This mini-lesson covers the whole of the CCEA qualitative analysis content: flame tests for metal cations, sodium hydroxide and ammonia solution precipitate tests, the ammonium ion test (a useful extra), the anion tests (halides, sulfate, carbonate) and the five standard gas tests.
Make a guess: how can a few tests name an unknown powder?
Work through each screen, answer the questions as you go (flame colours, precipitate colours and gas tests) and collect ⭐ stars. Press Start when you're ready.
Dip a piece of nichrome wire into concentrated hydrochloric acid (to clean it), then into the solid sample, and hold it in a hot blue Bunsen flame. The metal cation colours the flame:
Watch out: sodium's strong yellow/orange is the colour students most often muddle with calcium's brick red — sodium is more yellow, calcium more orange-red. Potassium's lilac can be masked if sodium is also present.
Add a few drops of sodium hydroxide solution to a solution of the salt. Insoluble metal hydroxides form as coloured precipitates — and the colour names the cation:
Telling the white three apart: Al³⁺, Zn²⁺ and Mg²⁺ all give a white precipitate. Add excess NaOH — Al³⁺ and Zn²⁺ dissolve again (colourless solution) while Mg²⁺ stays as a white solid. To tell Al³⁺ from Zn²⁺, add ammonia solution instead: in excess, zinc hydroxide redissolves but aluminium hydroxide does not.
The ammonium ion (NH₄⁺) is a cation but has no flame colour. Add sodium hydroxide solution and warm gently: ammonia gas is given off.
Don't forget the warming. Without gentle heat the ammonia is not driven off and the litmus stays red. Damp red litmus turning blue shows any alkaline gas; the CCEA test for ammonia gas is a glass rod dipped in concentrated hydrochloric acid, which gives dense white smoke (ammonium chloride).
CCEA tests three kinds of anion. Acidify first to remove interfering ions, then add the test reagent:
Acidify first. Add dilute nitric acid before silver nitrate, and dilute hydrochloric acid before barium chloride. This removes carbonate ions that would otherwise give a false white precipitate.
Tap a test on the left, then its correct result on the right.
CCEA expects you to identify these gases by a simple bench test:
Don't mix up the splints. Hydrogen needs a lighted splint (it pops); oxygen needs a glowing splint (it relights it). Chlorine first turns indicator red because it is acidic, then bleaches it white.
Tap a gas, then tap the box for the result it gives.
Flame tests: Li crimson · Na yellow/orange · K lilac · Ca brick red · Cu(II) blue-green
NaOH precipitates: Cu²⁺ blue · Fe²⁺ green · Fe³⁺ red-brown · Al³⁺/Zn²⁺/Mg²⁺ white (Al³⁺, Zn²⁺ dissolve in excess; with excess ammonia solution only Zn²⁺ redissolves)
Ammonium: NaOH + warm → ammonia, damp red litmus → blue
Halides + AgNO₃: Cl⁻ white · Br⁻ cream · I⁻ yellow
Sulfate + BaCl₂: white · Carbonate + acid: CO₂, limewater milky
Gases: H₂ pop · O₂ relights glowing splint · CO₂ limewater milky · Cl₂ bleaches damp indicator · NH₃ white smoke with a conc. HCl glass rod
You've covered the key ideas in the CCEA qualitative-analysis content — cations, anions and gases. Press Finish to see your score.
You've worked through Tests for Ions & Gases for CCEA GCSE Chemistry. 🎉
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Next: test yourself in the Verify stage.