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
Two solutions have initial pH . Solution A is an acetic acid-acetate buffer with equal acid and salt concentrations. Solution B is adjusted to pH using dilute acid only. A small amount of is added to both.
Total: 5 marks
(a) Which solution shows smaller pH change? (1 mark)
(b) Write the main reaction in solution A. (2 marks)
(c) Explain why solution B changes more. (2 marks)
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