Photochemical smog includes the reduction of

Options

A. `SO_(2)`
B. NO
C. `Cl_(2)`
D. `NO_(2)`

Answer

**Step-by-Step Solution:**

1. **Understanding Photochemical Smog**: Photochemical smog is a type of air pollution that occurs when sunlight reacts with pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs). This reaction typically occurs in urban areas with heavy traffic.

2. **Role of Ultraviolet Light**: The process is initiated by ultraviolet (UV) light from the sun. This light causes chemical reactions between the pollutants present in the atmosphere.

3. **Chemical Reactions Involved**: One of the primary reactions involves nitrogen dioxide (NO2). When NO2 is exposed to UV light, it undergoes a process called photolysis, which means it breaks down into nitrogen monoxide (NO) and a free oxygen atom (O).

- **Reaction**:
\[ \text{NO}_2 \xrightarrow{\text{UV light}} \text{NO} + \text{O} \]

4. **Formation of Ozone**: The free oxygen atom (O) can then react with molecular oxygen (O2) present in the atmosphere to form ozone (O3), which is a significant component of photochemical smog.

- **Reaction**:
\[ \text{O} + \text{O}_2 \rightarrow \text{O}_3 \]

5. **Reduction Process**: In the context of photochemical smog, the reduction refers to the conversion of nitrogen dioxide (NO2) into nitrogen monoxide (NO) as it loses an oxygen atom. This indicates that NO2 is being reduced in the presence of UV light.

6. **Conclusion**: Therefore, the reduction that photochemical smog includes is the conversion of nitrogen dioxide (NO2) to nitrogen monoxide (NO).

**Final Answer**: The reduction involved in photochemical smog is the conversion of nitrogen dioxide (NO2) to nitrogen monoxide (NO).

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