Photochemical smog is formed due to presence of :

Options

A. oxides of sulphur
B. Oxides of nitrogen
C. oxides of carbon
D. oxides of lead

Answer

To solve the question regarding the formation of photochemical smog, we will analyze the components involved in its formation step by step.

### Step-by-Step Solution:

1. **Understanding Photochemical Smog**:
Photochemical smog is a type of air pollution that is formed when sunlight reacts with pollutants in the atmosphere. It primarily occurs in urban areas with heavy traffic.

**Hint**: Remember that photochemical smog is associated with sunlight and specific pollutants.

2. **Identifying Key Pollutants**:
The main components involved in the formation of photochemical smog include nitrogen oxides (NOx) and volatile organic compounds (VOCs).

**Hint**: Focus on the types of pollutants that are prevalent in urban environments.

3. **Role of Nitrogen Oxides**:
Nitrogen oxides, particularly nitrogen dioxide (NO2), are significant contributors to photochemical smog. They react with VOCs in the presence of sunlight.

**Hint**: Consider how nitrogen oxides interact with other compounds in the atmosphere.

4. **Chemical Reactions**:
- The reaction begins with nitrogen oxides (NO) reacting with VOCs to form nitrogen dioxide (NO2).
- NO2 then absorbs sunlight, leading to the formation of nitric oxide (NO) and nascent oxygen (O).
- The nascent oxygen reacts with atmospheric oxygen (O2) to produce ozone (O3).

**Hint**: Visualize the sequence of reactions that lead to the formation of ozone.

5. **Formation of Other Compounds**:
The nitrogen dioxide can also react with VOCs to form peroxyacetyl nitrate (PAN), which is another component of photochemical smog.

**Hint**: Think about the secondary reactions that occur after the initial formation of nitrogen dioxide.

6. **Conclusion**:
Based on the reactions and components discussed, the correct answer to the question is that photochemical smog is formed due to the presence of **oxides of nitrogen**.

**Hint**: Review the options provided and eliminate those that do not participate in the formation of photochemical smog.

### Final Answer:
Photochemical smog is formed due to the presence of **oxides of nitrogen**.