CC9.1Tests for ions: flame tests for cations; precipitate tests for metal cations; tests for halide, sulfate, carbonate anions

Notes

Hold a nichrome wire in the compound; place in a blue Bunsen flame. Observe flame colour:

Add NaOH solution to a solution of the unknown metal cation:

Ion	Precipitate colour	Soluble in excess NaOH?
Fe²⁺	Green	No
Fe³⁺	Brown/rust	No
Cu²⁺	Blue	No
Al³⁺	White	Yes (amphoteric)
Ca²⁺	White	No
NH₄⁺	—	Releases NH₃ gas (pungent, turns damp red litmus blue)

Sulfate (SO₄²⁻): add dilute HCl then BaCl₂ solution → white precipitate of BaSO₄ (insoluble in HCl).
Halides: add dilute HNO₃ then AgNO₃:
- Cl⁻ → AgCl (white)
- Br⁻ → AgBr (cream)
- I⁻ → AgI (yellow)
Carbonate (CO₃²⁻): add dilute HCl → effervescence; CO₂ turns limewater milky.

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Try each before peeking at the worked solution.

Question 15 marks
Identifying a mystery compound
(5 marks) A white solid gives a yellow flame in a flame test. A solution of the solid gives a white precipitate with barium chloride solution (acidified with dilute HCl).

(a) Name the cation. (1 mark)
(b) Name the anion. (1 mark)
(c) Name the compound. (1 mark)
(d) Write an ionic equation for the precipitate reaction. (2 marks)
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Question 23 marks
Distinguishing Fe²⁺ from Fe³⁺
(3 marks) Describe how to distinguish between iron(II) sulfate and iron(III) sulfate solutions using sodium hydroxide solution.
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AI-generated · claude-opus-4-7 · v3-edexcel-combined-science

CC9.1 — Tests for ions: flame tests and precipitates

7-card SR deck for Edexcel Combined Science topic CC9.1

7 cards · spaced repetition (SM-2)