Difference Between Equivalence Point vs Endpoint
When you are driving and you stop the car, say, at the traffic light, does that mean you have come to the end of your journey? Most likely not. The lights are there to control movements and make it easier for drivers and pedestrians alike to make use of the road without problems. That can be likened to the difference between endpoint and equivalence point.
These two are vital milestones in titration, a chemical process used to find out the properties of an unknown substance by applying a different solution of known concentration. They both occur towards the end of the process, which is a contributing factor that has made it difficult to tell the two apart.
Definition of Equivalence Point
An equivalence point can be defined as the end of the chemical reaction in a titration process. It is the first change an observer gets to notice in the process, and typically signals that the endpoint is very close.
Here are a few things you need to keep in mind about this.
- It is the stage that officially states the end of the procedure as far as chemical reactions are concerned. Other forms of changes may occur after this point, but they would not be chemical in nature.
- This stage may occur more than once in some substances, especially weak acids because they have a high level of H dissociations.
- This level also reveals that the standard solution and the analyte now have equal numbers. This is a notable revelation because it helps to determine the concentration of the unknown solution.
It is important to keep in mind that this phenomenon does not have a specific pattern of occurrence. In comparing endpoint vs equivalence point, the former (as well as spectroscopy, indicators, and conductance) plays a role in determining the latter.
The most common of them all is the change in color of self or pH halochromic chemical compound, depending on which one was used, but it is not always the case.
Definition of Endpoint
An endpoint is defined as a point in the titration process where the indicator changes color. So, as you carefully add the acid from the burette to the base in the conical flask, there will come a point where the color changes. At this stage, you are expected to take note of the volume of the content in the burette and repeat the steps two more times until you have three results that are close in agreement.
These results, if they are close in agreement, demonstrates the latter in the equivalence point vs endpoint comparison. Here are some notes to keep in mind about this.
- There may be a physical change with this event, but it does not mark the end of the procedure. It is more like a signal.
- With a weak acid, this event occurs just once, and it can come either before or after the equivalence point. There is no particular order.
- There is always a color change
Note that both solutions are usually colorless, and a halochromic chemical compound, such as Methyl orange, Methyl red, Phenolphthalein, etc., are used to facilitate the color change when the mole number for both substances match.
Main Differences Between Equivalence Point vs Endpoint
Here is a summary of the difference between equivalence point and endpoint in the table below.
|Basis of Comparison
|The end of the chemical reaction in a titration process
|A point in the titration process where the indicator changes color.
|Implies the end of the procedure
|Does not necessarily show the end of the procedure
|May, or may not show a color change
|Always signaled by a color change
|Implies complete reaction
|Does not show a complete reaction
|Can occurs more than once
Difference Between Equivalence Point and Endpoint: Conclusion
This is an exciting topic with comprehensive theoretical concepts, but it is even more exciting when put into practice. That way, the theories can be applied and it would make more sense. It is always crucial to note that color change with the latter is a big deal, unlike the former.