MediumChemistryHigh School (11–12)Redox Reactions › Balancing Redox Equations and Redox TitrationsNumericalA-LevelAPIBJEE Main
In acid, permanganate oxidises oxalate ions to carbon dioxide: MnO₄⁻ + C₂O₄²⁻ → Mn²⁺ + CO₂…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
In acid, permanganate oxidises oxalate ions to carbon dioxide: . Find the electrons gained by one permanganate ion and lost by one oxalate ion. Then find how many oxalate ions react with 2 permanganate ions.
Need a reminder? The key ideaShow
The total rise in oxidation number equals the total fall: electrons lost equal electrons gained. Match the changes first. Then balance the atoms that did not change, charge, hydrogen and oxygen.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Manganese. From to : each permanganate ion gains 5 electrons.
Step 2. Carbon. In the oxalate ion, , so each carbon is . In carbon dioxide it is . Each carbon rises by 1, and there are two carbon atoms in each ion. So each oxalate ion loses 2 electrons.
Step 3. Match. Two permanganate ions gain electrons. Each oxalate ion loses 2, so oxalate ions are needed.
Answer: 5 electrons gained, 2 electrons lost, and 5 oxalate ions for 2 permanganate ions. The ratio is .
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