AQA A Level Chemistry Paper 2 June 2025 question paper 7405/2

This question is about different ways to make 1,2-dichlorobutane.

Give the name of the mechanism for reaction 1.

State one essential condition needed for reaction 1.

Name of mechanism

Essential condition

Give equations to show three essential steps in the mechanism for reaction 1.

Suggest two reasons why using reaction 1 is likely to give a low yield of 1,2-dichlorobutane.

Give a suitable reagent and conditions needed for reaction 2.

Identify the reagent and name the mechanism for reaction 3.

Name of mechanism

Use of the reagent for reaction 2 followed by the reagent for reaction 3 gives another organic product.

Give the structure of the other organic product.

This question is about isomerism.

Compound L has this structure.

Use IUPAC rules to name L.

Explain why L exists as stereoisomers.

Compound M has the same carbon chain as L but the double bond is in a different position.

M also exists as stereoisomers.

Draw the structural formula of M.

Explain why M exists as stereoisomers.

Structural formula

Figure 1 shows part of the mechanism when L reacts with hydrogen bromide.

Complete Figure 1 to show the next step in the mechanism that gives the

This question is about polymers.

A section of the polymer PVC is shown.

Name the monomer used to make PVC.

Draw the structure of the monomer used to make PVC.

Structure

State why PVC is not biodegradable.

Diisobutyl phthalate (DIBP) is a plasticiser added to PVC to modify its properties.

State how the properties of PVC are modified by the addition of DIBP.

An incomplete equation for the reaction used to make DIBP is shown.

Complete the equation.

Give the name of the mechanism for this reaction.

Deduce the empirical formula of DIBP.

Empirical formula of DIBP

A different plasticiser, DEHA, is added to PVC used for food packaging.

The structure of DEHA is

Identify the organic compound that would react with hexanedioic acid to form DEHA.

DEHA can be absorbed into food from PVC packaging.

In an investigation, 1 kg samples of three different foods are stored in PVC packaging for 30 days.

Table 1 shows the water content, fat content and mass of DEHA in each type of food after 30 days.

Use your knowledge of intermolecular forces to explain these results.

The polymer nylon 6,6 can be made from hexanedioyl dichloride and hexane-1,6-diamine.

Figure 2 shows an incomplete mechanism for the first steps in this reaction.

Draw the missing intermediate in the box in Figure 2.

Complete Figure 2 by adding the curly arrows and any relevant lone pairs of electrons involved in these steps in the mechanism.

The polymer nylon 6 can be made by heating caprolactam with water.

Figure 3 shows the species involved in the first three steps of the mechanism for this reaction.

Complete Figure 3 by adding the curly arrows and any relevant lone pairs of electrons involved in these steps in the mechanism.

Hexanedioic acid is an important compound used in organic synthesis.

Hexanedioic acid can be prepared from cyclohexanol.

The equation for the reaction is

C₆H₁₁OH(l) + 2 HNO₃(aq) HOOC(CH₂)₄COOH(s) + N₂O(g) + 2 H₂O(l)

Method

Step 1 Add 5 cm³ of concentrated nitric acid to a boiling tube.

Step 2 Place the boiling tube in a beaker of water at 85 °C

Step 3 Add 2 cm³ of cyclohexanol dropwise to the boiling tube.

Step 4 Leave the reaction mixture for 10 minutes.

Step 5 Cool the boiling tube in a beaker of cold water for a further 10 minutes.

Step 6 Filter the contents of the boiling tube and collect the impure solid.

Step 7 Recrystallise the impure solid using methanol.

Step 8 Wash the purified crystalline product with some ice-cold distilled water, and dry.

Step 9 Measure the melting point of the hexanedioic acid.

Suggest why the apparatus should be set up in a fume cupboard.

Deduce the role of the concentrated nitric acid in the reaction.

Outline how Steps 7 and 8 should be done to obtain the purified crystalline product.

In Step 8, the distilled water must be ice-cold.

Suggest why using water at room temperature lowers the recorded yield of product.

Figure 4 shows how a student set up the apparatus for measuring the melting point of hexanedioc acid in Step 9 (data book value 152 °C).

The apparatus is supported by clamps but these are not shown.

Identify two mistakes the student made in setting up this apparatus.

State the problem caused by each mistake.

Figure 5 shows an alternative process to make hexanedioic acid.

Scientists disagree about whether this alternative process is more sustainable or less sustainable than the process starting from cyclohexanol.

Use the information given in Figure 5 to provide a justification for each point of view.

This question is about making the explosive 2-methyl-1,3,5-trinitrobenzene, commonly known as TNT.

TNT can be made by reacting methylbenzene with concentrated nitric acid in the presence of concentrated sulfuric acid.

Give the overall equation for the reaction between methylbenzene and nitric acid.

The yield of TNT in this reaction is 42.5%.

Calculate the mass, in g, of TNT (M_r = 227.0) obtained from

Methylbenzene has density = 0.867 g cm^–3 and M_r = 92.0

In the mechanism for this reaction, concentrated nitric acid reacts with concentrated sulfuric acid to produce the nitronium ion O₂N⁺

Give an equation for the reaction to produce the nitronium ion.

State the role of the nitronium ion in the reaction with methylbenzene.

Outline the mechanism for the reaction of the nitronium ion with methylbenzene to give 2-methyl-1-nitrobenzene.

