CAIE A Level Chemistry 9701 · Nitrogen and sulfur
Vehicle exhaust gases release nitrogen monoxide. Rainwater collected in a region with heavy traffic and coal-fired power stations is acidic and contains both nitrate ions and sulfate ions, even though sulfur dioxide reacts only slowly with oxygen in the air on its own.
Compare the direct formation of nitric acid from these nitrogen oxides with their catalytic role in the oxidation of atmospheric sulfur dioxide to sulfate.
6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.