AQA GCSE Trilogy Chemistry Paper 1 Higher November 2020 question paper 8464/C/1H

This question is about the extraction of aluminium.

An aluminium atom is represented as: 27 A l 13 Give the number of electrons and neutrons in the aluminium atom.

Aluminium is extracted by the electrolysis of a molten mixture of aluminium oxide and cryolite. Figure 1 shows the cell used for the electrolysis.

Aluminium is produced by the reduction of aluminium oxide (Al₂O₃). What is meant by the term reduction?

Oxygen is formed at the positive carbon electrodes. Explain why the positive carbon electrodes must be continually replaced.

A substance conducts electricity because of free moving, charged particles. What are the free moving, charged particles in a:

• carbon electrode (made from graphite)

• molten mixture of aluminium oxide and cryolite

• metal wire?

Molten mixture of aluminium oxide and cryolite

This question is about substances with covalent bonding.

Figure 2 shows a ball and stick model of a water molecule (H₂O).

Suggest one limitation of using a ball and stick model for a water molecule.

Ice has a low melting point. Water molecules in ice are held together by intermolecular forces. Complete the sentence. Ice has a low melting point because the intermolecular forces are.

Figure 3 shows the structure of a molecule.

What is the molecular formula of the molecule in Figure 3 ?

Diamond has a giant covalent structure.

What is the number of bonds formed by each carbon atom in diamond? Tick (✓) one box.

Give two physical properties of diamond.

Name two other substances with giant covalent structures.

Some students investigated the thermal decomposition of metal carbonates. The word equation for the reaction is: metal carbonate → metal oxide + carbon dioxide The students made the following hypothesis: ‘When heated the same mass of any metal carbonate produces the same mass of carbon dioxide.’

The students heated a test tube containing copper carbonate. Table 1 shows their results.

Plan a method the students could use to test their hypothesis. You should show how the students use their results to test the hypothesis. You do not need to write about safety precautions.

This question is about acids, alkalis and bases. A student reacted zinc oxide powder with hydrochloric acid to produce zinc chloride solution.

Complete the equation for the reaction by writing the state symbols.

Give one way that the student could speed up the reaction between zinc oxide powder and hydrochloric acid.

Hydrochloric acid was the limiting reactant.

How could the student know when all the hydrochloric acid has reacted?

How could the student obtain zinc chloride solution from the reaction mixture when all the hydrochloric acid has reacted?

Describe how zinc chloride crystals are produced from zinc chloride solution.

Sulfuric acid and sodium hydroxide react to produce sodium sulfate.

Sulfuric acid is gradually added to sodium hydroxide solution. The pH of the mixture changes as the sulfuric acid is added until in excess. Suggest the pH at:

• the start before sulfuric acid is added

• the end when sulfuric acid is in excess.

Complete the symbol equation for the preparation of sodium sulfate. You should balance the equation.

A solution of hydrochloric acid had a hydrogen ion concentration of 1.0 mol/dm³ Water was added to the hydrochloric acid until the pH increased by 1 What was the hydrogen ion concentration of the hydrochloric acid after water had been added? Tick (✓) one box.

A student investigated the temperature change when magnesium was added to copper sulfate solution. This is the method used.

1. Pour 30 cm³ of copper sulfate solution into a polystyrene cup.

2. Measure the temperature of copper sulfate solution every minute for 3 minutes.

3. Add magnesium on the fourth minute.

4. Measure the temperature of the mixture at 5 minutes and then every minute up to 14 minutes.

What is the dependent variable in this investigation?

The student used the results to plot a graph.

Figure 4 shows the graph.

Suggest why the copper sulfate solution was left for four minutes before adding the magnesium.

Complete Figure 4 by:

• drawing a line of best fit through all the points after 7 minutes

• extending the line back to 4 minutes.

The temperature change for the reaction is the temperature difference between the two graph lines at 4 minutes. Determine the temperature change for the reaction. Use Figure 4.

Explain why the temperature of the mixture decreases after 7 minutes.

The student repeated the experiment with an unknown metal Q instead of magnesium. All the other variables were kept the same. The student recorded a smaller temperature change. Suggest the identity of metal Q. Give one reason for your answer.

A copper sulfate solution contained 0.100 moles of copper sulfate dissolved

Calculate the mass of copper sulfate in 30.0 cm³ of this solution. Relative formula mass (M_r): CuSO₄ = 159.5

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 5 shows the results.

What two conclusions can be made from the results? Tick (✓) two boxes.

The gold foil is:

• 4.00 × 10^–7 metres thick

• 2400 atoms thick.

What is the diameter of one gold atom in metres? Give your answer to 3 significant figures.

Gold reacts with the elements in Group 7 of the periodic table. 0.175 g of gold reacts with chlorine. The equation for the reaction is:

Calculate the mass of chlorine needed to react with 0.175 g of gold. Give your answer in mg Relative atomic masses (A_r): Cl = 35.5 Au = 197

This question is about elements. Caesium is in Group 1 of the periodic table.

Explain what happens to caesium atoms and to oxygen atoms when caesium reacts with oxygen to produce caesium oxide. You should answer in terms of electrons.

Explain why caesium is more reactive than sodium. You should answer in terms of electrons.

Figure 6 shows part of Mendeleev’s periodic table.

Explain why the early periodic tables placed iodine (I) before tellurium (Te), but then Mendeleev placed tellurium before iodine.