Titration (also known as titrimetry and volumetric analysis) is the most common quantitative and volumetric lab technique for determining the unknown concentration of an analyte by comparing it with the known concentration of a solution in the presence of an indicator.
Depending on the goals and process, there are different types of titrations, such as acid-base titrations, redox titrations, complexometric titrations, and precipitation titrations.
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What is redox titration?
Redox titration is a method used in the laboratory to find out the concentration of the analyte by carrying out a redox reaction between the analyte and the titrant.
This titrimetric method is mostly based on the change in oxidation number or the transfer of electrons between the reactants. This means that these reactions are mostly based on oxidation-reduction reactions.
In the oxidation-reduction titration, a reducing substance is titrated with a standard solution of an oxidizing agent (For example - ceric ammonium sulphate (NH4)4Ce (SO4)4), or an oxidizing substance is titrated with the standard solution of the reducing agent(e.g., titanous chloride- TiCl3).
For redox titration evaluation, it is significant to obtain the shape of the titration curve that corresponds. In redox titration, it is much easier to monitor the concentration of the reaction potential rather than the concentration of the reacting species.
What is the principle of redox titration?
The principle behind the oxidation-reduction (Redox) titration is that during the oxidation process, electrons are lost, whereas, during the reduction process, electrons are gained.
Oxidant + ne ↔ Reductant
How will we be able to detect the oxidation of a substance?
The substance has experienced oxidation if even one of the scenarios listed below occurs.
If hydrogen is removed from the given substance, if the substance loses electrons, if the oxidation state exhibited by the substance increases, and if oxygen is added to the substance.
How will we be able to detect the reduction of a substance?
If even one of the possibilities listed below is true, we can conclude that the substance has undergone reduction.
If hydrogen is added to the substance, if the oxidation state exhibited by the substance decreases, if the substance gains electrons and if oxygen is removed from the given substance.
So, you can conclude that there is a transfer of electrons between the analyte and the titrant during redox titrations.
What is the example of redox titration?
An example of redox titration is when an iodine (I2 )solution is treated with a reducing agent such as thiosulfate (Na2S2O3 ) to produce iodide using a starch indicator to detect the endpoint, also referred to as iodometric titration. Another example is the titration of potassium permanganate with oxalic acid.
What are the types of redox titration?
Depending on the titrant used, there are several forms of redox titrations, such as iodometry which uses iodine, dichrometry which uses potassium dichromate, cerimetry which uses cerium(IV) salts, permanganometry which uses potassium permanganate, and bromatometry which uses a bromine (Br2) titrant, etc., and depending on the method, direct titrations, and back titration.
Frequently Asked Question (FAQ):
What is redox titration used for?
Redox titrations are used to determine the concentration of an unknown substance in a solution. The equivalence point is found when the titrant and analyte have reacted stoichiometrically by transferring electrons.
Which indicator is used in redox titration?
A redox indicator is an indicator that changes color change at a specific electrode potential. There are two common classes of redox indicators used in the redox reaction: pH independent (e.g. Diphenylamine, Nitrophenanthroline) and pH dependent (e.g. Methylene blue, Indigo carmine)
What is the role of phosphoric acid in redox titration?
Phosphoric acid is added to reduce the electrode potential for the Fe3+ → Fe2+ by stabilizing the ferric ion. This ensures that the ferric product, Fe3+, remains in its colorless form.
Which is the factor that affects redox titration?
pH is the only factor that influences redox titration. Potassium permanganate (KMnO4) is a good example because it has the maximum oxidizing effect in an acidic condition and the lowest in an alkaline medium.
What are self-indicators?
A self-indicator is a chemical molecule that, in addition to self-participating in the reaction, can also serve as an indicator when the analyte and titrant have finished reacting (Endpoint/equivalence point). An example of a self-indicator is KMnO4.
What is a back titration in chemistry?
A back titration is a technique for estimating the concentration of an analyte by reacting it with an excess of a known reagent. The remaining excess reagent is then titrated with another, second reagent.
Key terms used in redox titrations:
- Redox titration/oxidation-reduction titration:
A kind of titration in which the analyte and titrant undergo a redox reaction
- Burette:
A graduated glass tube having a tap at one end is used for titration to administer known volumes of liquid.
- Analyte:
A substance whose quantity/concentration is to be determined.
- Titrant:
A solution with a known concentration is filled in the burette that is added to another solution to find out the concentration of a second chemical species.
- Oxidation:
Oxidation is a chemical process that happens when an atom, molecule, or ion loses one or more electrons. Oxidation increases the oxidation state of a chemical species.
- Reduction:
A chemical reaction between two substances in which one of the atoms in the reaction gains an electron.
- Reducing agent:
A reactant gets oxidized to produce electrons in the reaction.
- Oxidizing agent:
A reactant that undergoes a reduction reaction to gain electrons.
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References:
- GH Jeffery, J Bassett, J Mendham, RD Denney, Vogel's Textbook of Quantitative Chemical Analysis, 5th ed, 1989, Wiley, NY.
- Wikipedia contributors. "Redox titration." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 4 Feb. 2022.
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