CAIE A Level Chemistry 9701 · Nitrogen and sulfur
Photochemical smog forms in urban areas on hot sunny days. A major component of photochemical smog is peroxyacetyl nitrate (PAN). Suggest how PAN is formed from the atmospheric pollutants produced by internal combustion engines, and explain why its formation is a problem.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Suggest means: Apply what you know to an unfamiliar situation. There may be more than one acceptable answer. Reason from the principle you have learned to the new context, and say which principle you are using.
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