A-level Chemistry extended-response trainer

AQA 7405

ORIGINAL

Original AQA A-level Chemistry extended-response practice across physical, inorganic and organic chemistry — Maxwell-Boltzmann and catalysts, Kp and Le Chatelier, electrode potentials, buffers, entropy and feasibility, Period 3 oxides, transition-metal colour and catalysis, aqueous ion reactions, aromatic substitution, polymer disposal, spectroscopic structure determination and multi-step synthesis. Plan the answer, self-mark against the level descriptors, then read a model response.

Board and spec code confirmed against AQA 7405 · registry checked 2026-07-11How this checking works

How to use it: write your full answer first, then reveal the mark scheme and tick the points you made. AQA marks these by level — a detailed, linked answer — not by counting points, so the tick count is only a rough guide. Read the model answer to see what a Level 3 looks like.

Physical — kinetics and the Maxwell-Boltzmann distribution

Explain

A gas-phase reaction has a high activation energy. Explain, using the Maxwell-Boltzmann distribution of molecular energies, why a small rise in temperature produces a large increase in the rate of this reaction, and why adding a catalyst also increases the rate.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Physical — equilibria, Kp and industrial conditions

Explain

Ammonia is manufactured by the reversible reaction N₂(g) + 3H₂(g) <=> 2NH₃(g), for which the enthalpy change of the forward reaction is -92 kJ mol⁻¹. A typical plant operates at about 450 °C and 200 atm with an iron catalyst. Explain how temperature, total pressure and the catalyst each affect the equilibrium yield of ammonia and the value of Kp, and justify the conditions chosen.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Physical — electrode potentials and electrochemical cells

Describe and explain

A student builds a cell from a Zn²⁺/Zn half-cell and a Cu²⁺/Cu half-cell under standard conditions. The standard electrode potentials are E(Zn²⁺/Zn) = -0.76 V and E(Cu²⁺/Cu) = +0.34 V. Describe how the cell is assembled and measured, explain which electrode is negative and calculate the emf, and evaluate one advantage and one drawback of a hydrogen-oxygen fuel cell compared with a petrol engine.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Physical — acids, bases and buffer action

Explain

A buffer solution is prepared by dissolving sodium ethanoate in aqueous ethanoic acid. Explain how this solution resists a change in pH when a small amount of a strong acid is added and when a small amount of a strong alkali is added, and explain how its pH can be calculated from Ka.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Physical — entropy and Gibbs free-energy change

Explain

Solid ammonium chloride decomposes on heating: NH₄Cl(s) → NH₃(g) + HCl(g). For this reaction the enthalpy change is +176 kJ mol⁻¹ and the entropy change is +285 J K⁻¹ mol⁻¹. Explain what these two values tell you about the reaction, and explain, with a calculation, why the reaction becomes feasible only above a particular temperature.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Inorganic — Period 3 elements and their oxides

Describe and explain

Separate samples of sodium oxide, magnesium oxide, silicon dioxide and sulfur dioxide are each added to water. Describe what happens in each case and the approximate pH of the mixture produced, and explain the differences in terms of the bonding and structure of the oxides.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Inorganic — transition metals: colour and catalysis

Explain

Explain why aqueous solutions of most transition metal ions are coloured while solutions containing Sc³⁺ or Zn²⁺ are colourless, and explain, with an example of each, how transition metals are able to act as heterogeneous and as homogeneous catalysts.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Inorganic — reactions of ions in aqueous solution

Describe and explain

Separate aqueous solutions containing [Fe(H₂O)₆]²⁺, [Fe(H₂O)₆]³⁺ and [Al(H₂O)₆]³⁺ are each treated with aqueous sodium hydroxide, added until in excess, and then with aqueous sodium carbonate. Describe what would be observed in each case and explain why the 3+ ions are more acidic than the 2+ ion.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Inorganic — ligand substitution and the shapes of complex ions

Describe and explain

Aqueous copper(II) sulfate contains the [Cu(H₂O)₆]²⁺ ion. Describe and explain what is observed when an excess of concentrated aqueous ammonia is added to it, and separately when an excess of concentrated hydrochloric acid is added, referring to the colour, coordination number and shape of each complex formed.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Q10

Organic — aromatic chemistry and electrophilic substitution

Explain

Explain, in terms of its bonding, why benzene reacts by electrophilic substitution rather than by electrophilic addition, and describe how the electrophile is generated and used in the nitration of benzene.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Q11

Organic — addition and condensation polymers and their disposal

Compare and explain

Poly(propene) is made from propene, and a polyester is made from benzene-1,4-dicarboxylic acid and ethane-1,2-diol. Compare how the two polymers are formed and explain why the polyester can be broken down by hydrolysis and is more readily biodegradable, while poly(propene) is not.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Q12

Organic — structure determination by spectroscopy

Deduce and explain

A colourless liquid X has the molecular formula C₃H₆O₂. Its mass spectrum shows a molecular ion peak at m/z = 74. Its infrared spectrum has a broad absorption between 2500 and 3000 cm⁻¹ and a strong absorption at 1710 cm⁻¹. Its proton NMR spectrum shows three peaks with an integration ratio of 3 : 2 : 1, one of them at about 11.5 ppm. X effervesces when aqueous sodium carbonate is added to it. Deduce the structure of X and explain how each piece of evidence supports your deduction.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Q13

Organic — multi-step synthesis and reaction pathways

Devise and explain

Devise a synthesis of propan-1-amine, CH₃CH₂CH₂NH₂, starting from ethene. Give the reagents and conditions for each step and identify the type of reaction in each, and explain why the conditions chosen for one of the steps must be specified particularly carefully.

[6 marks]

Total for this question: 6

Write your full answer first — then mark it.

Extended responses are where the grades are

Send me your answer to one of these and I'll mark it like the examiner would. Free intro call, then a free first lesson.

Book a free intro call

Stuck on six-mark answers?