Case study·Standard multi-step (3/5)·No calculator
Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
In an atmospheric reaction, a trace species reacts with ozone in an elementary step: . The step is followed by fast reactions that regenerate , so a small amount of can influence many ozone molecules.
Total: 4 marks
(a) State the molecularity of the elementary step. (1 mark)
(b) Write the rate law for the elementary step. (1 mark)
(c) Why can a trace amount of influence many molecules? (1 mark)
(d) What collision condition, besides sufficient energy, is required for the step to be effective? (1 mark)
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