Which of the following reaction(s) is/are happen during the formation of `O_3` layer in stratosphere?

Options

A. `O_2(g)overset (UV)rarr O(g)+O(g)`
B. `O(g)+O_2(g) overset(UV) rarr O_3(g)`
C. `O_3 overset(UV) rarr O_2(g)+O(g)`
D. All of the above

Answer

To determine which reactions occur during the formation of the ozone (O₃) layer in the stratosphere, we can analyze the processes involved step by step.

### Step 1: Photodissociation of Oxygen
- **Reaction**: \( \text{O}_2 \xrightarrow{UV} 2\text{O} \)
- **Explanation**: Ultraviolet (UV) radiation from the sun breaks down molecular oxygen (O₂) into two oxygen atoms (O). This process is known as photodissociation.

### Step 2: Formation of Ozone
- **Reaction**: \( \text{O} + \text{O}_2 \xrightarrow{UV} \text{O}_3 \)
- **Explanation**: The free oxygen atoms (O) produced in the first step can react with molecular oxygen (O₂) to form ozone (O₃) in the presence of UV radiation.

### Step 3: Decomposition of Ozone
- **Reaction**: \( \text{O}_3 \xrightarrow{UV} \text{O}_2 + \text{O} \)
- **Explanation**: Ozone (O₃) can also absorb UV radiation, which causes it to break down into molecular oxygen (O₂) and a free oxygen atom (O).

### Conclusion
- All three reactions described above are integral to the formation and maintenance of the ozone layer in the stratosphere. Therefore, the correct answer is that all of the reactions happen during the formation of the ozone layer.

### Final Answer
- The correct option is **All of the above**.

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