AQA GCSE Chemistry Chemistry Paper 1 (Foundation), June 2025: Question 10

11 marks · Standard Demand difficulty · Short Answer

Explain metal extraction, compare transition metals with Group 1 metals, and calculate atom economy and conservation of mass for industrial reactions.

Practise this question

Question

Question 10 containing six sub-questions: 10.1 asks which substance is reduced in the reaction SnO2 + C -> Sn + CO2 and to give a reason in terms of oxygen (2 marks). 10.2 asks why carbon can be used to extract tin from tin oxide (1 mark). 10.3 gives the reaction CdO + C -> Cd + CO and asks to calculate the percentage atom economy for the production of cadmium given Ar(C) = 12, Ar(Cd) = 112, and Mr(CdO) = 128 (3 marks). 10.4 asks for two differences between the properties of tungsten (a transition metal) and potassium (a Group 1 metal) (2 marks). 10.5 asks to show that the equation WO3 + 3 H2 -> W + 3 H2O obeys the law of conservation of mass, providing Ar and Mr values (2 marks). 10.6 asks why it is important to use reactions with a high atom economy in industry (1 mark).
Question text

10 This question is about metals and metal oxides.

Tin (Sn) is extracted from tin oxide using carbon.

The equation for the reaction is:

SnO2 + C ⟶ Sn + CO2

10.1 Which substance is reduced in this reaction?

Give one reason for your answer.

Answer in terms of oxygen.

[2 marks]

Substance reduced

Reason

10.2 Why can carbon be used to extract tin from tin oxide?

[1 mark]

10.3 Cadmium (Cd) can be extracted by the reaction of cadmium oxide with carbon.

The equation for the reaction is:

CdO + C ⟶ Cd + CO

Calculate the percentage atom economy for the production of cadmium in

this reaction.

Relative atomic masses (Ar): C = 12 Cd = 112

Relative formula mass (Mr): CdO = 128

[3 marks]

Percentage atom economy = %

10.4 Tungsten is a transition metal.

Potassium is a Group 1 metal.

Give two differences between the properties of tungsten and

the properties of potassium.

[2 marks]

Tungsten oxide reacts with hydrogen to give tungsten (W) and water.

10.5 The equation for the reaction is:

WO3 + 3 H2 ⟶ W + 3 H2O

The law of conservation of mass states:

*38* ‘The mass of the products equals the mass of the reactants during a

chemical reaction.’

Show that the equation obeys the law of conservation of mass.

Relative atomic mass (Ar): W = 184

Relative formula masses (Mr): H2 = 2 WO3 = 232 H2O = 18

[2 marks]

10.6 The reaction producing tungsten has a high atom economy.

Why is it important to use reactions with a high atom economy in industry?

[1 mark]

Mark scheme

Show the mark scheme Mark scheme for Question 10: 10.1 gives 1 mark for SnO2 (tin oxide) and 1 mark for losing oxygen. 10.2 gives 1 mark for carbon being more reactive than tin. 10.3 awards 1 mark for calculating total Mr = 140, 1 mark for setting up (112/140) * 100, and 1 mark for the final answer 80%. 10.4 awards 2 marks for any two properties comparing tungsten to potassium (higher melting/boiling point, denser, harder, stronger, less reactive, ions with different charges, forms coloured compounds, can be a catalyst). 10.5 awards 1 mark for showing mass of reactants = 232 + (3 * 2) = 238 and 1 mark for mass of products = 184 + (3 * 18) = 238. 10.6 awards 1 mark for sustainable development, economic reasons, minimising use of resources, energy, or waste. Total marks: 11.

Question 10

AO /

Question Answers Extra information Mark

Spec. Ref.

10.1 (substance reduced)

SnO2 allow tin oxide 1 AO2

4.4.1.1

4.4.1.3

(reason)

(SnO2) loses oxygen allow (tin oxide) loses oxygen 1

MP2 is dependent upon MP1

being awarded

AO /

Spec. Ref.

10.2 carbon is more reactive than tin allow tin is less reactive than 1 AO3

carbon 4.4.1.2

4.4.1.3

AO /

Spec. Ref.

10.3 (total Mr = 128 + 12 =) 140 allow (total Mr = 112 + 12 + 16 1 AO2

=) 140 4.3.3.2

(% atom economy =)

112 allow correct use of an 1

×100 incorrectly determined total M

140 r

= 80 (%) 1

AO /

Spec. Ref.

10.4 allow the converse for

potassium

allow the transition metal for

tungsten

allow the Group 1 metal for

potassium

ignore references to atomic

structure

any two from: 2 AO1

4.1.2.5

tungsten 4.1.3.1 27

• has a higher melting / boiling 4.1.3.2

point

• is denser

• is harder allow is less malleable / ductile

• is stronger

• is less reactive allow specific reactions showing

difference in reactivity

• has ions with different

charges

• forms coloured compounds

• can be a catalyst

AO /

Spec. Ref.

10.5 (sum of relative formula masses allow (sum of relative formula 1 AO2

on left hand side =) masses on left hand side =) 4.3.1.1

232 + (3 × 2) = 238 232 + 6 = 238 4.3.1.2

(is equal to

sum of relative formula masses allow (is equal to 1

on right hand side =) sum of relative formula masses

184 + (3 × 18) = 238 on right hand side =)

184 + 54 = 238

if no other mark awarded,

allow 1 mark for

232 + 6 = 184 + 54

or

28 allow 1 mark for both sides =

AO /

Spec. Ref.

