AQA A Level Chemistry Paper 3 June 2024 question paper 7405/3

The structure of 2-hydroxybenzenecarboxylic acid is shown.

Give the equation for the reaction of 2-hydroxybenzenecarboxylic acid with methanol.

In your equation, include the skeletal formula of the organic product.

Aspirin is produced from 2-hydroxybenzenecarboxylic acid by reaction with ethanoic anhydride in the presence of concentrated phosphoric acid.

Method

1. Add 2-hydroxybenzenecarboxylic acid to a conical flask.

2. Add excess ethanoic anhydride.

3. Add a few drops of concentrated phosphoric acid.

4. Heat the flask to 85 °C for 10 minutes.

5. Cool the flask and pour the contents into 150 cm³ of cold water.

6. Filter and wash the impure solid aspirin.

7. Recrystallise the aspirin using a 50:50 mixture of water and ethanol.

8. Check the purity of the aspirin.

Aspirin can also be produced by reacting 2-hydroxybenzenecarboxylic acid with ethanoyl chloride.

State why ethanoic anhydride is preferred to ethanoyl chloride for this preparation.

Give the name of the mechanism for the reaction of 2-hydroxybenzenecarboxylic acid with ethanoic anhydride.

Suggest the role of the concentrated phosphoric acid.

Suggest why reflux is not essential when the flask is heated to 85 °C for 10 minutes.

Complete and label the diagram to show how the impure solid is filtered.

Suggest the identity of two impurities present in the filtered solid aspirin before it is washed in Step 6 of the method.

Describe the recrystallisation process used to purify the aspirin.

Include the method and apparatus used.

State the physical property that is measured to check the purity of the aspirin.

Describe two ways the result would show that the product is impure.

Physical property

The rate of reaction between calcium carbonate and hydrochloric acid is investigated using a continuous monitoring method.

Method

• Place a conical flask on a balance and add approximately 20 g of large marble chips.

• Add 50 cm³ of 0.4 mol dm^–3 hydrochloric acid.

• Place a loose cotton wool plug in the neck of the flask.

• Zero the mass reading on the balance.

• Start a timer.

• Record the loss in mass (m_t) every 30 seconds for 4 minutes.

• Wait for the reaction to finish and record the total mass loss (m_total).

• Plot a graph of (m_total – m_t) against time.

Figure 1 shows a graph of the results obtained during the first 240 s

Suggest why a loose cotton wool plug is placed in the neck of the flask, instead of leaving the flask open or inserting a bung.

Instead of leaving the flask open

Instead of inserting a bung

The mass of carbon dioxide produced in time t is equal to m_t.

The total mass of CO₂ produced during the reaction is equal to m_total.

Explain why (m_total – m_t) is proportional to the concentration of hydrochloric acid remaining in the flask at time t.

Table 1 shows the rate of reaction, calculated from the gradient of the curve, at five different times.

(m_total – m_t) is proportional to the concentration of unreacted HCl at time t.

On the grid in Figure 2 plot the rate of reaction (y-axis) against (m_total – m_t) (x-axis).

State how the graph in Figure 2 confirms that the rate equation for this reaction is

Rate = k [HC l ]

In this experiment the variable measured is mass loss.

The rate of this reaction at a constant temperature can be investigated in other ways.

Suggest two other variables that can be measured instead of mass loss.

The thermal decomposition of but-3-en-1-ol is investigated at different temperatures (T).

CH₂=CHCH₂CH₂OH → CH₂=CHCH₃ + HCHO

The results from the investigation are used to calculate the rate constant, k, at each temperature.

Table 2 shows some of the results.

Complete Table 2 with the missing values at 573 K

The overall order of the reaction can be deduced from a piece of information in one of the column headings in Table 2.

Identify this piece of information and deduce the overall order.

Piece of information

The Arrhenius equation can be written in the form shown.

On the grid in Figure 3 plot a graph of ln k against

Use your graph from Question 03.3 to calculate a value for E_a, in kJ mol^–1, for the thermal decomposition of but-3-en-1-ol.

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

2-Methylpent-4-en-2-ol decomposes in a similar way to but-3-en-1-ol, to produce an alkene and a carbonyl compound.

