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The titration of potassium permanganate (KMnO4)against oxalic acid is used to demonstrate redox titration in this experiment (C2H2O4). As long as the endpoint is in close proximity to the indicator in oxidation-reduction (redox) titrations, the action of the indicator is analogous to that of other types of visual colour titrations.
Theory
Sulfuric acid, combined with potassium permanganate, produces an even more potent oxidising agent. Potassium permanganate is a powerful oxidising agent. According to the following equation, the oxidising ability of KMnO4 in an acidic medium is represented.
MnO4- + 8H+ + 5e- -> Mn2++ 4H2O
Due to the presence of MnO4- ions in purple solutions, whereas Mn2+ ions are present in colourless solutions, when a permanganate solution is added to a reducing agent solution, the solution becomes decolored as a result. Because of an excess of potassium permanganate in the solution, the colour of the solution changes to purple when there is an excess of the compound. This property allows KMnO4 to function as a self-indicator for acidic solutions.
Potassium permanganate has a higher standardised value than pure oxalic acid, which is a good thing. Redox reactions are responsible for this phenomenon. Oxalic acid is converted to carbon dioxide by the presence of KMnO4, which is then converted to MnSO4 by the presence of oxygen. Whenever oxalic acid and potassium permanganate come into contact, the following reaction occurs:
Described below is a description of the chemical reaction that takes place at room temperature.
Reduction Half reaction:- 2KMnO4 + 3H2SO4 → K2SO4 + 2MnSO4 + 3H2O + 5[O]
Oxidation Half reaction:- 5(COOH)2 + 5[O] → 5H2O + 10CO2↑
The overall reaction that occurs throughout the process is
In general, reduction reactions are as follows:
Overall reaction:- 2KMnO4 + 3H2SO4 + 5(COOH)2 → K2SO4 + 2MnSO4 + 8H2O + 10CO2↑
The ionic equation involved in the process is given below.
Reduction Half reaction:- [MnO4-+8H++5e- → Mn2++4H2O]×2
Oxidation Half reaction:- [c2O42-→2CO2+2e-]×5
Overall Ionic reaction:- 2MnO4-+16H++5C2O42-→2Mn2++10CO2+8H2O
It is not possible to perform this titration in the presence of acids such as nitric acid or hydrochloric acid because the titration is an oxidising agent in and of itself. Chlorine is formed as a result of the chemical reaction between hydrochloric acid and KMnO4 solution. Chlorine is also an oxidising agent as a result of the chemical reaction.
Precautions:
- Preparing for the experiment begins with thorough cleaning of all of the apparatus with distilled water, followed by filling them with the solution that will be employed.
- Thoroughly rinse the pipette and burette before using them. 3.
Because it is dark in colour, the upper meniscus of potassium permanganate should always be read when preparing a solution.
- Dilute sulfuric acid should be used for the acidification of the potassium permanganate.
After it reaches the destination, take accurate readings rather than relying on an average of the previous measurements.
- Use an antiparallex card or an autoparallex card to ensure that the burette readings are accurate while taking them.
KMnO4is particularly dangerous to use with a rubber cork burette because it is susceptible to attack by the compound.
To complete this eighth rule, only two decimal places should be used to calculate the strength of the unknown solution.
Mohr’s salt titration with KMnO4
Introduction
The inorganic compound ammonium ferrous (ll) sulphate (NH₄)₂Fe(SO₄)₂(H₂O)₆, also known as Mohr’s salt, is an example of an inorganic compound. It is a crystalline double slat of ammonium sulphate and ferrous sulphate with a green colour and a crystalline structure that is used in the production of fertiliser.
Precautions
- Before using the burette, pipette, and flask, make sure they are thoroughly cleaned.
- Before beginning the experiment, thoroughly clean all of the equipment.
The acid should be diluted to an appropriate concentration before carrying out this experiment, as shown in step three.
- Do not leave the potassium permanganate solution in the burette for an indefinite period of time.
Make sure to thoroughly shake the conical flask after each addition of potassium permanganate solution to ensure that the solution is evenly distributed.
- Once the solution has achieved a permanent pink colour and does not disappear when shaken, it is no longer necessary to add potassium permanganate solution to the solution.
To ensure that the experiment’s results are accurate, always take at least three sets of readings for the experiment.
Conclusion
Titration with a standard solution of 0.1M oxalic acid was performed in order to determine the strength of potassium permanganate in solution.
A potassium permanganate solution is tested against a standard ferrous ammonium sulphate (Mohr’s salt) solution to determine its strength.
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