AQA GCSE Chemistry Chemistry Paper 2 (Foundation), June 2025: Question 7

9 marks · Standard Demand difficulty · Short Answer

Calculate gold mass and ratio in an 18 carat gold ring, identify alloy components, and explain why 18 carat gold is harder than pure gold.

Practise this question

Question

Question 7 features 5 parts about gold and its alloys. Sub-question 7.1 asks to calculate the mass of gold in a 4 g jewellery ring containing 75% gold. Sub-question 7.2 asks for the simplest whole-number ratio of mass of gold to other metals. Sub-question 7.3 asks to select two metals other than gold that may be present in 18 carat gold from Copper, Magnesium, Potassium, Silver, and Sodium. Sub-question 7.4 shows Figure 6, illustrating the atomic arrangement of 18 carat gold with distorted layers containing different sized atoms alongside 24 carat gold with regular layers of identical atoms, asking why 18 carat gold is harder. Sub-question 7.5 asks for one reason why iron is not used to make jewellery.
Question text

07 This question is about gold.

18 carat gold is an alloy containing 75% by mass of gold.

07.1 Calculate the mass of gold in a 4 g jewellery ring made from 18 carat gold.

[2 marks]

Mass = g

07.2 What is the simplest whole-number ratio of the mass of gold : mass of other metals

in 18 carat gold?

[1 mark]

Tick ( ) one box.

1 : 3 3 : 1 6 : 18 18 : 6

07.3 What other two metals may also be present in 18 carat gold?

[2 marks]

Tick ( ) two boxes.

Copper

Magnesium

Potassium

Silver

Sodium 25

07.4 Figure 6 represents the structure of 18 carat gold and of 24 carat gold.

Figure 6

Explain why 18 carat gold is harder than 24 carat gold.

[3 marks]

07.5 Gold is used to make jewellery.

Give one reason why iron is not used to make jewellery.

[1 mark]

Mark scheme

Show the mark scheme Mark scheme for Question 7: 07.1 awards 2 marks for (75/100) x 4 = 3 (g). 07.2 awards 1 mark for 3:1. 07.3 awards 2 marks for copper and silver. 07.4 awards 3 marks for: 18 carat gold contains different sized atoms, so layers are distorted, so layers of atoms slide less easily or cannot slide over each other. 07.5 awards 1 mark for iron rusts or aesthetic reasons. Total marks: 9.

Question 7

AO /

Question Answers Extra information Mark

Spec. Ref.

07.1 75 1

(mass =) x 4

100 AO2

4.10.3.2

= 3 (g)

AO /

Spec. Ref.

07.2 3 : 1 1 AO2

4.10.3.2

AO /

Spec. Ref.

07.3 copper 1 AO1

4.10.3.2

silver 1

AO /

Spec. Ref.

07.4 (18 carat gold) contains different 1 AO2

sized atoms 4.2.2.7

4.10.3.2

(so the) layers are distorted 1

(so the) layers (of atoms) slide allow (so the) atoms cannot 1

less easily slide over each other

AO /

Spec. Ref.

07.5 any one from: 1 AO2

• iron rusts 4.10.3.1

• aesthetic reasons 4.10.3.2

Total Question 7 9

How to answer it

Gold Alloys and Metallic Structure

OVERVIEW & SPECIFICATION

What this question tests

This question covers AQA GCSE Chemistry Sections 4.2.2 (Structure and bonding of metals and alloys) and 4.10.3 (Alloys as useful materials).

  • Quantitative Chemistry: Calculating mass from percentages and determining simplest whole-number ratios.
  • Factual Recall: Identifying common alloying elements blended with gold (copper and silver).
  • Structural Explanation: Explaining why alloys are harder than pure metals using ideas of atom sizes, distorted layers, and resistance to sliding.
  • Material Properties: Explaining why pure metals like iron are unsuitable for decorative jewellery (corrosion/rusting).
PART 07.1 • 2 MARKS

Calculating the Mass of Pure Gold

Calculate the mass of gold in a 4 g jewellery ring made from 18 carat gold (75% gold by mass).

