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 group compares hydrochloric acid and acetic acid using pH paper. They use separate clean glass rods and match colours immediately.
Total: 3 marks
(a) Which acid should show the lower pH? (1 mark)
(b) Why is same concentration important in this comparison? (1 mark)
(c) Why should separate clean glass rods be used? (1 mark)
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