Incorrect statement is

Options

A. In acidic medium `MnO_(4)^(-)` disproportionates to `MnO_(2)` and `MnO_(4)^(2-)`
B. `KMnO_(4)` spot can be bleached by `H_(2)O_(2)`
C. Alkaline `KMnO_(4)` can be used to test unsaturation is
D. Eq. wt. of `KMnO_(4)` in acidic medium is `(M)/(5)`

Answer

To determine the incorrect statement from the provided options, we will analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** In acetic medium, MnO4- disproportionates to MnO2 and MnO4-.

- **Disproportionation Reaction:** A disproportionation reaction is a type of redox reaction where an element in one oxidation state is simultaneously oxidized and reduced to form two different products, one with a higher oxidation state and one with a lower oxidation state.
- **Oxidation State of Manganese in MnO4-:**
- The oxidation state of Mn in MnO4- can be calculated as follows:
- Let the oxidation state of Mn be \( x \).
- The equation will be: \( x + 4(-2) = -1 \) (since there are 4 oxygen atoms each with an oxidation state of -2).
- This simplifies to \( x - 8 = -1 \) or \( x = +7 \).
- **Conclusion for Statement 1:** Since MnO4- is already in its highest oxidation state (+7), it cannot undergo disproportionation to a higher oxidation state. Therefore, this statement is **incorrect**.

### Step 2: Analyze the second statement
**Statement:** KMnO4 spot can be bleached by H2O2.

- **Reaction:** When KMnO4 (which is purple) reacts with H2O2, it gets reduced, and H2O2 gets oxidized.
- **Products:** The reaction produces MnO2 (which is brown), oxygen, KOH, and water.
- **Conclusion for Statement 2:** This statement is **correct** as KMnO4 can indeed be bleached by H2O2.

### Step 3: Analyze the third statement
**Statement:** Alkaline KMnO4 can be used to test for unsaturation.

- **Baeyer's Reagent:** Alkaline KMnO4 is known as Baeyer's reagent and is used to identify unsaturation in organic compounds (alkenes and alkynes).
- **Reaction:** When it reacts with unsaturated compounds, the purple color of KMnO4 changes to brown due to the formation of MnO2.
- **Conclusion for Statement 3:** This statement is **correct** as alkaline KMnO4 is indeed used to test for unsaturation.

### Step 4: Analyze the fourth statement
**Statement:** The equivalent weight of KMnO4 in acidic medium is m/5.

- **Change in Oxidation State:** In acidic medium, KMnO4 (Mn in +7 oxidation state) is reduced to Mn2+ (Mn in +2 oxidation state). The change in oxidation state is 5 (from +7 to +2).
- **Equivalent Weight Calculation:**
- Equivalent weight = Molecular weight / n-factor.
- Here, n-factor = change in oxidation state = 5.
- Therefore, the equivalent weight of KMnO4 in acidic medium is indeed m/5.
- **Conclusion for Statement 4:** This statement is also **correct**.

### Final Conclusion
After analyzing all statements, the incorrect statement is the **first statement**: "In acetic medium, MnO4- disproportionates to MnO2 and MnO4-."

---