📐 Step-by-Step Calculation

  1. Identify percentage & total mass:
    Percentage = 75%
    Total mass = 4 g
  2. Set up calculation:
    (75 ÷ 100) × 4 g or 0.75 × 4 g
  3. Compute final value:
    Mass = 3 g
Mark Scheme Breakdown:
[1 Mark] For correct working: (75 / 100) × 4
[1 Mark] For correct final mass: 3 (g)

❌ Common Calculation Errors

  • Dividing incorrectly: Some students invert the operation and calculate 4 ÷ 75 , resulting in nonsensical tiny values.
  • Omitting working: Writing down an incorrect number without working scores 0 marks. Always write 0.75 × 4 to guarantee a method mark even if an arithmetic slip occurs.
  • Wrong units: The answer line specifies grams (g). Do not convert to milligrams unless asked!
PART 07.2 • 1 MARK

Simplest Whole-Number Ratio of Metals

Simplest whole-number ratio of mass of gold : mass of other metals in 18 carat gold

✅ Correct Answer

Tick box: 3 : 1

Because 18 carat gold is 75% gold, the other metals account for 100% − 75% = 25% .
Ratio = 75 : 25 = 3 : 1 .

🧠 Exam Technique: Checking Order

Always double-check the order stated in the question stem:

Gold : Other metals

  • Gold is the major component (75%), so the larger number must come first.
  • Selecting 1 : 3 is an upside-down trap!
  • Selecting 18 : 6 is mathematically equal, but the question specifies simplest whole-number ratio (divided by 6).
PART 07.3 • 2 MARKS

Identifying Alloying Elements in Gold

What other two metals may also be present in 18 carat gold?

✅ Correct Answers (Tick 2 Boxes)

  • ☑ Copper [1 mark]
  • ☑ Silver [1 mark]

Options: Copper, Magnesium, Potassium, Silver, Sodium

💡 Key Knowledge: Why Copper and Silver?

Pure gold (24 carat) is too soft for everyday wearable jewellery. It is alloyed with copper, silver, and zinc to increase hardness and durability:

  • Reactivity Context: Sodium and potassium are Group 1 alkali metals; they react violently with water and moisture on human skin!
  • Unreactive nature: Jewellery metals must be unreactive, corrosion-resistant transition/precious metals.
PART 07.4 • 3 MARKS

Explaining Why Alloys Are Harder (Figure 6)

Explain why 18 carat gold is harder than 24 carat gold.

✅ Model Answer (Full 3 Marks)

  • Point 1: 18 carat gold contains atoms of different sizes. [1 mark]
  • Point 2: This distorts the regular layers of gold atoms. [1 mark]
  • Point 3: Therefore, the layers slide less easily over each other (or cannot slide easily). [1 mark]

🧠 Exam Technique: The 3-Step Template

Whenever GCSE exams ask why any alloy is harder/stronger than a pure metal, write this 3-step sequence:

  1. Different sized atoms...
  2. ...distort the regular layers...
  3. ...preventing / making it harder for layers to slide over each other.

❌ Common Misconceptions & Examiner Warnings

  • Confusing molecules/ions with atoms: Mentioning "different sized molecules" or "compounds" loses Mark 1. Alloys are mixtures of atoms.
  • Talking about bonding strength: Saying "the bonds are stronger" or "the covalent bonds hold them" scores 0 marks. Hardness in alloys is purely about layers sliding, not bond strengths.
  • Missing the word "layers": Just saying "the atoms cannot slide" is accepted on this mark scheme, but top candidates consistently say "layers cannot slide".
PART 07.5 • 1 MARK

Suitability of Metals for Jewellery

Give one reason why iron is not used to make jewellery.

✅ Acceptable Answers (Any One)

  • Iron rusts / corrodes (in the presence of water and oxygen). [1 mark]
  • Aesthetic reasons (it discolours skin, stains clothes, or looks dull). [1 mark]

💡 Chemical Context: Rusting vs Oxidation

Rusting is specifically reserved for the corrosion of iron and steel:

Iron + Water + Oxygen → Hydrated Iron(III) Oxide

Gold does not react with oxygen or moisture at room temperature, remaining shiny forever. Iron rusts away and forms an unsightly, flaky orange-brown coat.

Topics

Chemistry · C2: Bonding, Structure and the Properties of Matter · C10: Using Resources

Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 2 (Foundation), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.