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

Options

A. `VO^(2+) rarr V_(2) O_(3)`
B. `Na rarr Na^(+)`
C. `Zn^(+2) rarr Zn`
D. `CrO_(4)^(-2) rarr Cr_(2) O_(7)^(-2)`

Answer

To determine which of the given reactions does not involve either oxidation or reduction, we need to analyze the changes in oxidation states of the elements involved in each reaction.

### Step-by-Step Solution:

1. **Identify the Reactions**:
We need to examine the provided reactions and identify the oxidation states of the elements involved.

2. **Analyze the First Reaction (VO2⁺ to V2O3)**:
- For VO2⁺:
- Oxygen (O) has an oxidation state of -2.
- Let the oxidation state of Vanadium (V) be x.
- The equation becomes: x + 2(-2) = +2 (charge of VO2⁺).
- Solving gives x = +4.
- For V2O3:
- Let the oxidation state of V be y.
- The equation becomes: 2y + 3(-2) = 0.
- Solving gives y = +3.
- Change in oxidation state: +4 to +3 (reduction).

3. **Analyze the Second Reaction (Sodium from 0 to +1)**:
- Sodium (Na) is going from an oxidation state of 0 to +1.
- This indicates a loss of electrons (oxidation).

4. **Analyze the Third Reaction (Zinc from +2 to 0)**:
- Zinc (Zn) is going from +2 to 0.
- This indicates a gain of electrons (reduction).

5. **Analyze the Fourth Reaction (CrO4²⁻ to Cr2O7²⁻)**:
- For CrO4²⁻:
- Let the oxidation state of Chromium (Cr) be x.
- The equation becomes: x + 4(-2) = -2.
- Solving gives x = +6.
- For Cr2O7²⁻:
- The equation becomes: 2x + 7(-2) = -2.
- Solving gives x = +6.
- Change in oxidation state: +6 to +6 (no change).

6. **Conclusion**:
The only reaction that does not involve a change in oxidation state (and therefore does not involve oxidation or reduction) is the conversion of CrO4²⁻ to Cr2O7²⁻.

### Final Answer:
The reaction that does not involve either oxidation or reduction is the conversion of CrO4²⁻ to Cr2O7²⁻.