S5 Chemistry: Metal Extraction (Paper 2: Intermediate)

2026-11-12

Ten items to go deeper: reactivity and method, the role of carbon monoxide, blast furnace and limestone stoichiometry, anode consumption, yield and percentage by mass, with answers.

Direct answers　Answers in order: harder, carbon is the dividing line, oxidised to carbon dioxide, 1.40 kg, 1.19 kg, 140 g, the carbon is consumed, 5.40 g, 79.9 percent, cryolite is a solvent.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: S5 Chemistry: Metal Extraction
Level	S5

02　Questions (10 items)

FoundationAre the more reactive metals easier to extract from their ores?
FoundationWhat does the position of carbon in the reactivity series tell us about extraction methods?
FoundationWhat happens to carbon monoxide itself in the blast furnace?
IntermediateWhat mass of iron, in kg, can be obtained in theory from 2.00 kg of iron(III) oxide, Fe = 56?
IntermediateIf the actual yield in the previous question is only 85.0 percent, what mass of iron is obtained?
IntermediateWhat mass of calcium oxide forms when 250 g of calcium carbonate decomposes completely, CaCO3 = 100 and CaO = 56?
ChallengeWhy must the carbon anodes in aluminium electrolysis be replaced regularly?
ChallengeWhat mass of aluminium can be obtained in theory from 10.2 g of aluminium oxide, Al2O3 = 102 and Al = 27?
ChallengeWhat is the percentage by mass of copper in copper(II) oxide, Cu = 63.5 and O = 16?
Error redoA student says cryolite is a catalyst that makes aluminium oxide decompose faster. What is wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	No, the more reactive a metal, the harder it is to extract.	Compounds of reactive metals are more stable and need more energy to break down, so electrolysis replaces simple heating with carbon.
2	Carbon is the dividing line: metals above it need electrolysis, metals below it can be reduced by carbon or carbon monoxide.	The method depends on the position of the metal relative to carbon, not on the colour or density of the ore.
3	It is oxidised to carbon dioxide, so it acts as the reducing agent.	A reducing agent is itself oxidised, taking oxygen from the substance it reduces, which is the key to identifying redox.
4	1.40 kg	Iron makes up 0.700 of the mass, and 2.00 kg times 0.700 is 1.40 kg.
5	1.19 kg	Yield is actual over theoretical, and 1.40 times 0.850 gives 1.19.
6	140 g	250 g is 2.50 mol, the ratio is one to one, so 2.50 mol of calcium oxide forms, which is 140 g.
7	Oxygen discharged at the anode reacts with the carbon to form carbon dioxide, so the carbon is consumed.	Oxidation occurs at the anode and the carbon takes part, so the blocks thin away, one of the running costs of aluminium smelting.
8	5.40 g	10.2 g is 0.100 mol and each mole holds two moles of aluminium, giving 0.200 mol, which is 5.40 g.
9	79.9 percent	The molar mass is 79.5 g mol-1 and copper contributes 63.5, so 63.5 over 79.5 is 0.7987.
10	Wrong. Cryolite is a solvent that dissolves the oxide and lowers the melting point; it is not a catalyst and does not change the overall energy needed.	A catalyst changes the rate without being consumed, while cryolite simply provides a molten medium, so the two roles differ.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

Write one sentence on why iron uses carbon while aluminium uses electricity, and name the reactivity series as the key.Tutor Registration →

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