CAIE A Level Chemistry 9701 · Reaction kinetics
Chlorine atoms catalyse the decomposition of ozone in the stratosphere. The uncatalysed reaction has a high activation energy. With chlorine atoms present, the reaction follows a different mechanism with a lower activation energy.
Compare the catalysed and uncatalysed reactions in terms of their activation energies, the effect on the Boltzmann distribution, and the reaction pathway diagram.
5 marks, so the mark scheme is looking for about 5 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.
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