GCSE Chemistry (AQA) chapter 8: Chemical analysis MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
23 exam-style questions on Chemical analysis, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
4.8.1 Purity, formulations and chromatography10 questions
4.8.2-4.8.3 Tests for gases and ions; instrumental methods13 questions
Ten Chemical analysis questions with answers
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. Why is the start line on chromatography paper drawn in pencil rather than ink?
A
pencil helps the solvent to rise faster up the paper
B
pencil is insoluble, so it does not dissolve and move up the paper
C
ink would react with the paper and change the colours
D
pencil is easier to see than ink against the paper
Show answer
Answer: B. Graphite is insoluble, so the line stays put. An ink line would dissolve and give its own spots, spoiling the result.
2. Solutions containing Al3+, Ca2+ and Mg2+ all give a white precipitate with a little sodium hydroxide solution. How can aluminium be identified?
A
its precipitate is blue when excess sodium hydroxide solution is added
B
its precipitate turns green then brown on standing in air
C
its precipitate dissolves in excess sodium hydroxide solution
D
its solution gives a lilac flame in a flame test
Show answer
Answer: C. Aluminium hydroxide dissolves in excess sodium hydroxide to form a colourless solution; the calcium and magnesium precipitates do not.
3. Which is the test for hydrogen?
A
a lighted splint burns with a squeaky pop
B
a glowing splint relights and burns brightly
C
damp litmus paper is bleached white after some time
D
limewater turns milky when the gas is bubbled through
Show answer
Answer: A. Hydrogen burns rapidly with a pop. A glowing splint relighting is the test for oxygen.
4. In paper chromatography, what is the mobile phase?
A
the solvent, which moves up the paper
B
the paper, which the solvent moves through
C
the spot of ink, which spreads out
D
the pencil line, from which the spots start
Show answer
Answer: A. The solvent moves through the paper and carries the substances; the paper is the stationary phase.
5. Which is an advantage of instrumental methods of analysis compared with chemical tests?
A
they need no expensive equipment, so any school can use them
B
they are always cheaper than doing chemical tests by hand
C
they can only be used on samples that are already pure
D
they are rapid and sensitive, and can use very small samples
Show answer
Answer: D. Instruments can detect very small amounts quickly and accurately, although the equipment is expensive.
6. Which of these is a formulation?
A
sea water collected from the coast, with dissolved salts and gases
B
a piece of copper metal cleaned with sandpaper
C
distilled water made by condensing steam from boiling tap water
D
a paint made from measured amounts of pigment, binder and solvent, mixed for a purpose
Show answer
Answer: D. A formulation is a mixture designed as a useful product, with each part in a measured quantity. Sea water is a mixture, but not a designed one.
7. Dilute hydrochloric acid and then barium chloride solution are added to a solution. A white precipitate forms. Which ion is present?
A
carbonate
B
sulfate
C
chloride
D
iodide
Show answer
Answer: B. Sulfate ions react with barium ions to form white barium sulfate. The acid first removes carbonate ions, which could also give a precipitate.
8. Pure aspirin melts sharply at 135 °C. A student makes aspirin that melts over the range 125–133 °C, then purifies it by recrystallisation. Which result for the purified sample shows that the purification worked?
A
it melts sharply at 135 °C
B
it melts over the range 125–133 °C
C
it melts over the range 130–135 °C
D
it melts sharply at 128 °C
Show answer
Answer: A. A pure substance has a sharp melting point at its known value. A narrower range closer to 135 °C would show improvement but the sample would still be impure, and a sharp melting point at 128 °C would mean a different pure substance.
9. A mixture X is separated by paper chromatography. The solvent front moves 6.0 cm, and X gives two spots at 2.1 cm and 4.5 cm from the start line. In the same solvent, pure dye A has an Rf value of 0.35 and pure dye B has an Rf value of 0.75. What can be concluded?
A
X contains neither dye, because the Rf values change with the distance moved
B
X contains both dye A and dye B
C
X contains only dye A, because its spots are close to the start line
D
X contains only dye B, because its highest spot moved furthest
Show answer
Answer: B. Rf of the lower spot = 2.1 ÷ 6.0 = 0.35, matching A. Rf of the upper spot = 4.5 ÷ 6.0 = 0.75, matching B. With only two spots, X contains A and B. Rf is a ratio, so it stays the same however far the solvent moves.
10. A solid Z dissolves in water. Sodium hydroxide solution added to the solution gives a brown precipitate. Dilute hydrochloric acid and then barium chloride solution added to a fresh sample give a white precipitate. What is Z?
A
copper(II) sulfate
B
iron(II) sulfate
C
iron(III) sulfate
D
iron(III) chloride
Show answer
Answer: C. A brown precipitate with sodium hydroxide shows iron(III) ions. The white precipitate with barium chloride after acid shows sulfate ions. Iron(II) would give a green precipitate and copper(II) a blue one.
23, each with the answer and a short explanation, across 2 topics: 4.8.1 Purity, formulations and chromatography, 4.8.2-4.8.3 Tests for gases and ions; instrumental methods. Every chapter test draws ten of them, so you can take it many times.
Is the GCSE Chemistry (AQA) chapter 8 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
