This key facts covers Sequential Testing Strategy within Tests for Ions for GCSE Chemistry. Revise Tests for Ions in Chemical Analysis for GCSE Chemistry with 20 exam-style questions and 14 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 8 of 14 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 8 of 14
Practice
20 questions
Recall
14 flashcards
📋 Sequential Testing Strategy
When identifying an unknown compound, follow this logical order:
- Observe: Note colour, state, and any obvious properties
- Flame test first: Quick visual check for Li⁺, Na⁺, K⁺, Ca²⁺, Cu²⁺
- NaOH test: For transition metal cations and Al³⁺, Ca²⁺
- Add dilute HCl: Does it fizz? If yes, CO₃²⁻ is present
- BaCl₂ + HCl: White precipitate = SO₄²⁻
- AgNO₃ + HNO₃: White/cream/yellow precipitate identifies Cl⁻/Br⁻/I⁻
- Confirm identity: Check that cation + anion combination is chemically sensible
Example: Identifying an Unknown White Solid
- Flame test → red flame (suggests Ca²⁺ or Li⁺)
- Add acid → fizzing; gas turns limewater milky → CO₃²⁻ present
- NaOH → white precipitate that does NOT redissolve (confirms Ca²⁺, not Al³⁺)
- Conclusion: Calcium carbonate (CaCO₃)