The component that distinguishes classical smog from photochemical smog is__________.

Answer

To solve the question regarding the component that distinguishes classical smog from photochemical smog, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Classical Smog**: Also known as reducing smog, typically found in cool and humid environments. It is characterized by the presence of smoke and fog.
- **Photochemical Smog**: Also known as oxidizing smog, generally found in warm, dry, and sunny climates. It is formed when sunlight reacts with pollutants.

2. **Identify Common Components**:
- Both types of smog contain smoke and fog as their basic components.
- However, they differ in their specific pollutants.

3. **Identify Key Pollutants**:
- **Classical Smog**: The main pollutant in classical smog is sulfur dioxide (SO2).
- **Photochemical Smog**: The primary pollutants in photochemical smog include nitrogen oxides (NO) and other unsaturated hydrocarbons.

4. **Distinguishing Component**:
- The key component that distinguishes classical smog from photochemical smog is sulfur dioxide (SO2), which is present in classical smog but not in photochemical smog.

5. **Conclusion**:
- Therefore, the component that distinguishes classical smog from photochemical smog is **SO2**.

### Final Answer:
The component that distinguishes classical smog from photochemical smog is **SO2**.

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