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
A food preservative slows an oxidation reaction in a packaged sample. In the uncatalysed path, the activation energy is high. With a small amount of inhibitor, fewer effective collisions lead to product formation per second, though the overall reaction remains thermodynamically possible.
Total: 4 marks
(a) Name the kinetic factor mainly changed by the inhibitor. (1 mark)
(b) Does this necessarily change the equilibrium constant? (1 mark)
(c) State what happens to the number of effective collisions per second. (1 mark)
(d) Give one reason why concentration must be controlled while comparing rates. (1 mark)
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