During titration the point at which the added titrant is chemically equivalent to the analyte in the sample is called equivalence point. Equivalence point. The point in the titration process where the chemical reaction in the titration mixture ends is called equivalence point. The point in the titration process which is indicated by color change of the indicator is called endpoint.
It is the point where the analyte has completely reacted with the titrant. It is not always indicated by color change of the reaction mixture. It is always indicated by the color change of the reaction mixture. It gives the point where reaction ends. It comes either almost with endpoint or before the endpoint. Equivalence point in acid-base titration signals the completion of the reaction where the number of moles of the titrant and the analyte are equal as in the chemical equation.
This point must be attained accurately by administering a number of drops of the standard solution to the unknown concentration. A pipette is usually used to pour drops of the titrant into the measuring flask where the analyte has been poured with a certain indicator.
Indicators are important in acid-base titrations to clearly see the equivalence and endpoints. Acid and base titration can occur between a strong base and weak base; strong base and weak acid; strong base and strong base; or weak polyprotic acids. A different indicator may be used depending on the typical of solution being used for titration. If the pH of the titrant corresponds with the pH at equivalence point, the endpoint and equivalence point can occur simultaneously.
The picture below gives a clear understanding of titration set up in order to reach the equivalence point and then later reach the endpoint when the color changes. At first, the solution with the unknown concentration is poured with the indicator. Then the titrant is added using the burette by controlling the drops with the valve. Endpoint comes after the equivalence point in titrations. It indicates that the equivalence point has been achieved. This endpoint is indicated by the change in color of the solution.
See the picture below:. Image Courtesy: Chemistry LibreTexts. To reach the endpoint, the amount of drops should be administered carefully because a single drop can change the pH of the solution. In situation where the endpoint has been passed, a Back Titration or reverse titration can be performed depending on the nature of the solution. If too much of the titrant has been poured, the endpoint might be passed.
The solution will be to add another solution of a different reactant in excess. Indicators are not always used in titrations. The pH meters can be used to read the pH as an indication that the reaction is complete. In a strong base and acid, a pH of 7 indicates that the reaction is complete. The color change is, however, a convenient way to monitor the endpoint hence the indicators are often used. Simon Moore. Oct 28, They are similar but not identical Explanation: Equivalence point is the point where equal number of moles of acid and the number of moles of base that have been mixed together are equal.
End point is the point at which the indicator being used in such a reaction changes colour. Related questions How do you do acid base titration calculations? How do you use titration calculations to find pH? What is a redox titration and what is it used for?
Why is titration used when standardizing a solution? Is titration suitable for sodium nitrate? How can I do redox titration calculations?
0コメント