Which of the following statements about the following reaction is`//`are not correct?
`Cr_(2)O_(7)^(2-)+3H_(2)O_(2)+8H^(o+)to2Cr^(3+)+7H_(2)O+3O_(2)`

Options

A. `H_(2)O_(2)` is oxidised to `O_(2)`
B. `H_(2)O_(2)` is reduced to `H_(2)O`
C. The oxidation number of chromium atom changes by 3.
D. Hydrogen ions are oxidised to `H_(2)O`

Explanation

To determine which statements about the reaction

\[ \text{Cr}_2\text{O}_7^{2-} + 3\text{H}_2\text{O}_2 + 8\text{H}^+ \rightarrow 2\text{Cr}^{3+} + 7\text{H}_2\text{O} + 3\text{O}_2 \]

are not correct, we will analyze the oxidation states of the elements involved and the roles of the reactants.

### Step 1: Identify the oxidation states
- In \(\text{Cr}_2\text{O}_7^{2-}\), chromium (Cr) has an oxidation state of +6.
- In \(\text{H}_2\text{O}_2\), hydrogen (H) has an oxidation state of +1 and oxygen (O) has an oxidation state of -1.
- In the products, \(\text{Cr}^{3+}\) has an oxidation state of +3, and in water (\(\text{H}_2\text{O}\)), hydrogen remains +1 and oxygen is -2.

### Step 2: Determine the changes in oxidation states
- Chromium is reduced from +6 in \(\text{Cr}_2\text{O}_7^{2-}\) to +3 in \(\text{Cr}^{3+}\).
- Hydrogen peroxide (\(\text{H}_2\text{O}_2\)) is oxidized to oxygen (\(\text{O}_2\)), where the oxidation state of oxygen changes from -1 in \(\text{H}_2\text{O}_2\) to 0 in \(\text{O}_2\).

### Step 3: Analyze the statements
1. **H2O2 is oxidized to O2**: This statement is correct because \(\text{H}_2\text{O}_2\) loses electrons (is oxidized) to form \(\text{O}_2\).
2. **H2O2 is reduced to water**: This statement is incorrect because \(\text{H}_2\text{O}_2\) is oxidized, not reduced.
3. **The oxidation number of chromium atom changes by three**: This statement is correct as the oxidation state changes from +6 to +3, which is a change of 3.
4. **Hydrogen ions are oxidized**: This statement is incorrect because the oxidation state of hydrogen remains +1 in both reactants and products.

### Conclusion
The statements that are not correct are:
- H2O2 is reduced to water.
- Hydrogen ions are oxidized.