CAIE A Level Chemistry 9701 · Nitrogen and sulfur
During heavy traffic in a city, the exhaust gases contain nitrogen monoxide, , and unburned hydrocarbons. Sunlight drives the reaction of with oxygen to form nitrogen dioxide, . Suggest how PAN (peroxyacetyl nitrate) forms in this air and why PAN is a cause for concern.
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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