CAIE A Level Chemistry 9701 · Nitrogen and sulfur
Vehicle exhaust gases contain nitrogen monoxide, NO, and unburned hydrocarbons. In bright sunlight, these gases react to form peroxyacetyl nitrate, PAN, a component of photochemical smog. Suggest why PAN forms more readily in bright sunlight than at night.
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.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.