Titration curves & equivalence point (article) | Khan Academy
Although Lyman () described the difference between a titration's end point ( the observed inflection point) and its stoichiometric equivalence point. The equivalence point, or stoichiometric point, of a chemical reaction is the point at which The endpoint (related to, but not the same as the equivalence point) refers to the point at which the indicator changes colour in a colourimetric titration . Endpoint and equivalence point are the two most important concepts in chemistry titrations. The technique of titrations can occur in redox.
In some reactions, there could be numerous equivalence points, especially in polyprotic acids and bases where multiple hydroxide ions exist. This article unfolds the key difference between the endpoint and equivalence point in chemical titrations.
Definition of Equivalence point 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.18.3 Sketch the general shapes of graphs of pH against volume for titrations [HL IB Chemistry]
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.
Definition of Endpoint 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: 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 point where a color change occurs is taken as the endpoint of the titration. But it is not the equivalence point of the reaction. Here, the moles of titrant should be equal to the moles of the unknown analyte.
Titration curve for a titration of an acid with a base Methods of Determining the Equivalence Point Color change of self-indicators — In reactions involving self-indicators as reactants, the color change indicates the equivalence point of the titration since indicators are not used.
Endpoint — Sometimes, equivalence point can be considered as the endpoint since they are approximately equal.
Difference Between Endpoint and Equivalence Point
Conductance — Conductance can also be used to determine the equivalence point of the titration. Here, the conductance should be measured throughout the titration, and the equivalence point is where a rapid change of conductance occurs.
This is a bit difficult method. Spectroscopy — This method can be used for colorful reaction mixtures.
The difference between 'end point' and 'equivalence point' in a titration | Yeah Chemistry
The determination is done according to the rapid change in wavelengths that are absorbed by the sample. What is Endpoint The endpoint of a titration is the point where a color change occurs. Normally, acids and bases are colorless solutions. Therefore, to determine the end of the neutralization reaction of an acid with a base, an indicator that is able to change the color of the reaction mixture with changes in pH is used.
For example, Phenolphthalein is a common indicator used in acid base reactions.
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The color change of this indicator is given at 8. But this indicator is not suitable for reactions that occur at low pH values. Therefore, the indicator should be chosen accordingly. Color of phenolphthalein at different pH values The endpoint is not the point where the total amount of the unknown has completely reacted with the titrant. In reactions where self-indicators are involved, the end point is given when the whole amount of the unknown has reacted with titrant.
Therefore, the endpoint is equal to the equivalence point here.