AQA A Level Chemistry Paper 1 June 2025 question paper 7405/1

This question is about some Group 2 elements and their compounds.

Magnesium is reacted with titanium(IV) chloride to extract titanium metal.

Give the equation for this reaction.

State the role of magnesium in this reaction.

Equation

Role of magnesium

Complete Table 1 by giving the formula of a suitable calcium compound for each use.

Magnesium hydroxide is used to relieve the symptoms of indigestion by neutralising stomach acid.

Suggest why magnesium hydroxide is safer than sodium hydroxide as a treatment for indigestion.

An ionic compound of a Group 2 element dissolves in water to form solution X.

Separate samples of solution X are tested to identify the ions.

Table 2 shows the observations.

Identify the Group 2 cation in solution X.

Give an ionic equation for the reaction that occurs in Test 1.

Ionic equation

Identify the anion in solution X.

Give an ionic equation, including state symbols, for the reaction that occurs in Test 2

Explain why AgNO₃(aq) is acidified.

Ionic equation

Give one property of barium sulfate that makes it useful in hospitals.

This question is about ionisation energies.

Explain why beryllium is the element with the highest first ionisation energy in Group 2.

Give an equation, including state symbols, to show the process that occurs when the second ionisation energy of beryllium is measured.

Predict which element in Period 3 has the lowest second ionisation energy.

Figure 1 shows a plot of log₁₀(ionisation energy) for a Period 3 element.

The ionisation energies are measured in kJ mol^–1

Deduce the identity of this element.

Explain your answer.

Use Figure 1 to determine the third ionisation energy, in kJ mol^–1, of this element.

This question is about the chemistry of copper.

Deduce the number of unpaired electrons in a Cu²⁺ ion.

Describe how water acts as a ligand in the formation of [Cu(H₂O)₆]²⁺

A solution of sodium carbonate is added to a blue solution containing

State what is observed.

Give an equation for the reaction.

Equation

When a solution containing [Cu(H₂O)₆]²⁺ ions reacts with an excess of concentrated hydrochloric acid, a ligand exchange reaction occurs.

Blue Yellow

The shape and the colour of the [CuCl₄]^2– ion are different from the shape and the

Explain

• the shape of each complex ion and why these shapes are different

• how colour arises in complex ions

• why the [CuCl₄]^2– ion has a yellow colour, different from the blue colour of the

An excess of water, followed by an excess of concentrated aqueous ammonia, is added to a solution containing [CuCl₄]^2– ions.

State what is observed.

Give an equation for the overall change that occurs.

Equation

A solution contains M₂[Cu(C₂O₄)₂(H₂O)₂] where M is a metal.

A student does a titration to determine the identity of M.

• 2.52 g of solid M₂[Cu(C₂O₄)₂(H₂O)₂] are dissolved in dilute sulfuric acid.

• This solution is transferred to a volumetric flask and made up to 250 cm³ with dilute sulfuric acid.

• A 25.0 cm³ portion is pipetted into a conical flask.

• The mixture in the conical flask is heated to 60 °C and then titrated with 0.0200 mol dm^–3 KMnO₄ solution.

• Several titrations are done and the student’s results are shown in Table 3.

In this titration, only the C₂O₄^2– ions react with the MnO₄^– ions. 2 mol of MnO₄^– ions react with 5 mol of C₂O₄^2– ions.

Give an equation for the reaction between C₂O₄^2– ions and MnO₄^– ions in acidic solution.

Calculate the mean titre from the student’s results.

Calculate the M_r of M₂[Cu(C₂O₄)₂(H₂O)₂]

Identify M.

Draw the structure of two stereoisomers of the complex ion in M₂[Cu(C₂O₄)₂(H₂O)₂] and include the charge on each structure.

Structure 1
Structure 2

Nitrogen dioxide gas is formed when magnesium nitrate is heated.

Table 4 shows some thermodynamic data.

Give the standard conditions indicated by the symbol in Δ_f and

Use the equation and the data in Table 4 to calculate the temperature at which this reaction becomes feasible.

Nitrogen dioxide can also be produced in a reaction between ammonia and oxygen.

Table 5 shows some bond enthalpy values.

Assume that the bonds between N and O in NO₂ are the same.

Calculate the mean bond enthalpy, in kJ mol^–1, for a bond between N and O in NO₂

An alloy of platinum and rhodium is used as a catalyst in the reaction.

What type of catalyst is this?

Some ammonia and oxygen are reacted and the mixture is left to reach equilibrium at a fixed temperature.

Explain why increasing the temperature of this equilibrium mixture decreases the mole fraction of NO₂ in the equilibrium mixture.

