Case study·Hard exam skill (4/5)·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 health worker prepares an oral rehydration solution by dissolving salts in water and making the final volume . The solution must be uniform before it is given.
Total: 4 marks
(a) Calculate the mass by volume percentage of salts. (2 marks)
(b) Why should the final mixture be uniform? (1 mark)
(c) Name one error in preparation that would change the concentration. (1 mark)
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