Equation

Role of nitronium ion

Mechanism

GHK is a natural tripeptide found in human blood plasma.

The amino acid sequence of GHK is Lys-His-Gly

Each amino acid is represented by a three-letter abbreviation.

Lys = lysine His = histidine Gly = glycine

Glycine has the structure H₂NCH₂COOH

D₂O is used as the solvent when obtaining a¹H NMR spectrum for lysine.

Give one reason why D₂O is used rather than CCl₄ and one reason why D₂O is used rather than water.

D₂O rather than water

GHK is commonly used in cosmetics as part of anti-ageing treatments.

GHK binds to copper(II) ions in the body to form GHK–Cu

Figure 6 shows the structure of GHK–Cu

Use Figure 6 to determine the structure of the amino acid histidine, His

Lysine molecules can polymerise to give poly(lysine).

Increasing the temperature of an alkaline solution of poly(lysine) changes the type of secondary structure in poly(lysine), as shown.

Name the type of secondary structure before and after heating.

Type of secondary structure before heating

Type of secondary structure after heating

This question is about spectroscopy.

Compound P is a hydrocarbon with only one peak (a singlet) in its¹H NMR spectrum.

Carbon has a precise A_r of 12.00000

Hydrogen has a precise A_r of 1.00783

Use this information to deduce the molecular formula of P. Show your working.

Suggest two possible structures for P.

Explain how P can be identified using its infrared spectrum above 1500 cm^–1

Use Table A in the Data Booklet to help you to answer this question.

Molecular formula

Structure 1

Structure 2

Compound Q has the molecular formula C₅H₈O₂

Figure 7 shows the¹³C NMR spectrum of compound Q.

Figure 8 shows the¹H NMR spectrum of compound Q.

Explain what you can deduce about the structure of compound Q.

In your answer you should refer to

• the peaks in the¹³C NMR spectrum

• the chemical shift values for the peaks in the¹H NMR spectrum

• the splitting pattern for the peaks in the¹H NMR spectrum.

Give the structure of compound Q.

The answer space for this question continues on the next page

This question is about gas volumes.

Figure 9 shows some of the apparatus needed to determine an experimental value for the M_r of an unknown volatile liquid Y.

A student uses this method to determine an experimental value for the M_r of Y.

1. Record the volume of air in a gas syringe.

2. Collect a sample of Y in a hypodermic syringe.

3. Record the mass of the hypodermic syringe and Y.

4. Push the needle of the hypodermic syringe through the rubber cap on the gas syringe.

5. Inject a small amount of Y into the gas syringe.

6. Remove the hypodermic syringe from the gas syringe.

7. Record the mass of the hypodermic syringe and the remaining Y.

8. Record the volume of gas in the gas syringe.

9. Record the temperature in the oven and the atmospheric pressure.

Use the results to determine an experimental value for the M_r of Y.

The gas constant, R = 8.31 J K^–1 mol^–1

Show your working.

The percentage uncertainty in the volume of Y in the gas syringe is 0.95%

The percentage uncertainty in the temperature is 0.12%

The uncertainty in each balance reading is ± 0.0005 g

Assume that the uncertainty in the value for pressure is negligible.

Calculate the percentage uncertainty in the use of the balance in this experiment.

Use your answer and the percentage uncertainties for volume and temperature to calculate a range of values for the M_r of Y.

(If you were unable to calculate an experimental value for the M_r of Y in Question 08.1, assume it is 141. This is not the correct answer.)

A teacher suggests placing a seal over the needle of the hypodermic syringe after collecting the sample of liquid Y, and then replacing the seal after injecting the liquid into the gas syringe.

Give a reason why the teacher’s suggestion will improve the experiment.

A mixture of methane and propane has a volume of 40 cm³

This mixture needs exactly 170 cm³ of oxygen for complete combustion.

The equations for these reactions are

Calculate the volume

• of methane in the original mixture

• of propane in the original mixture.

All volumes are measured at the same temperature and pressure.

This question is about rates of reaction.

The rate of hydrolysis of a bromoalkane (RBr) is investigated using this method.

• A boiling tube has a cross drawn onto it.

• An aqueous solution of silver nitrate is added to an ethanolic solution of RBr in the boiling tube in a warm water bath.

• The time is recorded for the cross on the boiling tube to become invisible.

The method is repeated at different temperatures.

State why the cross on the boiling tube becomes invisible.

The volume and concentration of each substance used at each temperature is kept constant.

Identify one other variable that should be kept constant to ensure that the investigation is fair.

The reaction between the bromoalkane RBr and an aqueous solution of KOH is investigated.

The rate constant k for this reaction is determined at a series of temperatures T.

The Arrhenius equation can be written in this form.

Table 2 shows an incomplete set of results for this investigation.

Complete Table 2.

The results in Table 2 can be used to plot a graph to determine the activation energy E_a for this reaction.

Complete the x-axis in Figure 10 by adding an appropriate scale.

Plot the graph on the grid in Figure 10.

Use your graph to determine a value, in kJ mol^–1, for the activation energy E_a

The gas constant, R = 8.31 J K^–1 mol^–1

The rate equation for the reaction between a different bromoalkane (R₂CHBr) and an aqueous solution of KOH is

Which of these is a correct mechanism for the reaction between R₂CHBr and KOH?

Tick (✓) one box.

Explain, in terms of bond polarity, why R₂CHBr and KOH react together.