Reactivity of metals, extraction & redox – GCSE Chemistry exam questions with mark scheme

1Grade 4–55 marks

A student added three metals, P, Q and R, to solutions of their metal sulfates. A tick (✓) shows a reaction happened.

Metal	P sulfate	Q sulfate	R sulfate
P	—	✗	✓
Q	✓	—	✓
R	✗	✗	—

(a) Put the metals in order of reactivity, most reactive first. [2]

(b) Iron is extracted by heating iron oxide with carbon, but aluminium is extracted by electrolysis. Explain why. [2]

(a) Q most reactive or R least reactive(1)
(a) Q, P, R (complete correct order, most reactive first) allow 1 mark only if correct order given least reactive first (R, P, Q)(1)
(b) iron is less reactive than carbon (so carbon can remove oxygen from / reduce iron oxide) allow carbon is more reactive than iron(1)
(b) aluminium is more reactive than carbon (so carbon cannot reduce aluminium oxide) allow carbon is less reactive than aluminium(1)
(c) loss of oxygen allow removal of oxygen(1)
Answer: (a) Q > P > R (b) carbon is more reactive than iron but less reactive than aluminium (c) loss of oxygen
Examiner tip: Count the ticks in each row: the metal that displaces the most others is the most reactive.

2Grade 1–3Foundation4 marks

A student heats a small piece of calcium in air. The calcium burns with a red flame and a white solid forms.

(a) Name the white solid. [1]

(b) The calcium has been oxidised. Explain why, in terms of oxygen. [1]

$$\ldots\,\text{Ca} + \text{O}_2 \rightarrow \ldots\,\text{CaO}$$

(d) The student then heats some copper foil in air. The surface of the copper turns black. Name the black substance. [1]

(a) calcium oxide allow CaO; ignore lime / quicklime; do not accept calcium hydroxide / calcium carbonate(1)
(b) (the calcium) gains oxygen allow oxygen is added (to the calcium) / combines with oxygen; ignore ‘reacts with oxygen’ / ‘burns’ alone(1)
(c) $2\,\text{Ca} + \text{O}_2 \rightarrow 2\,\text{CaO}$ (both 2s needed) allow multiples(1)
(d) copper oxide allow copper(II) oxide / CuO; do not accept copper carbonate / soot / carbon(1)
Answer: (a) calcium oxide (b) it gains oxygen (c) 2Ca + O₂ → 2CaO (d) copper oxide
Examiner tip: Oxidation in terms of oxygen means gaining oxygen. ‘Burns’ or ‘reacts’ alone does not explain why it is oxidation.

3Grade 1–3Foundation5 marks

The diagram shows part of the reactivity series. Carbon and hydrogen are non-metals but are included for comparison.

(a) Name the metal in the diagram that is found in the Earth as the uncombined element. [1]

(b) Name one metal in the diagram that can be extracted by heating its oxide with carbon. [1]

(d) The reactivity of a metal is related to its tendency to form positive ions. Name the metal in the diagram that forms positive ions most easily. [1]

(e) A student adds iron filings to magnesium sulfate solution. Predict whether a reaction happens. Give a reason for your answer. [1]

(a) gold allow Au(1)
(b) any one of: zinc / iron / copper allow symbols; do not accept any metal above carbon(1)
(c) copper or gold allow symbols; if two metals given both must be correct(1)
(d) potassium allow K(1)
(e) no reaction and iron is less reactive than magnesium (so cannot displace it) allow magnesium is more reactive than iron; no mark for ‘no’ without a reason(1)
Answer: (a) gold (b) zinc, iron or copper (c) copper or gold (d) potassium (e) no — iron is less reactive than magnesium
Examiner tip: For (e), a prediction with no reason scores nothing: compare the positions of the two metals in the series.

4Grade 4–56 marks

A student added small pieces of four metals to cold water and to dilute hydrochloric acid. The table shows the observations.

