CognitoTesting for ions — carbonate, sulfate and halide
Cognito · AQA ChemistryChromatography, flame tests and gas tests
Key facts
Pure substances and mixtures — fill in the table
Term
Detail
Pure substance
Mixture
Formulation
Chromatography
Rf
Rf use
Flame tests and gas tests — fill in the table
Ion / gas
Test result
Li⁺ (flame test)
Na⁺ (flame test)
K⁺ (flame test)
Ca²⁺ (flame test)
Cu²⁺ (flame test)
Hydrogen (gas test)
Oxygen (gas test)
Carbon dioxide (gas test)
Chlorine (gas test)
Ammonia (gas test)
Exam questions — 4 questions · 10 marks
⚡ Extended questions included. Read the hint. Show all working. AI marks against the real AQA mark scheme.
1 markRf valueAQA 8462 P2 style
In a chromatography experiment, a substance travels 4.8 cm and the solvent front travels 8.0 cm. What is the Rf value?
A 1.67
B 0.6
C 3.2
D 0.4
1 markFlame testAQA 8462 P2 style
A solution gives a yellow flame in a flame test. Which ion does this indicate?
A Potassium (K⁺)
B Copper (Cu²⁺)
C Lithium (Li⁺)
D Sodium (Na⁺)
4 marksIdentify an unknown saltAQA 8462 P2 style
Describe a series of tests to identify whether an unknown white solid is sodium chloride or potassium chloride. Include the test, expected results, and conclusion for each test. (4 marks)
Hint: Flame test distinguishes Na (yellow) from K (lilac). Both are chlorides so the silver nitrate test cannot distinguish between them — use it to confirm chloride, flame test to confirm the metal.
+40 XP
1 markGas testAQA 8462 P2 style
What is the test for carbon dioxide and what result indicates its presence?
A A burning splint — it ignites with a pop
B A glowing splint — it relights
C Bubble through limewater — it turns milky/cloudy