60. In acidic solution, permanganate ion is reduced by ferrous ion. The number of electrons involved in the reduction of permanganate ion is______
Reduction of Permanganate Ion by Ferrous Ion in Acidic Medium – Complete Redox Reaction Explained
In this question, the permanganate ion reacts with ferrous ion (Fe2+) under acidic conditions. The objective is to determine the number of electrons involved in the reduction of a single permanganate ion.
Understanding the Reaction
In acidic medium, the permanganate ion acts as a powerful oxidizing agent. It accepts electrons from ferrous ions, causing the ferrous ions to be oxidized into ferric ions. At the same time, the manganese atom in permanganate is reduced from a higher oxidation state to a lower oxidation state.
The oxidation state of manganese in MnO4− is +7.
After reduction in acidic medium, manganese forms the Mn2+ ion, where the oxidation state of manganese becomes +2.
Thus, the oxidation number changes from
+7 → +2
This represents a decrease of
5 oxidation units
Therefore, one permanganate ion gains 5 electrons.
Reduction Half-Reaction
The balanced reduction half-reaction in acidic medium is
MnO4− + 8H+ + 5e− → Mn2+ + 4H2O
This equation clearly shows that each permanganate ion accepts exactly five electrons during reduction.
Oxidation Half-Reaction
Ferrous ion undergoes oxidation according to the reaction
Fe2+ → Fe3+ + e−
Each ferrous ion loses only one electron.
Therefore, five ferrous ions are required to provide the five electrons needed to reduce one permanganate ion.
Overall Balanced Redox Reaction
The complete balanced equation is
MnO4− + 5Fe2+ + 8H+ → Mn2+ + 5Fe3+ + 4H2O
This balanced reaction confirms that one permanganate ion accepts five electrons while five ferrous ions each donate one electron.
Why Permanganate is a Strong Oxidizing Agent
Permanganate ion contains manganese in its highest common oxidation state of +7. Because this oxidation state is highly unstable, manganese readily gains electrons to achieve the much more stable +2 oxidation state in acidic medium. This strong tendency to accept electrons makes potassium permanganate one of the most powerful oxidizing agents used in analytical chemistry, volumetric analysis, and industrial oxidation reactions.
Final Answer
Number of electrons involved = 5
Correct Answer: 5
