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Difference Between Endpoint and Equivalence Point - Endpoint, Equivalent Point, Differences, Practice Problems and FAQ

What breakfast food could be tastier than a fresh piece of buttered toast?

If you don't like having to wait for your bread to brown while standing by the stove, an electric toaster can be the ideal answer for you.

However, how will it work?

Watch the provided GIF. When the bread is first inserted, it is fully lowered by pressing the black lever; the indicator light turns green. When the indicator light goes red, your toast is ready.

Please enter alt text

What does this have to do with the concept discussed on this page?

There is a connection! Similar to when the indicator light turns red, the endpoint of a titration is the point at which it is finished.

Wait, what? That is known as the equivalence point, isn't it? Is the equivalence point the same as the endpoint?

Keep your inquiries to a minimum since that is the subject of this concept page. Without further ado, let's get to know about endpoint and equivalence point.

TABLE OF CONTENTS

  • Foundation
  • Equivalence Point
  • Endpoint
  • Difference Between Endpoint and Equivalence Point
  • Practice Problems
  • Frequently Asked Questions - FAQ

Foundation

The two terms that are most frequently used in chemical titrations are endpoint and equivalence point. These words are frequently interchanged and taken to mean the same thing. Both endpoint and equivalence point are distinct ideas that resemble each other. The purpose of this essay is to clarify the key distinctions between the concepts of endpoint and equivalence point.

Let's recap titrations briefly before moving on to the point. Titration is the process of doing a volumetric analysis on a sample by adding a given quantity of a titrant. Titration is typically conducted in order to determine the given sample's or analyte's unknown concentration. The titration procedure typically has two stages: the endpoint and the equivalency point. An equivalence point is a point at which the combined moles of two solutions equilibrate. It denotes that the titrant amount applied is chemically comparable to the sample in question. The endpoint comes after the equivalence point. An endpoint is a stage where a colour or intensity shift indicates the reaction has finished.

In acid-base reactions, equivalence points and endpoints are frequently seen. To obtain a better understanding of them, let's dig a little deeper into each of them.

Equivalence Point

Let's take the titration of sodium hydroxide and hydrochloric acid, which is an example of an acid-base reaction. Salt and water are produced chemically when one mole of sodium hydroxide combines with one mole of hydrochloric acid.

HCl+ NaOHNaCl +H2O

The titrant in this titration is sodium hydroxide. It is slowly added to a mixture of hydrochloric acid and an appropriate indicator, which is the sample. The hydrochloric acid in the sample and sodium hydroxide begins to react. An equivalence point is reached when enough sodium hydroxide has been introduced to cause all of the hydrochloric acid to react.

Below is a list of the characteristics of the sample at each of the three titration phases.

  1. Before Equivalent Point: The sample remains acidic as long as the equivalence point is not reached because there is too much surplus hydrochloric acid present.
  1. At Equivalent Point: The sample turns neutral at the equivalence point as a result of the production of salt.
  1. After Equivalence Point: After reaching the equivalence point, the sample becomes basic due to the further addition of sodium hydroxide.

The equivalence point is a point at which the molar concentration of an analyte and the titrant are chemically equivalent.

Endpoint

The endpoint of a chemical reaction appears shortly after the equivalence point is reached. With the help of a change in colour or intensity, the endpoint denotes the completion of the chemical reaction. A suitable indicator must be applied in the specified amount in order to obtain the endpoint clearly.

A phenolphthalein indicator is employed in the titration of NaOH and HCl. In the presence of basic solutions, phenolphthalein turns pink rather than exhibiting any colour. The solution is still colourless when the equivalence point of the NaOH and HCl acid-base titration is reached. The solution becomes somewhat basic upon the addition of one or two more drops of NaOH. The colour of the phenolphthalein indicator turns pink when the solution becomes basic. The endpoint of the titration is the point at which the colour changes.

The endpoint is a point at which the sample undergoes colour change, indicating the end of the titration reaction.

Difference Between Equivalence Point and Endpoint

Equivalence Point

Endpoint

The stage of a titration at which the concentrations of the titrate and the titrant are chemically equivalent is known as the equivalence point.

An endpoint is a point in a titration that signifies the completion of the titration by a change in the colour or intensity of the solution.

It usually occurs a few milliseconds prior to the endpoint.

The endpoint occurs instantly after the equivalence point. Depending on the pH, the endpoint and equivalence point may occur concurrently.

Multiple equivalence points can exist in the same chemical process. This is particularly true in the case of polyprotic acids that contain many hydroxy ions.

There is only one endpoint to a chemical reaction indicating that no reaction takes place further.

Generally, weak acids have numerous equivalent points.

Weak acids have only one endpoint.

A colour change may or may not occur during the equivalence point.

A colour change or intensity change occurs during the endpoint.

Practice Problems

1. Pick out the incorrect statement.

a. A chemical reaction has just one possible endpoint.
b. A point at which the combined moles of two solutions equilibrate is known as an equivalence point.
c. Endpoint and equivalency points are the same concepts used for titrations.
d. The moment at which the colour changes is the titration's endpoint.

Answer: C

  • There is only one endpoint corresponding to one chemical reaction and a colour or intensity change signifies it.
  • At the equivalence point, the moles of the two reacting solutions equilibrate.
  • Endpoint and equivalence points are not the same. The primary distinction between equivalence point and endpoint is that the former refers to the moment at which a chemical reaction ends, whereas the latter refers to the time at which a system's colour changes.

Hence, the statement given in option C is incorrect.

So, option C is the correct answer.

2. __________ is a step that, by changing colour, indicates the titration reaction has concluded.

a. Equivalence point
b. Analyte
c. Titrant
d. Endpoint

Answer: D

  • Equivalence point is the point at which the concentration of both the reacting solutions are equal.
  • In titrations, the sample whose concentration is to be estimated is called the analyte, and the standard solution used to estimate the analyte is called the titrant.
  • Endpoint is a step that, by changing colour, indicates the titration reaction has concluded.

So, option D is the correct answer.

3. The molar concentration at which an analyte and titrant are chemically equivalent is known as the ___________.

a. Equivalence point
b. Endpoint
c. Titration point
d. Precipitation point

Answer: A

Solution: The molar concentration at which an analyte and titrant are chemically equivalent is known as the equivalence point.

So, option A is the correct answer.

4. Pick out the incorrect statement.

a. Typically, the equivalency point happens a few milliseconds before the endpoint.
b. The endpoint and equivalency point could occur simultaneously depending on the pH.
c. The endpoint typically happens a short while before the equivalence point.
d. The point of equivalence is achieved as soon as the endpoint appears.

Answer: C

Solution: Endpoint always appears after the equivalence point. It may occur simultaneously with the equivalence point but can never occur before the equivalence point.

Hence, the statement given in option C is incorrect.

So, option C is the correct answer.

Frequently Asked Questions - FAQ

1. Why is it that pH = 7 is not usually the equivalent point?
Answer:
Since a weak acid's conjugate base is also weakly basic, the titration's equivalence point rises above pH = 7 at this point. In contrast, because only the conjugate acid is present when a weak base and strong acid are titrated, the pH at the equivalence point is lower than 7.

2. What makes titrant and titrand different from one another?
Answer: The substance in the titration buret is called a "titrant," and most of the time its precise concentration is known. The material being examined during the titration is referred to as the "titrand." It is also referred to as ‘analyte’.

3. Is the stoichiometric point the same as the equivalency point?
Answer: Yes, they are the same, In a chemical reaction, when exactly the right amounts of acid and base are present to neutralise the solution, the point is called the equivalence point or stoichiometric point.

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