In acidic medium, reaction `MnO_(4)^(-) hArr Mn^(2+)` is an example of -

Options

A. Oxidation by three electrons
B. Reduction by three electrons
C. Oxidation by five electrons
D. Reduction by five electrons

Answer

To solve the question regarding the reaction \( \text{MnO}_4^{-} \rightleftharpoons \text{Mn}^{2+} \) in acidic medium, we need to determine the nature of the reaction. Here’s the step-by-step solution:

### Step 1: Determine the oxidation state of manganese in \( \text{MnO}_4^{-} \)

1. The formula for permanganate ion is \( \text{MnO}_4^{-} \).
2. Let the oxidation state of manganese (Mn) be \( x \).
3. Each oxygen atom has an oxidation state of -2. Since there are 4 oxygen atoms, their total contribution is \( 4 \times (-2) = -8 \).
4. The overall charge of the permanganate ion is -1. Therefore, we can set up the equation:
\[ x + (-8) = -1 \]
5. Solving for \( x \):
\[ x - 8 = -1 \\ x = -1 + 8 \\ x = +7 \]
Thus, the oxidation state of manganese in \( \text{MnO}_4^{-} \) is +7.

### Step 2: Determine the oxidation state of manganese in \( \text{Mn}^{2+} \)

1. In the ion \( \text{Mn}^{2+} \), the oxidation state of manganese is simply +2.

### Step 3: Analyze the change in oxidation state

1. The oxidation state of manganese changes from +7 in \( \text{MnO}_4^{-} \) to +2 in \( \text{Mn}^{2+} \).
2. The change in oxidation state can be calculated as:
\[ +7 \rightarrow +2 \]
This indicates a decrease in oxidation state.

### Step 4: Identify the type of reaction

1. A decrease in oxidation state indicates that the species is gaining electrons.
2. Since \( \text{MnO}_4^{-} \) is being reduced to \( \text{Mn}^{2+} \), this reaction is classified as a reduction reaction.

### Conclusion

The reaction \( \text{MnO}_4^{-} \rightleftharpoons \text{Mn}^{2+} \) in acidic medium is an example of a **reduction reaction**.

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