Which one of the following compounds is a peroxide?

Options

A. `KO_(2)`
B. `BaO_(2)`
C. `MnO_(2)`
D. `NO_(2)`

Answer

To determine which of the given compounds is a peroxide, we need to analyze the oxidation states of oxygen in each compound. A peroxide is characterized by having an oxidation state of -1 for at least one of the oxygen atoms.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are:
- KO2 (Potassium superoxide)
- BaO2 (Barium peroxide)
- MnO2 (Manganese dioxide)
- NO2 (Nitrogen dioxide)

2. **Analyze KO2**:
- Potassium (K) has an oxidation state of +1.
- Let the oxidation state of oxygen be \( x \).
- The equation becomes: \( 1 + 2x = 0 \).
- Solving for \( x \):
\[ 2x = -1 \implies x = -\frac{1}{2} \]
- Since the oxidation state of oxygen is -1/2, KO2 is classified as a superoxide, not a peroxide.

3. **Analyze BaO2**:
- Barium (Ba) has an oxidation state of +2.
- Let the oxidation state of oxygen be \( x \).
- The equation becomes: \( 2x + 2 = 0 \).
- Solving for \( x \):
\[ 2x = -2 \implies x = -1 \]
- The oxidation state of oxygen is -1, which confirms that BaO2 is a peroxide.

4. **Analyze MnO2**:
- Manganese (Mn) has an oxidation state of +4.
- Let the oxidation state of oxygen be \( x \).
- The equation becomes: \( 4 + 2x = 0 \).
- Solving for \( x \):
\[ 2x = -4 \implies x = -2 \]
- The oxidation state of oxygen is -2, indicating that MnO2 is a normal oxide.

5. **Analyze NO2**:
- Nitrogen (N) has an oxidation state of +4.
- Let the oxidation state of oxygen be \( x \).
- The equation becomes: \( 4 + 2x = 0 \).
- Solving for \( x \):
\[ 2x = -4 \implies x = -2 \]
- The oxidation state of oxygen is -2, indicating that NO2 is also a normal oxide.

6. **Conclusion**:
- Among the compounds analyzed, only BaO2 has an oxidation state of -1 for oxygen, which confirms it as a peroxide. Therefore, the correct answer is **BaO2**.