Metal	Cold water	Dilute hydrochloric acid
calcium	fizzes steadily; solution goes cloudy	fizzes very rapidly
copper	no reaction	no reaction
magnesium	a few bubbles form very slowly	fizzes rapidly
zinc	no visible reaction	bubbles form steadily

(a) Use the table to put the four metals in order of reactivity, most reactive first. [1]

(b) Name the gas produced in the reactions. [1]

(d) Iron is between zinc and copper in the reactivity series. Predict what the student would see when iron is added to:

• cold water

• dilute hydrochloric acid. [2]

(e) Explain why copper does not react with dilute hydrochloric acid. Use the reactivity series. [1]

(a) calcium, magnesium, zinc, copper (all four in order)(1)
(b) hydrogen allow H₂; do not accept H(1)
(c) calcium hydroxide allow Ca(OH)₂; do not accept calcium oxide(1)
(d) cold water: no (visible) reaction allow very slow reaction / rusts slowly; do not accept fizzing(1)
(d) acid: a few bubbles / slow fizzing allow bubbles form slowly / more slowly than zinc; do not accept no reaction(1)
(e) copper is less reactive than hydrogen (so cannot displace hydrogen from the acid) allow copper is below hydrogen in the reactivity series(1)
Answer: (a) Ca > Mg > Zn > Cu (b) hydrogen (c) calcium hydroxide (d) water: no visible reaction; acid: slow bubbling (e) copper is below hydrogen
Examiner tip: In (d), the acid observation must show iron reacts, but more slowly than zinc; ‘no reaction’ with acid loses the mark.

5Grade 4–56 marks

A student investigated the reactivity of four metals using displacement reactions.

This is the method used.

Pour 25 cm³ of copper sulfate solution into a polystyrene cup.
Measure the starting temperature of the solution.
Add 1.0 g of a metal powder and stir.
Record the highest temperature reached.
Repeat with each metal, three times each.

The diagram shows the apparatus. The table shows the results.

Metal	Temperature rise in °C
Metal	Trial 1	Trial 2	Trial 3
iron	6.5	7.0	6.0
magnesium	31.5	32.0	31.0
silver	0.0	0.0	0.0
zinc	12.5	13.5	17.5

(a) Identify the anomalous result in the table. [1]

(b) Calculate the mean temperature rise for zinc. Do not include the anomalous result. [1]

(d) Explain why there was no temperature change with silver. [1]

(e) Give two variables the student kept the same. [2]

(a) 17.5 (°C) for zinc (trial 3) allow zinc trial 3(1)
(b) 13.0 (°C) allow 13; do not accept 14.5 (anomaly included)(1)
(c) magnesium, zinc, iron, silver(1)
(d) silver is less reactive than copper (so it does not displace copper / no reaction happens) allow copper is more reactive than silver; ignore ‘silver is unreactive’ unless compared with copper(1)
(e) any two from: volume of copper sulfate solution (25 cm³); mass of metal (1.0 g); concentration of copper sulfate solution; particle size / metal used as powder; type of cup / insulation; starting temperature (of solution)(1)
(e) second correct variable from the list ignore ‘amount of solution’ / ‘same metal’ / ‘same equipment’(1)
Answer: (a) 17.5 °C for zinc (b) 13.0 °C (c) Mg > Zn > Fe > Ag (d) silver is less reactive than copper (e) e.g. volume of copper sulfate, mass of metal
Examiner tip: A bigger temperature rise means a more vigorous displacement, so the metal is further above copper; ‘unreactive’ for silver needs comparing with copper.

6Grade 4–55 marks

Gold is found in the Earth as the uncombined element. Zinc is found combined with other elements in ores.

(a) Explain why gold is found as the uncombined element. [1]

Zinc is extracted by heating zinc oxide with carbon in a furnace at 1100 °C.

$$\text{ZnO} + \text{C} \rightarrow \text{Zn} + \text{CO}$$

(b) Identify the substance that is oxidised in this reaction. Give a reason for your answer. [2]

(d) A student says: “Zinc oxide is oxidised in this reaction because it reacts with carbon.” Explain why the student is wrong. [1]

(a) gold is (very) unreactive allow gold does not react (easily) with other substances / with oxygen / with water; ignore gold is rare / valuable(1)
(b) carbon allow C(1)
(b) (because) it gains oxygen (to form carbon monoxide) — dependent on carbon identified allow it is converted to CO(1)
(c) the furnace temperature (1100 °C) is above the boiling point of zinc (907 °C) allow zinc boils / evaporates at the furnace temperature(1)
(d) zinc oxide loses oxygen, so it is reduced (not oxidised) allow oxygen is removed from zinc oxide; must refer to loss of oxygen for the mark(1)
Answer: (a) gold is very unreactive (b) carbon — it gains oxygen (c) 1100 °C is above zinc’s boiling point (d) zinc oxide loses oxygen, so it is reduced
Examiner tip: Find the substance that GAINS oxygen (oxidised) and the one that LOSES oxygen (reduced) — the oxide being extracted is always the one reduced.

