CAIE A Level Chemistry 9701 · Nitrogen and sulfur
Nitrogen gas is abundant in the atmosphere but is generally unreactive. However, during lightning strikes, nitrogen gas can react with oxygen to form nitrogen monoxide, which is then oxidised to nitrogen dioxide. Explain why nitrogen gas is generally unreactive, and why the high temperature of a lightning strike enables it to react.
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.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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