AQA GCSE Combined Science: Trilogy Chemistry Paper 1 (Foundation), 2020: Question 3

8 marks · Standard Demand difficulty · Short Answer

Answer questions on alpha particle scattering, Group 7 elements, chlorine reaction mass, and calculate the relative formula mass of gold chloride.

Practise this question

Question

A GCSE science question page with several short parts about gold and gold compounds. The top shows a diagram of the alpha particle scattering experiment: an alpha particle beam aimed at a thin square sheet of gold foil, with some paths shown going straight through, some deflected, and labels indicating that most alpha particles are not deflected and one deflected alpha particle is shown. Below, there are multiple choice and fill-in-the-blank questions asking why some alpha particles are deflected, why most are not deflected, and what conclusion can be drawn about the atom. Further questions ask what Group 7 elements are called, which of fluorine, chlorine, or bromine is most reactive with gold, then a mass question stating that 3.94 g of gold reacts with chlorine to produce 6.07 g of gold chloride and asking for the mass of chlorine that reacts. The final part asks for the relative formula mass of AuCl3 using atomic masses Cl = 35.5 and Au = 197, with answer lines provided.
Question text

03 This question is about gold and compounds of gold.

In the alpha particle scattering experiment alpha particles are fired at gold foil.

Alpha particles are positively charged.

Figure 4 shows the results.

Figure 4

03.1 Some alpha particles are deflected.

Complete the sentence.

Choose the answer from the box.

[1 mark]

negatively charged not charged positively charged

Some alpha particles are deflected because

11 .

the nucleus of the atom is

03.2 Why are most alpha particles not deflected?

[1 mark]

Tick ( ) one box.

The atom is a tiny sphere that cannot be divided.

The atom is mainly empty space.

The electrons orbit the nucleus at specific distances.

03.3 What was one conclusion from the alpha particle scattering experiment?

[1 mark]

Tick ( ) one box.

The mass is concentrated at the centre of the atom.

The mass is concentrated at the edge of the atom.

The mass is spread evenly throughout the atom.

Gold reacts with the elements in Group 7 of the periodic table.

03.4 What are Group 7 elements known as?

[1 mark]

Tick ( ) one box.

Alkali metals

Halogens

Noble gases 12

03.5 Fluorine, chlorine and bromine react with gold.

Which element will be the most reactive with gold?

[1 mark]

Tick ( ) one box.

Fluorine Chlorine Bromine

03.6 3.94 g of gold reacts with chlorine to produce 6.07 g of gold chloride.

The word equation for the reaction is:

gold + chlorine → gold chloride

Calculate the mass of chlorine that reacts with 3.94 g of gold.

[1 mark]

Mass = g

03.7 Calculate the relative formula mass (Mr) of gold chloride (AuCl3).

Relative atomic masses (Ar): Cl = 35.5 Au = 197

[2 marks]

Relative formula mass (Mr) =

Mark scheme

Show the mark scheme The mark scheme table lists answers for questions 03.1 to 03.7. It gives 'positively charged' for the alpha particle deflection question, 'the atom is mainly empty space' for why most alpha particles are not deflected, and 'the mass is concentrated at the centre of the atom' as the conclusion from the scattering experiment. It also states that Group 7 elements are 'halogens' and that fluorine is the most reactive. For the mass calculation, the accepted answer is 2.13 g, and for the relative formula mass of AuCl3 it shows the working 197 + (3 × 35.5) or 197 + 106.5, giving 303.5.

AO /

Question Answers Extra information Mark

Spec. Ref.

03.1 positively charged 1 AO2

5.1.1.3

03.2 the atom is mainly empty space. 1 AO2

5.1.1.3

5.1.1.7

03.3 the mass is concentrated at the 1 AO1

centre of the atom. 5.1.1.3

03.4 halogens 1 AO1

5.1.2.6

03.5 fluorine 1 AO1

5.1.2.6

03.6 2.13 (g) 1 AO2

5.3.1.1

03.7 197 + (3 × 35.5) 1 AO2

or 5.3.1.2

197 + 106.5

= 303.5 1

Total 8

How to answer it

Atomic Structure and Reactivity: Gold

What this question tests:

This question assesses your understanding of the Alpha Particle Scattering Experiment (Rutherford model), properties of Group 7 elements (Halogens), and basic chemical calculations involving mass conservation and relative formula mass (Mr).

Part 03.1 - 03.3: The Alpha Particle Scattering Experiment

💡 Key Knowledge

  • Deflection: Alpha particles are positive. They are repelled by the positive nucleus.
  • Empty Space: Most particles pass straight through because the atom is mostly empty space.
  • Mass: The experiment proved the mass of an atom is concentrated in a tiny, dense nucleus at the centre.

✅ Correct Answers

03.1: The nucleus is positively charged.

03.2: The atom is mainly empty space.

03.3: The mass is concentrated at the centre of the atom.

Part 03.4 - 03.5: Group 7 Elements

💡 Key Knowledge

Group 7 elements are the Halogens. Reactivity decreases as you go down the group. Therefore, Fluorine is the most reactive halogen.

✅ Correct Answers

03.4: Halogens

03.5: Fluorine

Part 03.6 - 03.7: Calculations

📐 03.6: Conservation of Mass

The Law: Mass is neither created nor destroyed in a chemical reaction. Total mass of reactants = Total mass of products.

Step 1: Identify the equation: Gold + Chlorine → Gold Chloride

Step 2: Use the values: 3.94g (Gold) + Xg (Chlorine) = 6.07g (Gold Chloride)

Step 3: Subtract: 6.07 - 3.94 = 2.13g

📐 03.7: Relative Formula Mass (Mr)

Step 1: Identify the formula: AuCl₃

Step 2: List the atoms: 1 × Au, 3 × Cl

Step 3: Substitute values: 197 + (3 × 35.5)

Step 4: Calculate: 197 + 106.5 = 303.5

❌ Common Errors

  • 03.6: Forgetting to subtract and instead adding the two numbers together.
  • 03.7: Forgetting to multiply the Chlorine mass by 3 (the subscript).

🧠 Exam Technique

Always show your working for calculations. Even if you make a small arithmetic error, you can often pick up 1 mark for showing the correct method (e.g., writing 197 + 106.5).

Topics

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

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Chemistry Paper 1 (Foundation), 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.