Which of the following is not correct ?

Options

A. `H_2O_2` oxidizes Fe (II) to Fe (III)
B. `H_2O_2` is a weak base
C. `H_2O_2` can be obtained by the electrolysis of dil . `H_2SO_4` .
D. `H_2O_2` reduces Mn (VII) to Mn (II)

Answer

To solve the question, we need to evaluate each of the given statements and determine which one is not correct.

### Step-by-Step Solution:

1. **Evaluate Option A: H2O2 oxidizes Fe2+ to Fe3+.**
- H2O2 (hydrogen peroxide) acts as an oxidizing agent. In this reaction, Fe2+ (ferrous ion) is oxidized to Fe3+ (ferric ion).
- The balanced reaction in acidic medium is:
\[ 2Fe^{2+} + H_2O_2 + 2H^+ \rightarrow 2Fe^{3+} + 2H_2O \]
- Since Fe2+ is converted to Fe3+, this statement is **correct**.

2. **Evaluate Option B: H2O2 is a weak base.**
- H2O2 is known to exhibit acidic properties rather than basic. It can donate protons (H+) in solution, which is characteristic of acids.
- The pH of H2O2 solutions typically ranges from 3 to 6, indicating it behaves as a weak acid.
- Therefore, this statement is **not correct**.

3. **Evaluate Option C: H2O2 can be obtained by the electrolysis of dilute H2SO4.**
- Hydrogen peroxide can indeed be produced by the electrolysis of dilute sulfuric acid (H2SO4).
- The reaction involves the formation of peroxydisulfate, which can then hydrolyze to produce H2O2:
\[ 2HSO_4^- \rightarrow H_2S_2O_8 + 2e^- \]
\[ H_2S_2O_8 + 2H_2O \rightarrow 2H_2O_2 + 2H_2SO_4 \]
- This statement is **correct**.

4. **Evaluate Option D: H2O2 reduces MnO4- (Mn7+) to Mn2+.**
- In acidic medium, H2O2 can reduce permanganate ions (MnO4-) from +7 oxidation state to +2.
- The balanced reaction is:
\[ 2MnO_4^- + 5H_2O_2 + 6H^+ \rightarrow 2Mn^{2+} + 8H_2O + 5O_2 \]
- This statement is also **correct**.

### Conclusion:
Based on the evaluations, the statement that is **not correct** is:
- **Option B: H2O2 is a weak base.**