Answer: Sulphur and nitrogen.
- A Carbon and phosphorus
- B Silicon and chlorine
- C Sulphur and nitrogen
- D Calcium and magnesium
Correct answer: C. Sulphur and nitrogen
Explanation: SO2 (from burning sulphur-containing fuels) and NO2 (from high-temperature combustion) dissolve in rainwater to form H2SO4 and HNO3 respectively. This produces acid rain with pH typically between 4 and 5.6, compared to the normal value of about 5.6 for CO2-saturated rain.
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.