7Grade 6–7Higher6 marks

Lead is extracted by heating lead(II) oxide with carbon.

$$2\,\text{PbO} + \text{C} \rightarrow 2\,\text{Pb} + \text{CO}_2$$

Relative atomic masses ($A_r$): C = 12 O = 16 Pb = 207

(a) Calculate the maximum mass of lead that can be produced from 44.6 kg of lead(II) oxide. [3]

(b) Calculate the minimum mass of carbon needed to react with 44.6 kg of lead(II) oxide. [2]

(a) $M_r$ of PbO = 223(1)
(a) moles of PbO = 44 600 ÷ 223 = 200 (mol) allow 44.6 ÷ 223 = 0.2 (kmol) / ratio method: 2 × 223 = 446 kg PbO gives 2 × 207 = 414 kg Pb(1)
(a) mass of Pb = 200 × 207 = 41 400 g = 41.4 kg allow 41 400 g; correct answer with no working scores 3(1)
(b) moles of C = 200 ÷ 2 = 100 (mol) allow ecf from moles of PbO in (a); allow ratio: 446 kg PbO reacts with 12 kg C(1)
(b) mass of C = 100 × 12 = 1200 g = 1.2 kg allow 1200 g; correct answer with no working scores 2(1)
(c) lead(II) oxide allow lead oxide / PbO / lead(II) ions / Pb²⁺; do not accept lead / Pb / carbon(1)
Answer: (a) 41.4 kg (b) 1.2 kg (c) lead(II) oxide
Examiner tip: Keep the units consistent: convert kg to g before dividing by M_r, then convert back, or work in kmol throughout. Use the 2 : 1 ratio for carbon.

8Grade 6–7Higher6 marks

The thermite reaction is used to produce molten iron for welding railway tracks.

$$2\,\text{Al} + \text{Fe}_2\text{O}_3 \rightarrow \text{Al}_2\text{O}_3 + 2\,\text{Fe}$$

(a) Explain why aluminium can displace iron from iron(III) oxide. [1]

(b) In terms of oxygen, name the substance that is reduced. [1]

$$\text{Fe}^{3+} + \ldots \rightarrow \text{Fe}$$

(d) Write a half equation for the change that happens to aluminium atoms. [1]

(e) Explain why aluminium is oxidised, in terms of electrons. [1]

(f) Iron is extracted on a large scale by reduction with carbon, not by the thermite reaction. Suggest why. [1]

(a) aluminium is more reactive than iron allow iron is less reactive than aluminium; do not accept ‘aluminium is reactive’ (no comparison)(1)
(b) iron(III) oxide allow iron oxide / Fe₂O₃; do not accept iron / aluminium(1)
(c) $3\text{e}^-$ allow 3e(1)
(d) $\text{Al} \rightarrow \text{Al}^{3+} + 3\text{e}^-$ allow $\text{Al} - 3\text{e}^- \rightarrow \text{Al}^{3+}$; allow multiples; ignore state symbols(1)
(e) aluminium (atoms) lose electrons allow each Al atom loses three electrons; do not accept ‘gains oxygen’ (not in terms of electrons) / ‘aluminium ions lose electrons’(1)
(f) aluminium is more expensive than carbon allow aluminium is extracted by electrolysis, which uses a lot of energy / carbon (coke) is cheaper; ignore ‘thermite is dangerous’ alone(1)
Answer: (a) Al more reactive than Fe (b) iron(III) oxide (c) 3e⁻ (d) Al → Al³⁺ + 3e⁻ (e) Al atoms lose electrons (f) aluminium costs more than carbon (made by energy-hungry electrolysis)
Examiner tip: OIL RIG: the species that loses electrons is oxidised. In (e) the answer must use electrons, not oxygen.

9Grade 6–7Higher6 marks

Copper can be produced by two different methods.

Method 1: copper oxide (from a high-grade ore) is heated with carbon in a furnace.

$$2\,\text{CuO} + \text{C} \rightarrow 2\,\text{Cu} + \text{CO}_2$$

Method 2: a low-grade ore is treated to make copper sulfate solution. Scrap iron is added to the solution.

$$\text{Fe} + \text{CuSO}_4 \rightarrow \text{FeSO}_4 + \text{Cu}$$

The table gives information about the two methods.

	Method 1	Method 2
Temperature	about 1100 °C	room temperature
Energy used per tonne of copper in GJ	25	8
Type of ore	high-grade (rich in copper)	low-grade (little copper)
Purity of copper produced	98%	85% (mixed with iron)
Waste products	carbon dioxide	iron sulfate solution

Evaluate the two methods of producing copper.

