Photochemical smog always contains

Options

A. `SO_(2)`
B. `O_(3)`
C. HNO_(3)`
D. All of these

Answer

To answer the question "Photochemical smog always contains," we can break down the information provided in the video transcript into a step-by-step solution.

### 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) in the atmosphere.

**Hint**: Remember that photochemical smog is primarily formed in the presence of sunlight.

2. **Key Components of Photochemical Smog**:
The main components involved in the formation of photochemical smog include nitrogen oxides (NOx), hydrocarbons (which are a type of VOC), and sunlight (UV radiation).

**Hint**: Identify the pollutants that react under sunlight to form smog.

3. **Chemical Reactions**:
When NOx and hydrocarbons react in the presence of sunlight, they lead to the formation of ozone (O3) and peroxyacetyl nitrate (PAN). The reaction can be summarized as follows:
- NOx + hydrocarbons + sunlight → Ozone (O3) + PAN

**Hint**: Focus on the products formed from the reaction of the pollutants.

4. **Identifying the Components**:
From the reaction, we can conclude that ozone (O3) and peroxyacetyl nitrate (PAN) are consistently produced in photochemical smog. Therefore, these two compounds are always present in photochemical smog.

**Hint**: Recall the specific products that are always associated with photochemical smog.

5. **Final Answer**:
Thus, the components that photochemical smog always contains are:
- Ozone (O3)
- Peroxyacetyl nitrate (PAN)

**Hint**: Ensure you remember the two key compounds that define photochemical smog.

### Conclusion:
Photochemical smog always contains ozone (O3) and peroxyacetyl nitrate (PAN).