Which of the following reactions is not a redox reaction?

Options

A. `H_(2)O_(2)+KOHrarrKHO_(2)+H_(2)O`
B. `Cr_(2)O_(7)^(2-)+2overset(ө)OHrarr2CrO_(4)^(2-)+H_(2)O`
C. `Ca(HCO_(3))_(3)overset(Delta)rarrCaCO_(3)+CO_(2)+H_(2)O`
D. `H_(2)O_(2)rarrH_(2)O+(1)/(2)O_(2)`

Explanation

To determine which of the following reactions is not a redox reaction, we need to analyze each reaction by identifying the oxidation states of the elements involved and checking for any changes in those oxidation states. A redox reaction involves both oxidation (increase in oxidation state) and reduction (decrease in oxidation state).

### Step-by-Step Solution:

1. **Identify the Reactions:**
- Reaction 1: \( \text{H}_2\text{O}_2 + \text{KOH} \rightarrow \text{KHO}_2 + \text{H}_2\text{O} \)
- Reaction 2: \( \text{Cr}_2\text{O}_7^{2-} + 2 \text{OH}^- \rightarrow 2 \text{CrO}_4^{2-} + \text{H}_2\text{O} \)
- Reaction 3: \( \text{Ca(HCO}_3\text{)}_2 \text{ (twice)} \rightarrow \text{CaCO}_3 + \text{CO}_2 + \text{H}_2\text{O} \)
- Reaction 4: \( \text{H}_2\text{O}_2 \rightarrow \text{H}_2\text{O} + \frac{1}{2} \text{O}_2 \)

2. **Analyze Reaction 1:**
- **Oxidation States:**
- \( \text{H}_2\text{O}_2 \): H = +1, O = -1
- \( \text{KOH} \): K = +1, O = -2, H = +1
- \( \text{KHO}_2 \): K = +1, H = +1, O = -1
- \( \text{H}_2\text{O} \): H = +1, O = -2
- **Comparison:**
- No change in oxidation states for H, K, or O.
- **Conclusion:** Not a redox reaction.

3. **Analyze Reaction 2:**
- **Oxidation States:**
- \( \text{Cr}_2\text{O}_7^{2-} \): Cr = +6, O = -2
- \( \text{OH}^- \): O = -2, H = +1
- \( \text{CrO}_4^{2-} \): Cr = +6, O = -2
- \( \text{H}_2\text{O} \): H = +1, O = -2
- **Comparison:**
- No change in oxidation states for Cr, O, or H.
- **Conclusion:** Not a redox reaction.

4. **Analyze Reaction 3:**
- **Oxidation States:**
- \( \text{Ca(HCO}_3\text{)}_2 \): Ca = +2, H = +1, C = +4, O = -2
- \( \text{CaCO}_3 \): Ca = +2, C = +4, O = -2
- \( \text{CO}_2 \): C = +4, O = -2
- \( \text{H}_2\text{O} \): H = +1, O = -2
- **Comparison:**
- No change in oxidation states for Ca, C, O, or H.
- **Conclusion:** Not a redox reaction.

5. **Analyze Reaction 4:**
- **Oxidation States:**
- \( \text{H}_2\text{O}_2 \): H = +1, O = -1
- \( \text{H}_2\text{O} \): H = +1, O = -2
- \( \text{O}_2 \): O = 0
- **Comparison:**
- O changes from -1 in \( \text{H}_2\text{O}_2 \) to -2 in \( \text{H}_2\text{O} \) (reduction) and from -1 to 0 in \( \text{O}_2 \) (oxidation).
- **Conclusion:** This is a redox reaction.

### Final Conclusion:
The reactions that are **not** redox reactions are:
- Reaction 1: \( \text{H}_2\text{O}_2 + \text{KOH} \rightarrow \text{KHO}_2 + \text{H}_2\text{O} \)
- Reaction 2: \( \text{Cr}_2\text{O}_7^{2-} + 2 \text{OH}^- \rightarrow 2 \text{CrO}_4^{2-} + \text{H}_2\text{O} \)
- Reaction 3: \( \text{Ca(HCO}_3\text{)}_2 \text{ (twice)} \rightarrow \text{CaCO}_3 + \text{CO}_2 + \text{H}_2\text{O} \)