Content Curator
Endpoint and equivalence point are two different terms used in titrations in analytical chemistry. The volumetric analysis of a sample is referred to as titration. Titration is the volumetric analysis of a given sample by the addition of a known amount of another substance known as the titrant. Titration is typically used to determine the unknown concentration of a sample or analyte. Endpoints and equivalence points are two distinct stages in the titration process.
| Table of Content |
Key Takeaways: Titration, Endpoint, Equivalence point, Volumetric analysis, Difference between endpoint and equivalence point
Read More: Number of Moles Formula
Endpoint Definition
[Click Here for Sample Questions]
The endpoint appears shortly after the chemical reaction reaches equivalence. The endpoint denotes the completion of the chemical reaction via a change in color or intensity. To obtain the endpoint clearly, a suitable indicator in the recommended quantity must be added.
A phenolphthalein indicator is used in the titration of NaOH and HCl. In acidic solutions, phenolphthalein is colorless, whereas in basic solutions, it turns pink. The solution remains colorless when the acid-base titration of NaOH and HCl reaches the equivalence point. When one or two drops of NaOH are added, the solution becomes slightly basic. The color of the phenolphthalein indicator changes to pink as soon as the solution becomes basic. The endpoint is the point in the titration where the color change is visible. As a result, the endpoint can be defined as a stage indicating the completion of the titration reaction via a color change.
Read More: Relation between Normality and Molarity
Equivalence Point Definition
[Click Here for Sample Questions]
Titration of sodium hydroxide and hydrochloric acid, for example. One mole of sodium hydroxide reacts chemically with one mole of hydrochloric acid to produce salt and water. NaOH + HCl NaCl + H2O. Sodium hydroxide (titrant) is gradually added to a sample containing hydrochloric acid and a suitable indicator during the titration process. The sodium hydroxide begins to react with the hydrochloric acid in the sample. When enough sodium hydroxide has been added to the sample to react with all of the hydrochloric acid, the equivalence point is reached.
The following describes the nature of the sample at three different stages of titration. Before reaching the equivalence point - If the equivalence point is not reached, the sample will remain acidic due to the presence of excess hydrochloric acid.
Read More: Gay-Lussac’s Law
Difference between Endpoint and Equivalence point
[Click Here for Sample Questions]
The difference between endpoint and equivalence point are:
| Endpoint | Equivalence Point |
|---|---|
| An endpoint is a titration stage that indicates the completion of the titration by a change in the color or intensity of the solution. | The titration stage at which the concentrations of titrate and titrant are chemically equivalent is referred to as the equivalence point. |
| The reaction's endpoint appears immediately after it reaches the equivalence point. Depending on the pH, the endpoint and equivalence point may occur concurrently in some cases. | The equivalence point is usually a few milliseconds before or almost at the endpoint. |
| There is only one endpoint in a chemical reaction. The appearance of the endpoint indicates that there will be no further chemical reaction. | There may be multiple equivalence points in a single chemical reaction. This scenario is particularly evident in the case of polyprotic acids containing a large number of hydroxyl (OH) ions. |
| Weak acids have a single endpoint. | Weak acids typically have a large number of equivalences. |
| The endpoint is always indicated by a change in the solution's color or intensity. | A color change may or may not always indicate the equivalence point. |
Things to Remember
- Titration is a technique used in analytical chemistry to determine the concentrations of acids, bases, reductants, oxidants, and other species.
- In a titration, a point of equivalence is the point at which the added titrant is chemically equivalent to the sample analyte.
- Endpoint, on the other hand, is a point at which the symbol changes color.
- The primary distinction between equivalence and endpoint is that the equivalence point is the point at which the chemical reaction terminates, whereas the endpoint is the point at which the color change occurs in a system.
Read More:
Sample Questions
Ques. Define Titration and mention the principle of volumetric analysis. (2 marks)
Ans: Titration is the process of adding one solution from the burette to another in the titration flask in order to complete the chemical reaction.
Volumetric analysis determines the concentration of a solution by allowing a known volume of it to quantitatively react with another solution of known concentration.
Ques. What is the difference between primary and secondary standard substances? (2 marks)
Ans: A substance is considered a primary standard if it has a high degree of purity, is stable and unaffected by air, does not gain or lose moisture in air, is readily soluble, and its solution in water remains stable for an extended period of time.
A substance that lacks the above characteristics, on the other hand, is referred to as a secondary standard substance. Crystalline oxalic acid, anhydrous Na2CO3, Mohr's salt, and other primary standards are used.
Ques. What is the difference between acidimetry and alkalimetry? Can oxalic acid solution in the burette and sodium hydroxide solution in the titration flask be used together? What, if any, limitations are there to doing so? (2 marks)
Ans: It is a branch of volumetric analysis that involves the chemical reaction of an acid and a base.
No, because when a sodium hydroxide solution is added to the titration flask, the end point color changes from pink to colorless. The precision in noting this change may be reduced as the compound changes from colorless to pink.
Ques. What is a normal solution? Why must the burette and pipette be rinsed with the solution with which they are filled? (2 marks)
Ans: A normal solution is one that contains one gram-equivalent of the solute per liter. This is represented by the symbol 1 N. The burette and pipette are rinsed with the solution with which they are filled to remove any substance that might stick to their sides and reduce the volume of liquids to be taken in them.
Ques. What is the difference between an endpoint and an equivalence point? What is the procedure for making sodium carbonate extract? (2 marks)
Ans: The end point is the point at which the indicator changes color to indicate that the reaction has completed. The point at which stoichiometric amounts of the two reactants have been added is referred to as the equivalence point. The visible endpoint may or may not coincide with the equivalence point.
The salt is combined with twice as much solid Na2CO3 and about 20 mL of distilled water. It is then boiled until it is reduced to one-third of its original volume and filtered. The filtrate is either sodium carbonate extract or a mixture of the two (S.E.).
Ques. What exactly is qualitative analysis? Explain the value of preliminary tests in qualitative analysis. (2 marks)
Ans: The type of analysis that deals with methods for determining the constituents of a compound. Preliminary tests can sometimes provide accurate information about an ion in salt. The presence of sodium, for example, is indicated by a golden yellow color in a flame test. Brown residue in a charcoal cavity test indicates the presence of cadmium in a salt, for instance.
Ques. Why should weights not be lifted by hand, and why is the balance's front door closed during weighing? What is the purpose of blue glass in the flame test? (2 marks)
Ans: This leads to weighing errors because some matter may be transferred from the hand to the weight. Opening the front door causes vibrations in the pan as a result of the operator's breath or air currents, resulting in inaccurate results.
In some cases, blue glass can absorb a portion or all of the colored light. As a result, when viewed through blue glass, the flame appears to be a different color. This aids in the identification of some fundamental radicals.
Read More:
Comments