indicates the presence of this endpoint. 

The quantity of drops delivered to achieve the endpoint should be calculated carefully since even a single drop might cause the pH of the solution to alter. In the event that the endpoint has been reached, a Back Titration or a Reverse Titration may be done, depending on the nature of the solution being investigated. If an excessive amount of titrant is poured, it is possible that the endpoint will be exceeded. Addition of another solution containing a different reactant in excess will provide a solution. 

Titrations do not usually include the use of indicators. The pH metres may be used to read the pH of the solution as an indicator that the reaction has completed successfully. A pH of 7 shows that the reaction is complete in the presence of a strong base and acid. It is true that the colour change is a handy approach to monitor the endpoint, which is why the indicators are often used. When a solution of sodium chloride and hydrochloric acid becomes pink, the solution has reached its endpoint, as shown by the phenolphthalein indicator. The endpoint does not always represent the conclusion of the reaction, but rather the completion of the titration. 

The endpoint of a chemical reaction emerges shortly after the process has reached equivalence. The endpoint, which is indicated by a change in colour or intensity, shows that the chemical process has reached its conclusion. In order to get a clearly defined endpoint, a relevant indication must be included in the given amount. 

When titrating NaOH and HCl, a phenolphthalein indicator is employed to monitor the reaction. In the presence of acidic solutions, phenolphthalein is colourless, but it becomes pink in the presence of basic solutions. When the acid-base titration of NaOH and HCl reaches the point of equivalency, the solution continues to be colourless despite the presence of a base. When one or two drops of NaOH are added to the solution, the solution becomes somewhat basic. The colour of the phenolphthalein indicator changes from blue to pink as soon as the solution becomes basic. The endpoint of a titration is the stage of the titration at which the colour change may be seen. 

As a result, it can be inferred that the endpoint is a step that indicates the conclusion of the titration process by the use of a change in colour. 

Conclusion

In chemical titrations, the words endpoint and equivalence point are the most often seen. The majority of the time, both words are used interchangeably and are considered to be synonymous. Titrations are characterised by the presence of two distinct concepts: the endpoint and the equivalence point. Science is a complicated system that provides an understanding of the world, including an understanding of things that cannot be seen with the naked eye. Compared to what is evident to the untrained eye, things are more convoluted and difficult to understand. Science provides explanations for a variety of issues that are not only established in a practical manner but also in an abstract one.