This mini-lesson covers the whole of the CCEA qualitative analysis content: flame tests for metal cations, sodium hydroxide precipitate tests, the ammonium ion test, the anion tests (halides, sulfate, carbonate) and the five standard gas tests.
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.
Cations · flame tests
Flame tests for metal ions
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.
Quick check
Which cation?
?A clean nichrome wire dipped in a salt gives a clear lilac flame. Which metal ion is present?
Cations · sodium hydroxide test
Metal hydroxide precipitates
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:
The CCEA cations: Cu²⁺, Fe²⁺, Fe³⁺, Al³⁺, Zn²⁺, Mg²⁺. Al³⁺ and Zn²⁺ redissolve in excess NaOH; Mg²⁺ does not.
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.
Quick check
Reading the precipitate
?Adding sodium hydroxide solution to a salt gives a red-brown precipitate. Which ion is present?
Cation · ammonium ion
The ammonium ion test
The ammonium ion (NH₄⁺) is a cation but has no flame colour. Add sodium hydroxide solution and warm gently: ammonia gas is given off.
NH₄⁺ + warm NaOH → ammonia gas, which turns damp red litmus paper blue (and has a sharp smell).
Don't forget the warming. Without gentle heat the ammonia is not driven off and the litmus stays red. The same litmus result is the standard test for ammonia gas itself.
Anions · halide, sulfate, carbonate
Tests for the negative ions
CCEA tests three anions. Acidify first to remove interfering ions, then add the test reagent:
Halides with silver nitrate: Cl⁻ white, Br⁻ cream, I⁻ yellow. Sulfate with barium chloride: white. Carbonate with dilute acid: CO₂ that turns limewater milky.
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.
Quick check
Name the anion
?A solution is acidified with dilute nitric acid, then silver nitrate is added. A cream precipitate forms. Which ion is present?
Match it
Anion test → result
Tap a test on the left, then its correct result on the right.
Tests for gases
The five gas tests
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.
Quick check
Identify the gas
?A glowing splint is held in a test tube of gas and it relights. Which gas is in the tube?
Sort it
Gas-test match
Tap a gas, then tap the box for the result it gives.
🔥 Splint tests
🟦 Indicator / limewater
Recap
The results to know
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)
Ammonium: NaOH + warm → ammonia, damp red litmus → blue