Of the following, pick out the constituents of a photochemical smog
A. Ozone
B. Nitrogen oxides
C. PAN
D. `H _2SO _4 `
E. DDT
F. BHC
G `CO _2 `

Options

A. A,B,C
B. A,B, C,G
C. B,C,D,G
D. A,B,C,E ,F,G

Answer

To determine the constituents of photochemical smog from the given options, we can follow these steps:

### Step 1: Understand Photochemical Smog
Photochemical smog is a type of air pollution that occurs when sunlight reacts with pollutants such as nitrogen oxides and volatile organic compounds. It typically forms in urban areas with heavy traffic and is characterized by a brownish haze.

**Hint:** Remember that photochemical smog is primarily formed by reactions involving sunlight and specific pollutants.

### Step 2: Analyze Each Option
Now, let's evaluate each option to see if it is a constituent of photochemical smog:

- **A. Ozone (O₃)**: Ozone is a significant component of photochemical smog. It is formed by the reaction of sunlight with pollutants like nitrogen oxides and volatile organic compounds.

**Hint:** Ozone is often referred to as a secondary pollutant formed in the atmosphere.

- **B. Nitrogen oxides (NOₓ)**: These gases are precursors to ozone formation and are indeed a major constituent of photochemical smog.

**Hint:** Think of nitrogen oxides as the initial pollutants that contribute to the formation of smog.

- **C. PAN (Peroxyacetyl Nitrate)**: PAN is a secondary pollutant formed in the atmosphere and is also a component of photochemical smog.

**Hint:** PAN is often formed from reactions involving nitrogen oxides and organic compounds in the presence of sunlight.

- **D. H₂SO₄ (Sulfuric Acid)**: This is not a constituent of photochemical smog; it is primarily associated with acid rain.

**Hint:** Sulfuric acid is more related to industrial pollution and acid rain rather than smog.

- **E. DDT (Dichlorodiphenyltrichloroethane)**: This is an insecticide and does not contribute to photochemical smog.

**Hint:** DDT is a pesticide, not an air pollutant involved in smog formation.

- **F. BHC (Benzene Hexachloride)**: Similar to DDT, BHC is a pesticide and does not contribute to photochemical smog.

**Hint:** Like DDT, BHC is also a chemical used in agriculture, not in air pollution.

- **G. CO₂ (Carbon Dioxide)**: While CO₂ is a greenhouse gas, it is not a direct constituent of photochemical smog.

**Hint:** CO₂ is more related to climate change than to smog formation.

### Step 3: Conclusion
Based on the analysis, the constituents of photochemical smog from the given options are:
- A. Ozone
- B. Nitrogen oxides
- C. PAN

Thus, the correct answer is A, B, and C.

**Final Answer:** A, B, and C are the constituents of photochemical smog.