Photochemical smog is composed mainly of ,

Options

A. `O_(3) "PAN and " O_(2)`
B. `O_3,SO_(2), NO_(2)`
C. `O_(3),NO_(2),PAN`
D. `SO_(2),CO_(2),O_(3)`

Answer

To answer the question regarding the composition of photochemical smog, we can break down the information systematically:

### Step-by-Step Solution:

1. **Definition of Photochemical Smog**:
Photochemical smog is a type of air pollution that is characterized by a brownish-grey haze. It typically occurs in urban areas during sunny, dry weather conditions.

2. **Formation Process**:
Photochemical smog is formed through the action of solar ultraviolet (UV) radiation on pollutants in the atmosphere. This process primarily involves hydrocarbons and nitrogen oxides (NOx).

3. **Key Components**:
The main components of photochemical smog include:
- **Ozone (O3)**: Formed when UV light reacts with nitrogen oxides and volatile organic compounds (VOCs).
- **Nitrogen Dioxide (NO2)**: A product of combustion processes that contributes to the formation of ozone.
- **Peroxyacetyl Nitrate (PAN)**: A secondary pollutant formed from the reaction of nitrogen oxides and organic compounds.

4. **Chemical Reactions**:
- Nitrogen dioxide (NO2) reacts with sunlight to produce nitric oxide (NO) and nascent oxygen (O).
- The nascent oxygen then reacts with molecular oxygen (O2) to form ozone (O3).
- Ozone can further react with hydrocarbons to form aldehydes and other organic compounds.
- The reaction of these compounds can lead to the formation of PAN.

5. **Conclusion**:
The main components of photochemical smog are ozone (O3), nitrogen dioxide (NO2), and peroxyacetyl nitrate (PAN). Therefore, the correct answer to the question is that photochemical smog is composed mainly of these substances.

### Final Answer:
Photochemical smog is composed mainly of ozone (O3), nitrogen dioxide (NO2), and peroxyacetyl nitrate (PAN).

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