Answer: Ground-level ozone (O 3 ) and peroxyacetyl nitrate (PAN), both powerful oxidants formed by UV-driven reactions.
- A Ground-level ozone (O<sub>3</sub>) and peroxyacetyl nitrate (PAN), both powerful oxidants formed by UV-driven reactions
- B High SO<sub>2</sub> concentration combining with atmospheric moisture to form sulphurous acid in typical laboratory settings
- C Soot particles and carbon monoxide produced by incomplete combustion of coal under usual circumstances
- D Nitrogen gas released under high pressure from vehicle exhausts during acceleration according to most researchers
Correct answer: A. Ground-level ozone (O<sub>3</sub>) and peroxyacetyl nitrate (PAN), both powerful oxidants formed by UV-driven reactions
Explanation: Photochemical smog contains O<sub>3</sub> and PAN (peroxyacetyl nitrate), both strong oxidising agents formed when UV drives reactions between NOx and unburnt hydrocarbons. These oxidants crack rubber, damage plant tissue, and cause eye irritation. Classical smog is reducing because SO<sub>2</sub> and carbon particles act as reducing agents.
Classical smog is a reducing mixture of SO₂ and fog, while photochemical smog is an oxidising mixture generated by UV-driven reactions of NOx and hydrocarbons.
Concept context
Understand how human activities alter the atmosphere, water, and soil. Covers air pollutants, smog types, ozone depletion, acid rain, greenhouse effect, water and soil pollution, and the principles of green chemistry.