Which product of incomplete combustion is primarily responsible for giving photochemical smog its yellowish color?

• A. Sulfur dioxide (SO_2)
• B. Carbon monoxide (CO)
• C. Nitrogen dioxide (NO_2)
• D. Ozone (O_3)

Answer: (C)

Verified step by step guidance

1. Understand that photochemical smog is a type of air pollution that results from the reaction of sunlight with certain pollutants, primarily nitrogen oxides and volatile organic compounds.
2. Recognize that incomplete combustion produces several gases, including carbon monoxide (CO), sulfur dioxide (SO_2), and nitrogen oxides (NO_x), among which nitrogen dioxide (NO_2) is a key component.
3. Recall that nitrogen dioxide (NO_2) is a reddish-brown gas that absorbs light in the visible spectrum, which gives photochemical smog its characteristic yellowish-brown color.
4. Note that while ozone (O_3) is also involved in photochemical smog formation, it is not a direct product of incomplete combustion but rather forms through secondary reactions involving NO_2 and sunlight.
5. Conclude that nitrogen dioxide (NO_2) is the primary product of incomplete combustion responsible for the yellowish color of photochemical smog.