This question is about the halogens and some of their compounds.

Explain why chlorine has a lower boiling point than bromine.

Bromine reacts with fluorine to form BrF₃

Determine the oxidation state of bromine and of fluorine in BrF₃

Draw the shape of a BrF₃ molecule.

Include any lone pairs of electrons that influence the shape.

Explain why the BrF₃ molecule has the shape you have drawn.

Shape

Explanation of shape

Solid sodium bromide reacts with concentrated sulfuric acid.

Two reactions occur

• an acid-base reaction

• a redox reaction.

Give an equation and an observation for each reaction.

Equation for acid-base reaction

Observation for acid-base reaction

Equation for redox reaction

Observation for redox reaction

Iodide ions reduce copper(II) ions in aqueous solution to form a precipitate of copper(I) iodide.

Give an equation for this redox reaction.

An alkaline hydrogen-oxygen fuel cell uses hydrogen and oxygen to produce electricity.

The overall equation for the reaction is

Figure 2 represents an alkaline hydrogen-oxygen fuel cell in use to power a motor.

Give a half-equation for the reaction occurring, in alkaline conditions, at each electrode.

At negative electrode

At positive electrode

Suggest why it is not necessary to replace the KOH electrolyte during the operation of this fuel cell.

Describe how the reactions at the electrodes generate an electric current that can power the motor in the external circuit.

This fuel cell uses pure oxygen, rather than air, as an oxidising agent.

Suggest the identity of the gas in air that would react with the KOH and affect the efficient operation of the cell.

When an alkaline hydrogen-oxygen fuel cell is used to power the motor in a car, the hydrogen can be stored as a liquid.

Suggest an advantage of storing hydrogen as a liquid.

Which graph shows the change in EMF, with time, for an alkaline hydrogen-oxygen fuel cell?

Tick (✓) one box.

An acidic hydrogen-oxygen fuel cell has different reactions at the electrodes.

Suggest why the EMF of the acidic hydrogen-oxygen fuel cell is the same as that of the alkaline hydrogen-oxygen fuel cell.

This question is about vanadium and some of its compounds.

State the block in the Periodic Table that contains vanadium.

Suggest why vanadium can be pulled into thin wires.

Vanadium(V) oxide is a catalyst in the Contact process.

Give two equations to show how vanadium(V) oxide acts as a catalyst in this process.

Equation 1

Equation 2

Table 6 shows some electrode half-equations and their standard electrode potentials.

Sn reduces VO₂⁺ in acidic solution.

Use the data in Table 6 to deduce an overall equation for the reaction that occurs.

Vanadium(III) sulfate is a pale yellow solid at room temperature.

Explain why vanadium(III) sulfate has a high melting point.

When vanadium(III) sulfate dissolves in water, the vanadium-containing species formed is acidic.

Give an equation to show how vanadium(III) sulfate dissolves in water to form the acidic vanadium-containing species.

Explain why the vanadium-containing species is acidic.

Equation

Compound Q is found in crude oil and has the molecular formula C₃₃H₃₄N₄VO₄

A sample of Q is ionised by electrospray ionisation in a time of flight (TOF) mass spectrometer. The spectrum produced shows that the

Give an equation to show how Q is ionised using electrospray ionisation.

Determine the m / z value of the molecular ion formed in this ionisation process.

Equation

A sample of vanadium contains only⁴⁹V and⁵¹V

The relative atomic mass of vanadium in this sample is 50.97

Calculate the percentage abundance of⁵¹V in this sample.

This question is about acids and bases.

Nitric acid is a strong acid.

Calculate the pH of 0.150 mol dm^–3 nitric acid.

Give your answer to 2 decimal places.

Propanoic acid is a weak acid.

Calculate the concentration of a solution of propanoic acid with pH = 2.89 at 25 °C

The acid dissociation constant (K_a) for propanoic acid at 25 °C

A student records the pH as an alkali is added to an acid.

Figure 3 shows the pH curve for this reaction.

Which of these combinations gives the pH curve shown in Figure 3 ?

Different indicators change colour across different pH ranges.

Buffer solution B is made by dissolving 0.656 g of sodium ethanoate (M_r = 82.0) in 50 cm³ of 0.120 mol dm^–3 ethanoic acid.

This buffer solution has pH = 4.87

Explain, qualitatively, how this buffer solution resists pH change when a small amount of sodium hydroxide solution is added.

Calculate the pH change that occurs when 1.50 cm³ of 0.200 mol dm^–3 HCl(aq) are added to buffer solution B.

Give your answer to 2 decimal places.

The acid dissociation constant (K_a) for ethanoic acid at 25 °C is 1.78 × 10^–5 mol dm^–3