10.6 for sustainable development allow to minimise use of limited 1 AO1

resources 4.3.3.2

allow to minimise use of energy

allow to minimise waste

or

for economic reasons

ignore references to yield

Total Question 10 11

How to answer it

Metals, Reduction, Atom Economy & Conservation of Mass

WHAT THIS QUESTION TESTS

This question evaluates your foundational knowledge of Chemical Changes (extraction of metals, reactivity series, and reduction) and Quantitative Chemistry (atom economy, conservation of mass, and industrial sustainability), alongside physical and chemical properties comparing Transition Metals vs Group 1 Metals.

QUESTION 10.1 • 2 MARKS

Reduction in Metal Extraction

Reaction: SnO₂ + C → Sn + CO₂

✅ Correct Answers

  • Substance reduced: SnO₂ (or tin oxide) [1 mark]
  • Reason: It loses oxygen [1 mark]
Mark scheme note: The second mark is strictly dependent on correctly naming tin oxide as the substance reduced.

❌ Common Errors

  • Writing just "Tin" or "Sn" instead of tin oxide. Tin is the product formed, not the reactant reduced!
  • Giving an electron-based definition like "gains electrons" when the question explicitly asked: "Answer in terms of oxygen."
QUESTION 10.2 • 1 MARK

Extraction Feasibility using Carbon

Explaining why carbon can displace tin

✅ Correct Answer

Carbon is more reactive than tin
(or tin is less reactive than carbon) [1 mark]

💡 Key Knowledge

A metal can only be extracted from its oxide by reduction with carbon if the metal is below carbon in the reactivity series. Carbon displaces the metal to form carbon dioxide.

QUESTION 10.3 • 3 MARKS

Calculating Percentage Atom Economy

Reaction: CdO + C → Cd + CO

🔧 Step-by-Step Calculation

Step 1: Find the total Mr of all reactants.
Mr(CdO) + Ar(C) = 128 + 12 = 140 [1 mark]

Step 2: Apply the atom economy formula.
% Atom Economy = (Mr of desired product ÷ Total Mr of all reactants) × 100
= (112 ÷ 140) × 100 [1 mark]

Step 3: Calculate final percentage.
= 80% [1 mark]

🧠 Exam Technique & Traps

  • Desired product: The question asks for the production of cadmium (Cd, Ar = 112). Do not include CO in the numerator.
  • Total mass: You can sum either the Mr of all reactants or the Mr of all products—they are identical due to conservation of mass.
  • Error carried forward: If you miscalculate the total reactant mass in Step 1, you can still score 2 marks if your remaining calculation is correct.
QUESTION 10.4 • 2 MARKS

Transition Metals vs Group 1 Metals

Contrasting Tungsten (W) and Potassium (K)

✅ Correct Answers (Give any TWO)

Tungsten (transition metal) compared to potassium (Group 1):

  • Has a higher melting point / boiling point
  • Is denser
  • Is harder / stronger (or less malleable/ductile)
  • Is less reactive
  • Forms ions with different charges
  • Forms coloured compounds
  • Can act as a catalyst
Equivalent statements describing potassium (e.g. "potassium is softer / more reactive") are fully acceptable [2 marks].

❌ Common Errors

  • Describing atomic structure (e.g., "potassium has 1 outer electron"): The mark scheme explicitly states ignore references to atomic structure. Stick to observable physical and chemical properties!
  • Vague terms like "tungsten is heavier" (instead of denser) or "tungsten is more resistant" without naming reactivity or hardness.
QUESTION 10.5 • 2 MARKS

Proving Conservation of Mass

Reaction: WO₃ + 3H₂ → W + 3H₂O

🔧 Step-by-Step Proof

Step 1: Total mass of reactants on left-hand side (LHS):
Mr(WO₃) + 3 × Mr(H₂)
= 232 + (3 × 2) = 232 + 6 = 238 [1 mark]

Step 2: Total mass of products on right-hand side (RHS):
Ar(W) + 3 × Mr(H₂O)
= 184 + (3 × 18) = 184 + 54 = 238 [1 mark]

Since 238 = 238, mass is conserved.

❌ Common Errors

  • Forgetting balancing numbers! Students frequently calculate H₂ as 2 instead of 3 × 2 = 6, or H₂O as 18 instead of 3 × 18 = 54.
  • Stating "mass cannot be lost" without doing the math: the question asks you to show that the equation obeys the law using the provided numbers.
QUESTION 10.6 • 1 MARK

Importance of High Atom Economy

Industrial & Environmental Applications

✅ Correct Answer (Any ONE)

  • For sustainable development
  • For economic reasons / reduces production costs
  • To minimise the use of limited / finite resources
  • To minimise waste produced
  • To minimise energy consumption
1 mark total.

🧠 Exam Technique

Do NOT confuse atom economy with percentage yield. The examiner explicitly states: "ignore references to yield".

A reaction can have a 100% yield but still produce huge amounts of useless waste products if the atom economy is low.

Topics

Chemistry · C1: Atomic Structure and the Periodic Table · C3: Quantitative Chemistry · C4: Chemical Changes

Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 1 (Foundation), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.