Which one of the following compounds is a superoxide?

Options

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

Answer

To determine which compound is a superoxide, we need to understand the definition of a superoxide and analyze the oxidation states of oxygen in the given compounds.

### Step-by-Step Solution:

1. **Definition of Superoxide**:
A superoxide is a compound that contains the superoxide ion (O2^−) where the oxidation state of each oxygen atom in the ion is -1/2.

2. **Analyzing the Options**:
We will evaluate each option to see if it contains the superoxide ion.

- **Option 1: KO2 (Potassium Superoxide)**:
- Potassium (K) is in Group 1 and has a +1 oxidation state.
- The compound can be represented as K^+ and O2^2−.
- The two oxygen atoms in O2^2− have an average oxidation state of -1/2 (since 2 oxygen atoms share a -1 charge).
- Therefore, KO2 is a superoxide.

- **Option 2: BaO2 (Barium Peroxide)**:
- Barium (Ba) is in Group 2 and has a +2 oxidation state.
- In BaO2, the two oxygen atoms share a -2 charge, leading to an average oxidation state of -1 for each oxygen.
- This indicates that BaO2 is a peroxide, not a superoxide.

- **Option 3: MnO2 (Manganese Dioxide)**:
- Manganese (Mn) typically has a +4 oxidation state in MnO2.
- The two oxygen atoms each have a -2 oxidation state.
- Thus, MnO2 is a normal oxide, not a superoxide.

- **Option 4: NO2 (Nitrogen Dioxide)**:
- Nitrogen (N) in NO2 has a +4 oxidation state.
- The two oxygen atoms each have a -2 oxidation state.
- Therefore, NO2 is also a normal oxide, not a superoxide.

3. **Conclusion**:
After analyzing all the options, we find that the only compound that qualifies as a superoxide is **KO2**.

### Final Answer:
The compound that is a superoxide is **KO2**.