AQA GCSE Trilogy Chemistry Paper 2 Higher June 2025 question paper 8464/C/2H

Dodecane is an alkane.

The general formula for alkanes is C_nH_2n+2

A molecule of dodecane has 12 carbon atoms.

Complete the formula of dodecane.

A student investigated the effect of changing the temperature on the viscosity of dodecane.

Figure 1 shows the apparatus.

This is the method used.

1. Add 100 cm³ of dodecane at 25 °C to the cup.

2. Immediately start a timer.

3. Stop the timer when 40 cm³ of dodecane has been collected in the measuring cylinder.

4. Record the time taken.

5. Repeat steps 1 to 4 using dodecane at different temperatures.

The student used a water bath to heat the dodecane.

Suggest one reason why the student used a water bath instead of a Bunsen burner to heat the dodecane.

Give one control variable used in the investigation.

Figure 2 shows the results.

Predict the time taken to collect 40 cm³ of dodecane at 75 °C.

You should extend the line of best fit on Figure 2.

The higher the viscosity, the slower dodecane flows.

Explain how the trend in Figure 2 shows the effect of an increase in temperature on the viscosity of dodecane.

The proportions of most gases in the Earth’s atmosphere have not changed much for the past 200 million years.

About one-fifth of the atmosphere is oxygen.

Describe the test for oxygen gas.

Give the result of the test.

Table 1 shows the percentages of some gases in the Earth’s early atmosphere and in the Earth’s atmosphere today.

Explain how the percentages of gases have changed from Earth’s early atmosphere to Earth’s atmosphere today.

You should refer to all three gases in Table 1.

Methane is a greenhouse gas.

Give two ways to reduce methane emissions into the atmosphere.

The percentage of sulfur dioxide in the Earth’s atmosphere increased between 1850 and 1980.

Describe how sulfur dioxide emissions are produced.

Give one harmful effect of sulfur dioxide emissions.

Suggest one reason why the percentage of sulfur dioxide in the Earth’s atmosphere has decreased since 1980.

Crude oil is a finite resource found in rocks.

What is meant by a ‘finite’ resource?

Most of the compounds in crude oil are hydrocarbons.

Define the term ‘hydrocarbon’.

Crude oil found in different areas has different compositions.

Table 2 shows the percentage (%) composition of crude oil from one area.

The volume of crude oil is measured in a unit called ‘barrels’.

Calculate the volume of petrol in dm³ in 90 barrels of crude oil.

Give your answer to 3 significant figures.

Fractions from crude oil can be processed to produce many useful materials by the petrochemical industry.

Which is a useful material produced by the petrochemical industry?

Tick () one box.

Catalytic cracking is used to crack hydrocarbons.

Name one other method of cracking hydrocarbons.

Alkanes are produced by cracking.

Hydrocarbon Z is a different type of hydrocarbon to alkanes.

Hydrocarbon Z:

• is also produced by cracking

• can be used to produce polymers.

Describe a test for hydrocarbon Z.

Give the result of the test.

This question is about methanol.

Methanol is used in screenwash.

Screenwash is used to keep car windscreens clean.

Screenwash is a formulation.

Define the term ‘formulation’.

Carbon monoxide and hydrogen are used to produce methanol.

The conditions used in the production of methanol are:

• high temperature

• high pressure

• a catalyst.

The equation for the reaction is:

91 kJ/mol of energy is transferred during the exothermic forward reaction.

How much energy is transferred when methanol is decomposed into carbon monoxide and hydrogen?

Tick () one box.

A scientist developed a principle to predict the effect of changing conditions on a system at equilibrium.

What was the name of the scientist?

What is the effect of increasing the temperature on the proportion of methanol in the equilibrium mixture?

Tick () one box.

What is the effect of using a catalyst on the proportion of methanol in the equilibrium mixture?

Tick () one box.

Explain the effect of increasing the pressure on the proportion of methanol in the equilibrium mixture.

Explain the effect of using a catalyst on the rate of production of methanol.

The catalyst allows the reaction to take place at a lower temperature.

Explain one advantage of using a lower temperature in the production of methanol.

Do not refer to the position of equilibrium in your answer.

Methanol (CH₃OH) can also be produced by reacting carbon dioxide with hydrogen.

Water is the other product of the reaction.

Write a balanced equation for the reaction.

Students investigated the effect of changing the concentration on the rate of chemical reactions.

A student reacted sodium thiosulfate solution with hydrochloric acid.

Figure 3 shows the apparatus.

This is the method used.

1. Measure 50 cm³ of sodium thiosulfate solution into a conical flask.

2. Put the conical flask on a black cross drawn on a piece of paper.

3. Add 10 cm³ of hydrochloric acid to the conical flask.

4. Start a timer.

5. Stop the timer when the cross is no longer visible.

6. Record the time taken.

7. Repeat steps 1 to 6 using different concentrations of sodium thiosulfate solution.

What is the dependent variable in this investigation?

The equation for the reaction is:

Na₂S₂O₃(aq) + 2 HCl(aq) → 2 NaCl(aq) + S(s) + SO₂(g) + H₂O(l)

The mixture becomes cloudy as the reaction takes place.

Explain why the mixture becomes cloudy.

Explain the effect of changing the concentration of the sodium thiosulfate solution on the rate of reaction.

A different student reacted magnesium with hydrochloric acid.

Figure 4 shows the apparatus.

This is the method used.

1. Measure 50 cm³ of hydrochloric acid into a conical flask.

2. Add 0.1 g of magnesium ribbon to the conical flask.

3. Insert the stopper into the conical flask as quickly as possible.

4. Start a timer.

5. Record the volume of gas collected every 20 seconds for 5 minutes.

6. Repeat steps 1 to 5 using different concentrations of hydrochloric acid.

Why is the stopper inserted into the conical flask as quickly as possible in step 3?

The equation for the reaction of magnesium with hydrochloric acid is:

Describe a test for the gas produced in the reaction.

Give the result of the test.

Figure 5 shows the results for one concentration of hydrochloric acid.

Determine the rate of reaction at 75 seconds.

Gold is used in the printed circuit boards found in smartphones.

Figure 6 shows a printed circuit board.

A type of smartphone contains 1.73 × 10^–4 moles of gold.

In one year, a manufacturer sold 2.48 million of this type of smartphone.

Calculate the total mass of gold contained in 2.48 million of these smartphones.

Give your answer in kilograms.

Relative atomic mass (A_r): Au = 197

What is the total number of gold atoms in one of this type of smartphone?

The Avogadro constant = 6.02 × 10²³ per mole

Tick () one box.

The materials in printed circuit boards can be recycled.

Bioleaching is one method used to extract gold from printed circuit boards.

Describe how bioleaching is used to extract gold.

Copper is also extracted using bioleaching.

Copper can also be extracted from low-grade ores using phytomining.

Phytomining has not been widely used to extract copper.

Suggest two reasons why.