In your answer you should explain the chemistry of each method in terms of reactivity and oxidation and reduction. [6]

Chemistry, Method 1: carbon is more reactive than copper, so carbon can remove oxygen from copper oxide(1)
copper oxide loses oxygen so is reduced; carbon gains oxygen so is oxidised (to carbon dioxide)(1)
Chemistry, Method 2: iron is more reactive than copper, so iron displaces copper from copper sulfate (solution)(1)
iron atoms lose electrons / are oxidised; copper ions gain electrons / are reduced(1)
For Method 1: copper is purer (98%), so needs less further purification(1)
Against Method 1: high temperature, so uses more energy (25 GJ vs 8 GJ per tonne) / higher fuel cost(1)
releases carbon dioxide, a greenhouse gas (contributes to climate change)(1)
needs high-grade ore, which is running out / limited supply(1)
For Method 2: less energy (about a third) / works at room temperature(1)
uses low-grade ore, so conserves high-grade ore / uses waste ores(1)
uses scrap iron, so recycles waste metal; no carbon dioxide produced(1)
Against Method 2: copper is less pure (85%, contains iron), so needs purifying (which uses more energy)(1)
iron sulfate solution must be disposed of or treated(1)
Judgement: a justified conclusion, e.g. Method 2 is better overall because it uses less energy, uses low-grade ore and scrap and makes no CO₂, even though the copper must be purified; or Method 1 if high purity is the priority(1)

Level	Marks	What it looks like
Level 3	5–6	Explains the chemistry of both methods correctly using reactivity and oxidation/reduction. Gives advantages and disadvantages of both methods, using the data to compare them, and reaches a conclusion that is justified by the points made.
Level 2	3–4	Some correct chemistry for at least one method (e.g. a correct reactivity comparison or identification of what is reduced). Several relevant advantages or disadvantages, though comparison may be one-sided or the conclusion missing or not fully supported.
Level 1	1–2	Simple, isolated statements about the methods, mostly lifted from the table, with little or no chemistry and no comparison or conclusion.
No relevant content	0	No relevant content.

Answer: Both work because the reducing substance (C or Fe) is more reactive than copper. Method 1: purer copper but high energy, CO₂ and needs scarce high-grade ore. Method 2: less energy, low-grade ore and recycled iron, no CO₂, but impure copper and iron sulfate waste. Justified judgement.
Examiner tip: ‘Evaluate’ needs points for and against BOTH methods and a final judgement backed by the data; copying the table without comparing will not get past Level 2.

10Grade 8–9Higher7 marks

A student places a coil of copper wire in colourless silver nitrate solution and leaves it for an hour.

$$\text{Cu} + 2\,\text{AgNO}_3 \rightarrow \text{Cu(NO}_3)_2 + 2\,\text{Ag}$$

(a) Describe two observations the student would make. [2]

(b) Another student wrote this ionic equation for the reaction.

$$\text{Cu} + \text{Ag}^+ \rightarrow \text{Cu}^{2+} + \text{Ag}$$

Explain why this ionic equation is incorrect, and write the correct ionic equation. [2]

(d) Explain why nitrate ions are not included in the ionic equation. [1]

(a) solution turns blue allow colourless to blue / pale blue; do not accept green(1)
(a) silver / grey (shiny) solid / crystals form on the wire allow wire becomes coated / copper wire gets thinner; ignore ‘silver forms’ without an observation(1)
(b) the charges do not balance allow left side has total charge +1 and right side +2 / one Cu atom loses 2 electrons but one Ag⁺ gains only 1(1)
(b) $\text{Cu} + 2\text{Ag}^+ \rightarrow \text{Cu}^{2+} + 2\text{Ag}$ allow multiples; ignore state symbols(1)
(c) copper (atoms) are oxidised because they lose electrons allow Cu → Cu²⁺ + 2e⁻ with ‘oxidised’(1)
(c) silver ions are reduced because they gain electrons allow Ag⁺ + e⁻ → Ag with ‘reduced’; do not accept ‘silver is reduced’ unless ions specified(1)
(d) they are spectator ions / they do not change (during the reaction) allow they are the same on both sides / not involved in the reaction(1)
Answer: (a) solution turns blue; silver-grey crystals form on the wire (b) charges not balanced: Cu + 2Ag⁺ → Cu²⁺ + 2Ag (c) Cu atoms lose electrons (oxidised); Ag⁺ ions gain electrons (reduced) (d) spectator ions — unchanged
Examiner tip: An ionic equation must balance charge as well as atoms: each Cu loses 2 electrons, so 2 Ag⁺ are needed to take them.

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