Which of the following reactions does not involve either oxidation or reduction ?

Options

A. `VO^(2+)rarrV_(2)O_(3)`
B. `NararrNa^(o+)`
C. `CrO_(4)^(2-)rarrCr_(2)O_(7)^(2-)`
D. `Zn^(2+)rarrZn`

Explanation

To determine which of the following reactions does not involve either oxidation or reduction, we need to analyze the oxidation states of the elements involved in each reaction. Here’s a step-by-step solution:

### Step 1: Analyze the first reaction
**Reaction:** VO2⁺ → V2O3
- **Oxidation State of V in VO2⁺:** +4
- **Oxidation State of V in V2O3:** +3
- **Change:** The oxidation state of V decreases from +4 to +3, indicating a reduction.
**Conclusion:** This reaction involves reduction.

### Step 2: Analyze the second reaction
**Reaction:** Na → Na⁺
- **Oxidation State of Na:** 0
- **Oxidation State of Na⁺:** +1
- **Change:** The oxidation state of Na increases from 0 to +1, indicating oxidation.
**Conclusion:** This reaction involves oxidation.

### Step 3: Analyze the third reaction
**Reaction:** CrO4²⁻ → Cr2O7²⁻
- **Oxidation State of Cr in CrO4²⁻:** +6
- **Oxidation State of Cr in Cr2O7²⁻:** +6
- **Change:** The oxidation state of Cr remains the same at +6 in both compounds.
**Conclusion:** This reaction does not involve any change in oxidation state, hence it does not involve oxidation or reduction.

### Step 4: Analyze the fourth reaction
**Reaction:** Zn²⁺ → Zn
- **Oxidation State of Zn²⁺:** +2
- **Oxidation State of Zn:** 0
- **Change:** The oxidation state of Zn decreases from +2 to 0, indicating reduction.
**Conclusion:** This reaction involves reduction.

### Final Conclusion
Among the reactions analyzed, only the third reaction (CrO4²⁻ → Cr2O7²⁻) does not involve either oxidation or reduction. Therefore, the correct answer is:

**Correct Option:** C (CrO4²⁻ → Cr2O7²⁻)

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