Which of the following is not a redox reaction

Options

A. `2 Rb+2H_(2)O rarr 2RbOH+H_(2)`
B. `2CuI_(2) rarr 2CuI+I_(2)`
C. `2H_(2)O_(2) rarr 2H_(2)O+O_(2)`
D. `4 KCN+Fe(CN)_(2) rarr K_(4) [Fe(CN)_(6)]`

Explanation

To determine which of the following reactions is not a redox reaction, we need to analyze the oxidation states of the elements involved in each reaction. A redox reaction involves both oxidation (loss of electrons) and reduction (gain of electrons). Let's evaluate each option step by step.

### Step-by-Step Solution:

1. **Option 1: RB2H2O → RBOH + H2**
- In RB2H2O, the oxidation state of RB is 0.
- In RBOH, the oxidation state of RB is -1.
- Water (H2O) has H in +1 and O in -2. In H2, H is 0.
- Here, RB is reduced from 0 to -1 (gain of electrons), and H2O is oxidized to H2 (loss of electrons).
- **Conclusion:** This is a redox reaction.

2. **Option 2: CuI2 → CuI + I2**
- In CuI2, the oxidation state of Cu is +2 and I is -1.
- In CuI, the oxidation state of Cu is +1 and I remains -1.
- Here, Cu is reduced from +2 to +1, and I is oxidized from -1 to 0 (as I2).
- **Conclusion:** This is also a redox reaction.

3. **Option 3: H2O2 → H2O + O2**
- In H2O2, the oxidation state of O is -1.
- In H2O, the oxidation state of O is -2, and in O2, the oxidation state of O is 0.
- Here, O in H2O2 is reduced from -1 to -2 and oxidized from -1 to 0.
- **Conclusion:** This is a redox reaction as well.

4. **Option 4: 4KCN + Fe(CN)2 → K4[Fe(CN)6]**
- In KCN, K is +1 and CN is -1.
- In Fe(CN)2, Fe is +2 and CN is -1.
- In K4[Fe(CN)6], K is +1, Fe is +2, and CN is -1.
- The oxidation states of all elements remain the same before and after the reaction.
- **Conclusion:** This is not a redox reaction as there is no change in oxidation states.

### Final Answer:
The reaction that is not a redox reaction is **Option 4: 4KCN + Fe(CN)2 → K4[Fe(CN)6]**.