The key difference between complexometric and redox titrations is that complexometric titrations involve the formation of a complex ion from a simple ion and a colour change in the sample solution at the equivalence point, whereas redox titrations involve the reduction or oxidation of the sample solution at the equivalence point.
There are several differences between complexometric and redox titrations; method of titration, endpoint detection and applications are some of the criteria where they become different from each other.
CONTENTS
1. Overview and Key Difference
2. What is a Complexometric Titration
3. What is a Redox Titration
4. Complexometric vs Redox Titration in Tabular Form
5. Summary – Complexometric vs Redox Titration
What is a Complexometric Titration?
Complexometric titration is a type of titration technique where a formation of a coloured complex occurs that is helpful in determining the endpoint of a titration. It is a type of volumetric analysis. This type of titration is particularly important in determining a mixture of different metal ions in a solution because metal ions tend to form complexes.
Figure 01: Complexometric Titration
We need to use an indicator that is capable of producing a visible colour change in the solution. The complexometric reactions that take place in these titrations include the conversion of a simple ion into a complex ion, and a metal indicator or electrometrical methods can also be used as indicators. The most common types of complexometric titrations are EDTA titrations, which involve the chelation of metal ions using EDTA.
When considering the uses of complexometric titrations, it is useful for the estimation of the amount of hardness in water in the pharmaceutical industry to determine the metal concentration of drugs, in the determination of titanium dioxide content in cosmetic products, etc.
What is a Redox Titration?
Redox titrations are a type of titration technique that involves a reducing agent and an oxidizing agent. These titrations typically involve a redox indicator or a potentiometer. Moreover, there are different types of redox titrations that are named according to the titrant used in the titration. Examples include bromometry (which use bromine as the titrant), cerimetry (uses cerium(IV) salts as the titrant), dichrometry (uses potassium dichromate as the titrant), iodometry (uses iodine as the titrant), and permanganometry (uses potassium permanganate as the titrant).
For the evaluation of redox titration, we need to understand the shape of the titration curve of redox titration. For example, in acid-base titrations and complexometric titrations, the titration curve shows the change of hydronium ion concentration in the form of pH change or the change of a particular ion upon the addition of the titrant. But in redox titrations, we need to monitor the potential of the titration reaction rather than the concentration of the ionic species.
Using a reasonably approximated titration curve, we can identify the relationship between the equivalence point and the endpoint of redox titration. However, we can get the equivalence point if we react to the stoichiometrically equivalent amounts of titrant and titrand. But a variety of methods exist for the determination of the endpoint, e.g. use of indicators or sensors that respond to the change of the conditions of the sample solution. The most accurate method of finding the endpoint of the redox titration is the potentiometric titration, where we can monitor the change in potential upon the addition of titrant to the titrand. There, we can visually examine the endpoint of the titration curve.
What is the Difference Between Complexometric and Redox Titration?
The key difference between complexometric and redox titrations is that complexometric titrations involve the formation of a complex ion from a simple ion and a colour change in the sample solution at the equivalence point, whereas redox titrations involve the reduction or oxidation of the sample solution at the equivalence point. There are several other differences between complexometric and redox titrations based on criteria such as the method of titration, endpoint detection and applications.
The following table presents the difference between complexometric and redox titrations in tabular form for side by side comparison.
Summary – Complexometric vs Redox Titration
The key difference between complexometric and redox titrations is that complexometric titrations involve the formation of a complex ion from a simple ion and a colour change in the sample solution at the equivalence point, whereas redox titrations involve the reduction or oxidation of the sample solution at the equivalence point.
Reference:
1. Helmenstine, Anne Marie. “Redox Titration Definition (Chemistry).” ThoughtCo.
Image Courtesy:
1. “Complexometric titration” By Alina.Popova.26 – Own work (CC BY 4.0) via Commons Wikimedia