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
At four practical stations, students record these observation; Station II forms a brown deposit on an iron nail in blue solution; Station III decolourises bromine water; Station IV forms scum with soap solution.
Total: 6 marks
(a) Which station contains an acidic sample? (1 mark)
(b) At Station II, identify the brown deposit. (1 mark)
(c) What does Station III show about the carbon compound? (1 mark)
(d) What does Station IV suggest about the water sample? (1 mark)
(e) Write the balanced equation for the reaction most likely occurring at Station II. (2 marks)
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