PAN present in the photochemical smog stands for _____

Answer

To answer the question, "PAN present in the photochemical smog stands for _____," we need to identify what "PAN" represents in the context of environmental chemistry and photochemical smog.

### 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 volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the atmosphere.

2. **Identifying PAN**:
- In the context of photochemical smog, PAN is an acronym that stands for "Peroxyacetyl Nitrate."

3. **Chemical Composition**:
- Peroxyacetyl Nitrate (PAN) is a chemical compound with the formula C2H3NO5. It is formed in the atmosphere through the reaction of nitrogen oxides and volatile organic compounds in the presence of sunlight.

4. **Role of PAN in Smog**:
- PAN is significant because it is a secondary pollutant that can cause respiratory problems and eye irritation. It also contributes to the overall toxicity of photochemical smog.

5. **Final Answer**:
- Therefore, PAN present in the photochemical smog stands for "Peroxyacetyl Nitrate."