GCSE Chemistry (AQA) chapter 4: Chemical changes MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
29 exam-style questions on Chemical changes, 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.
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. A strong acid has a pH of 2. It is diluted so that the concentration of H+ ions falls by a factor of 100. What is the new pH?
A
1
B
3
C
4
D
6
Show answer
Answer: C. Each decrease of 1 in pH means ten times more H+ ions, so a factor of 100 (10 × 10) changes the pH by 2: from 2 up to 4.
2. Which salt forms when copper(II) oxide reacts with nitric acid?
A
copper(II) nitrate
B
copper(II) sulfate
C
copper(II) nitride
D
copper(II) chloride
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Answer: A. Nitric acid produces nitrates, hydrochloric acid chlorides and sulfuric acid sulfates. A nitride contains N3− and is not formed.
3. Mg + Cu2+ → Mg2+ + Cu. Which statement is correct?
A
magnesium is reduced by gaining electrons and copper ions are oxidised by losing electrons
B
magnesium is oxidised by losing electrons and copper ions are reduced by gaining electrons
C
magnesium is reduced by losing electrons and copper ions are oxidised by gaining electrons
D
neither is oxidised or reduced because no oxygen is involved in the reaction
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Answer: B. OIL RIG: oxidation is loss of electrons, reduction is gain. Mg loses 2 electrons and Cu2+ gains 2, so both processes happen together.
4. An iron nail is placed in blue copper(II) sulfate solution. What is observed?
A
a brown coating forms on the nail and the blue colour fades
B
a white precipitate forms and the nail slowly dissolves
C
bubbles of hydrogen form on the nail
D
no change, because copper is more reactive than iron
Show answer
Answer: A. Iron is more reactive and displaces copper, which coats the nail. Blue Cu2+ ions are replaced by pale green Fe2+ ions.
5. Which method gives pure crystals of copper(II) sulfate from copper(II) oxide and sulfuric acid?
A
add excess oxide to warm acid, filter, concentrate the filtrate, then leave to crystallise
B
add the acid to excess oxide, evaporate the mixture to dryness, then filter off the solid
C
add excess acid to the oxide, filter, then heat the residue on the filter paper until dry
D
add the oxide until an indicator shows pH 7, then evaporate the mixture to dryness
Show answer
Answer: A. Excess oxide makes sure all the acid is used; filtering removes the unreacted oxide; crystallising from the concentrated filtrate gives pure crystals.
6. In the electrolysis of molten aluminium oxide, 4.0 mol of Al3+ ions are converted into aluminium at the cathode. How many moles of electrons are gained?
A
48 mol
B
12 mol
C
4.0 mol
D
3.0 mol
Show answer
Answer: B. Each ion needs three electrons: Al3+ + 3e− → Al, so 4.0 × 3 = 12 mol of electrons. The electrons are gained by the ions, which is reduction.
7. Zn + H2SO4 → ZnSO4 + H2. What volume of hydrogen forms at room temperature and pressure when 1.3 g of zinc reacts with excess dilute sulfuric acid? (Ar of Zn = 65; 1 mol of gas occupies 24 dm3)
A
0.96 dm3
B
0.48 dm3
C
0.24 dm3
D
0.020 dm3
Show answer
Answer: B. 1.3 ÷ 65 = 0.020 mol Zn, which gives 0.020 mol H2 (1:1). Volume = 0.020 × 24 = 0.48 dm3. 0.020 is the number of moles, not the volume.
8. Mg + 2H+ → Mg2+ + H2. What happens to the hydrogen ions?
A
they are neutralised by hydroxide ions
B
they are displaced without any transfer of electrons
C
they are oxidised by losing electrons
D
they are reduced by gaining electrons
Show answer
Answer: D. Each H+ gains an electron from magnesium to form hydrogen: 2H+ + 2e− → H2. Gain of electrons is reduction.
9. Why is gold found in the Earth as the metal itself?
A
it is very unreactive
B
it is very dense
C
it is reduced by carbon in rocks
D
it has a high melting point
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Answer: A. Gold is so unreactive that it does not combine with oxygen or other elements, so it is found native and only needs separating from rock.
10. The order of reactivity is magnesium > zinc > iron > copper. Which mixture reacts?
A
copper + zinc sulfate solution
B
copper + iron(II) sulfate solution
C
zinc + copper(II) sulfate solution
D
iron + magnesium sulfate solution
Show answer
Answer: C. A metal displaces a less reactive metal from its compound. Zinc is above copper, so it displaces copper. In the others the free metal is less reactive.
29, each with the answer and a short explanation, across 3 topics: 4.4.1 Reactivity of metals, 4.4.2 Reactions of acids, 4.4.3 Electrolysis. Every chapter test draws ten of them, so you can take it many times.
Is the GCSE Chemistry (AQA) chapter 4 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.
