Learn about the principle, types, and applications of redox titration, which is a type of titration based on a redox reaction between analyte and titrant.
Titration is a type of quantitative chemical analysis used to determine an analyte's unknown concentration. It is also known as titrimetry referring to volumetric analysis because volume measurement is important in titration. The titrant is added from a burette until the reaction is complete, and an indicator is usually employed to signify the equivalence point or endpoint.
Titration consists of four types based on the different procedures and goals such as including acid-base, complexometric, precipitation, and redox titration.
What is redox titration explain with example?
A redox titration is called oxidation-reduction titration it is an oxidation-reduction process that takes place between an oxidizing and a reducing agent. In this type of titration, a chemical reaction occurs with the transfer of electrons to the reactant ions of aqueous solutions. 
In the oxidation-reduction titration process, an oxidizing compound is titrated with the standard solution of the reducing agent, or a reducing compound is titrated with a standard solution of an oxidizing agent.
It is used for the analysis of organic solutes and generally evaluating chlorination. In an oxidation-reduction (redox) titration, generally, a potentiometer or redox indicator solution is used.
Treating an iodine solution with a reducing agent to form iodide while using a starch indicator to aid determine the endpoint of the titration is the most common example of redox titration.
What is the principle of redox titration?
The principle involved in oxidation-reduction (Redox titration) is that the oxidation process involves the loss of electrons while the reduction process involves the gain of electrons.
Oxidant + ne ↔ Reductant
The following are the key characteristics of redox reactions which consist of both oxidation and reduction reactions.
Oxidation reaction:
The following are examples of how a solute can be oxidation reaction:
Oxygen atom addition
- Hydrogen atom removal
- Electron donation or loss
- An overall enhance in the substance's oxidation state
Reduction reaction:
The following are examples of how a solute can be reduction reaction:
- Hydrogen atom addition
- Oxygen atom removal
- Accepting electrons
- Reduction in the oxidation state of the analyte
Redox titration curve:
It is important to understand the shape of the redox titration curve to evaluate it. The titration curve of a complexometric titration or an acid-base titration explains how the concentration of H3O+ or Mn+ varies as titrant is added. In redox titrations, it is more suitable to monitor the potential of the titration reaction rather than the concentration of a species.
Indicators used in redox titration:
Potassium permanganate, iodine, ceric ammonium sulphate, phenanthroline blue, methylene blue, ferrous ions in dichromate solution, 1, 10 phenanthroline monohydrate, 2,2’-bipyridine, 5,6-dimethyl phenanthroline, and safrannin-T. Etc. are the commonly used redox indicators.
The endpoint of redox titrations can be determined in a variety of ways such as self indicators, external Indicators, redox indicators, and instrumental techniques, etc.
The redox indicators are indicators that exhibit a reversible change of color between oxidized and reduced forms and undergo a specified color change at a specific potential. These are indicators are weak reductants or oxidizers that have different colors in their reduced and oxidized forms.
The color changes take place within a specific redox potential transition range, which must include the redox potential at the equivalence point in the redox titration to be performed.
If using an oxidizing volumetric solution, the indicator's redox potential should be greater than the potential of the solution, and when using a reducing volumetric solution, it should be lower.
Types of redox titration:
There are different types of redox titration based on the titrant used they are bromatometry, iodometry or iodimetry, cerimetry, permanganometry, and dichrometry, etc., and based on the method they are classified as direct titration, and back titration.
Iodometric titration:
The iodometric titration is a process for determining the concentration of an oxidizing agent in a sample solution. It is a type of redox titration that uses sodium thiosulphate, as a reducing agent to titrate iodine. A starch solution is used as an indicator in an iodometric titration because it can absorb the iodine (I2) that is released.
Iodimetric titration:
When an analyte that is a reducing agent is directly titrated with a standard iodine solution, the method is called iodimetry.
Bromatometry titration:
Bromatometry is the process that involves titration by oxidation using potassium bromate. It is a type of redox titration that is used to determine the bromination of a chemical indicator.
Cerimetric titration:
Cerimetry is a method of volumetric chemical analysis that can be used for analyses of nonstoichiometric levels that either oxidize Fe2+ or reduce Fe3+. It is a type of redox titration in which the endpoint is determined by a color change in the iron (II)–1, 10-phenanthroline complex (ferroin).
Permanganometric titration:
It is a type of redox titration in which the permanganate is used to determine the amount of analyte present in unknown samples solution. Permanganometry provides the detection and quantification of different chemical species, including manganese (II), iron (II), oxalate, nitrite, and hydrogen peroxide, etc.
Dichrometry titration:
It is a qualitative analysis in chemistry it involves the use of potassium dichromate (K2Cr2O7) which is used to determine the amount of solute in the sample.
Applications of redox titration:
Redox titration is a quantitative chemical analysis method with a variety of applications, some of which are listed below.
- Redox titration applied in the pharmaceutical field
- It is used in public health and environmental analyses
- It is used in the food industry
- Applications of redox titration in different industries for research
- Applications of redox titration in chemistry
- Redox titration also used in the real-life applications
- Redox reaction used in electrochemistry
- The theory and practical taught in schools and colleges
Advantages of redox titration:
- It's usually inexpensive and requires little equipment which is generally available in the lab
- It does not need particular or expensive chemicals
- Does not require high expertise, has a simple operating procedure
- The analysis can be automated, with very precise results
- Provides quick results
Disadvantages of redox titration:
- It is a destructive technique that frequently consumes large amounts of the substance being analyzed
- It requires reactions to take place in a liquid phase
- It produces large volumes of chemical waste
Commonly asked questions on redox titration are as follows.
What are the factors affecting redox titrations?
The concentration of reactant, completeness of the reaction, temperature, and pH are the major factors that affect redox titration.
What are apparatus needed for titration?
Apparatus used to perform titration consist burette, stand, conical flask, pipette, funnel, beaker, volumetric flask, burette and wash bottle, etc., as well as some instruments such as pH meter, conductivity meter, colorimeter, Karl-Fischer titrator, and potentiometer, etc., are also used for different methods of titration.
What is the importance of the redox reaction?
A wide range of inorganic analytes can be analyzed using redox titration Oxidation-reduction reactions are extremely important not just in chemistry, biochemistry, and industrial processes, but also in geology and biology.
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