Which of the following is/are examples of unimolecular reactions?

Options

A. `O_(3) rarr O_(2)+O`
B.
C. `NO+O_(3) rarr NO_(2)+O_(2)`
D. `O+NO+N_(2) rarr NO_(2)+N_(2)`

Explanation

To determine which of the given reactions are examples of unimolecular reactions, we need to understand the concept of molecularity. Unimolecular reactions are characterized by having only one reactant species involved in the rate-determining step of the reaction. Here’s a step-by-step solution:

### Step 1: Understand Unimolecular Reactions
- **Definition**: Unimolecular reactions involve a single reactant molecule that undergoes a transformation. The molecularity of such reactions is 1.

### Step 2: Analyze Each Reaction
- **Reaction A**: Check the number of reactant species.
- There is only one ozone molecule involved.
- **Conclusion**: This is a unimolecular reaction (molecularity = 1).

- **Reaction B**: Check the number of reactant species.
- There is only one cyclopropane molecule involved.
- **Conclusion**: This is also a unimolecular reaction (molecularity = 1).

- **Reaction C**: Check the number of reactant species.
- There are two species: nitrogen monoxide (NO) and ozone (O3).
- **Conclusion**: This is not a unimolecular reaction (molecularity = 2).

- **Reaction D**: Check the number of reactant species.
- There are three species reacting.
- **Conclusion**: This is not a unimolecular reaction (molecularity = 3).

### Step 3: Identify Unimolecular Reactions
- From the analysis:
- **Unimolecular Reactions**: Reaction A and Reaction B.
- **Non-Unimolecular Reactions**: Reaction C and Reaction D.

### Final Answer
The reactions that are examples of unimolecular reactions are **A and B**.

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