Deduce the structures of the alkene and the carbonyl compound.

alkene
carbonyl compound

Figure 4 shows how the pH changes as 0.100 mol dm^–3 sodium hydroxide solution is added to 25.0 cm³ of 0.0800 mol dm^–3 aqueous propanoic acid at 298 K

Propanoic acid is a weak acid.

State the meaning of weak in this context.

Suggest why a student doing an experiment to produce the curve in Figure 4 would add the sodium hydroxide solution dropwise around the equivalence point.

Give an expression for K_a for propanoic acid (CH₃CH₂COOH).

Use this expression to show that pH = pK_a when half of the propanoic acid has reacted with sodium hydroxide.

Use the pH from Figure 4, when half of the propanoic acid has reacted, to calculate

When sodium hydroxide solution is added to aqueous propanoic acid, the solution formed acts as a buffer when between 5 cm³ and 15 cm³ have been added.

Explain why the pH stays approximately constant during this part of the experiment.

Methyl orange and universal indicator are not suitable indicators for the titration of solutions of propanoic acid with sodium hydroxide.

State the reason why each indicator is not suitable.

Universal indicator

Some complexes containing transition metal ions are coloured.

• Explain why some complexes containing transition metal ions are coloured.

• List the factors that affect the colour.

• Describe how colorimetry can be used to determine the concentration of a coloured complex.

Figure 5 shows the visible spectrum of [Cu(H₂O)₆]²⁺

Use the wavelength at the peak of the curve in Figure 5 to calculate the change in energy, in J, of an electron when it absorbs radiation with this wavelength.

Which row contains two species with different numbers of electrons?

Which element has the highest third ionisation energy?

What is the formula of ammonium ethanedioate?

Which diagram shows the formation of a dative covalent bond?

Which substance does not have any bond angles of 120°?

Which molecule does not have a permanent dipole?

Which compound forms the greatest number of hydrogen bonds per molecule in the liquid state?

The Maxwell–Boltzmann distribution curve is shown for a gaseous reaction mixture.

What is represented by the total area under the curve?

A student investigated the reaction between magnesium and hydrochloric acid.

The results are plotted on this graph.

Which value is closest to the rate of reaction, in cm³ s^–1, at 70 s?

Which statement explains why the rate of a reaction increases when a catalyst is added at a constant temperature?

A cell with EMF = +2.15 V is made from two electrodes.

The half-equations for the two electrodes are shown.

positive electrode:

PbO₂(s) + 3 H⁺(aq) + HSO₄^–(aq) + 2 e^– PbSO₄(s) + 2 H₂O(l)

negative electrode:

What is the standard electrode potential of the PbO₂ / PbSO₄ electrode?

Values of the ionic product of water (K_w) at different temperatures are given.

Which statement is correct?

Consider the Period 3 elements from sodium to chlorine.

Which statement is correct?

Which statement correctly describes a trend down Group 7 from C l to I ?

X represents C l, Br or I

Which statement about chloride ions is correct?

Aqueous aluminium sulfate is added to aqueous sodium carbonate.

What are the formulas of the precipitate and the gas formed?

What is the correct structural formula for 4-chloro-2-methylpent-2-enoic acid?

In which conversion does a nucleophile attack the organic reactant?

Compound Y has the structural formula CH₃COOCH₂CH(CH₃)₂

Which compound is a position isomer of Y ?

Which compound shows E – Z isomerism?

What is the product when 3-methylbutan-2-one reacts with acidified KCN?

Which statement concerning nylon-6,6 is correct?

Which statement about the industrial production of ethanol from ethene at 300 °C is correct?

Which compound is formed by the acid hydrolysis of phenyl benzenecarboxylate?

Which type of polymer is most difficult to hydrolyse?

In which polymer does hydrogen bonding occur between the polymer chains?

Which structure shows a zwitterion of an amino acid?

The diagram shows a gas chromatogram for a sample containing four isomers with

The carrier gas is nitrogen and the stationary phase is polar.

Which of the four isomers in this sample is the most abundant?

Which structure is formed by phenylalanine in solution at pH = 3?