KMnO4 is a potent oxidizer, and as a result, oxalic acid is oxidized to carbon dioxide (CO2). Therefore, its deep purple color disappears and Mn²⁺ ions are formed. These give a very light pink color to the aqueous solution, while bubbling can be seen.
In the redox titration of potassium permanganate (KMnO4) against the standard solution of oxalic acid (C2H2O4), potassium permanganate is a strong oxidizing agent and becomes even more potent when sulfuric acid (H2SO4), is present.
The following equation represents the oxidizing ability of KMnO4 in an acidic medium.
MnO4– + 8H+ + 5e– → Mn2+ + 4H2O
When permanganate solution is introduced to a solution containing a reducing agent, the permanganate solution is decolorized because the solution containing MnO4- ions is purple while the solution containing Mn2+ ions is colorless. At the moment when KMnO4 is present in excess, the solution turns purple. Consequently, KMnO4 acts as a self-indicator in acidic solutions.
Frequently Asked Question (FAQ):
Explain in short why adding oxalic acid to KMnO4's solution in an acidic medium causes the color to disappear.
Potassium permanganate oxidizes oxalic acid to CO2 and itself turns into Mn2+ ions which are colorless.
What color change occurs at the endpoint of the permanganate oxalate reaction?
As permanganate is added to the oxalate solution, it turns purple and then the permanganate is consumed, and the purple color disappears. As more permanganate is added and eventually all oxalates are oxidized, and the endpoint is indicated by the appearance of a faint purple color, due to the presence of excess permanganate.
Why in the titration of oxalic acid with KMnO4 pink colour disappears slowly at the beginning but rapidly afterwards?
Because of the formation of Mn2+ ions which act as auto-catalysts for the reaction, the pink colour disappears slowly at the beginning but rapidly afterwards.
People also ask:
- Why does KMnO4 disappear when oxalic acid?
- Does oxalic acid decolorize potassium permanganate?
- When KMnO4 is reduced with oxalic acid the Decolourisation?
- Why the purple colour of permanganate disappears by adding it to the aqueous solution of oxalic acid?
- Why in the titration of oxalic acid with KMnO4 pink colour disappears slowly at the beginning but rapidly afterwards?
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