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
Three cobalt(III) compounds have the same six-coordinate cobalt centre. Compound I gives three moles of per mole with excess , compound II gives two, and compound III gives one. The formula unit in each case contains cobalt, ammonia and three chloride ions.
Total: 3 marks
(a) Which compound has all three chloride ions outside the coordination sphere? (1 mark)
(b) For compound II, how many chloride ions are inside the coordination sphere? (1 mark)
(c) Write a likely coordination formula for compound III if the coordination number is . (1 mark)
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