Reversible reactions and equilibrium: past paper questions

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• Question 17May/June 2026, paper 11Multiple choice1 mark

  Which statement about cobalt(II) chloride and copper(II) sulfate is correct?

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• Question 15Oct/Nov 2025, paper 11Multiple choice1 mark

  Blue hydrated copper(II) sulfate produces a white solid when it is heated. The white solid turns blue when water is added. Which word describes the reaction of hydrated copper(II) sulfate?

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• Question 18Oct/Nov 2024, paper 12Multiple choice1 mark

  When a few drops of water are added to a solid, E, the colour changes from blue to pink. What is E?

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• Question 14Oct/Nov 2023, paper 11Multiple choice1 mark

  Solid S changes colour from white to blue when water is added. What is S?

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• Question 15May/June 2026, paper 12Multiple choice1 mark

  What is shown by the symbol $\rightleftharpoons$ in the equation for a chemical reaction?

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• Question 17Oct/Nov 2025, paper 12Multiple choice1 markHas a diagram

  When pink cobalt(II) chloride is heated, it forms a blue solid and water. When water is added to the blue solid, it releases heat and a pink solid is formed. Which row describes the type of reaction that occurs and the pink cobalt(II) chloride?

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• Question 17Oct/Nov 2024, paper 13Multiple choice1 markHas a diagram

  When blue copper(II) sulfate is heated, a white solid and water are formed. The white solid turns blue and gives out heat when water is added to it. Which terms describe the blue copper(II) sulfate and the reactions?

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• Question 16Oct/Nov 2023, paper 12Multiple choice1 mark

  Which reaction shows a colour change from white to blue?

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• Question 18May/June 2026, paper 13Multiple choice1 mark

  Substance X is a blue solid. When X is heated, steam is produced and the solid turns white. What is X?

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• Question 16Oct/Nov 2025, paper 13Multiple choice1 mark

  Blue copper(II) sulfate crystals are heated in air until they turn into a white powder. The powder is allowed to cool and after a few days it starts to turn blue. Why does the white powder start to turn blue?

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• Question 15Oct/Nov 2024, paper 21Multiple choice1 mark

  Which statements about the Haber process are correct?

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• Question 13Oct/Nov 2023, paper 13Multiple choice1 markHas a diagram

  When water is added to anhydrous iron(III) chloride, ${\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{l}}_3$, hydrated iron(III) chloride, ${\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{l}}_3\cdot 6{\mathrm{H}}_2\mathrm{O}$, is formed and energy is given out.

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• Question 18May/June 2026, paper 21Multiple choice1 mark

  Four statements about the Haber process and the Contact process are listed. 1 Both processes are carried out at $200\text{ kPa}$. 2 Both processes are carried out at $450{}^{\circ }\text{C}$.

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• Question 17Oct/Nov 2025, paper 21Multiple choice1 mark

  Which equation represents one of the reactions in the Contact process?

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• Question 16Oct/Nov 2024, paper 21Multiple choice1 mark

  Which substance is a raw material used to manufacture sulfuric acid?

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• Question 15Oct/Nov 2023, paper 13Multiple choice1 mark

  Anhydrous cobalt(II) chloride is blue and turns pink when water is added. How is this reaction reversed?

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• Question 17May/June 2026, paper 22Multiple choice1 mark

  The Haber process is used to make ammonia. The equation for the reaction is shown. $${\text{N}}_2+3{\text{H}}_2\rightleftharpoons 2{\text{NH}}_3$$ Which statements about the Haber process are correct?

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• Question 19Oct/Nov 2025, paper 21Multiple choice1 markHas a diagram

  In the Haber process, nitrogen and hydrogen react to form ammonia. $${\mathrm{N}}_2+3{\mathrm{H}}_2\rightleftharpoons 2\mathrm{N}{\mathrm{H}}_3$$ The forward reaction is exothermic. Which changes in pressure and temperature increase the yield of ammonia?

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• Question 16Oct/Nov 2024, paper 22Multiple choice1 mark

  Hydrogen gas reacts with iodine gas to form hydrogen iodide gas in an equilibrium reaction.

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• Question 15Oct/Nov 2023, paper 21Multiple choice1 markHas a diagram

  Sulfuric acid is produced by the Contact process. Which row shows the typical conditions used in the process?

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• Question 19May/June 2026, paper 23Multiple choice1 mark

  The equation for one of the reactions in the Contact process is shown. $$2{\text{SO}}_2\text{(g)}+{\text{O}}_2\text{(g)}\rightleftharpoons 2{\text{SO}}_3\text{(g)}\mathrm{\Delta }H=-196\text{ kJ / mol}$$ Which statement about this reaction is correct?

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• Question 17Oct/Nov 2025, paper 22Multiple choice1 mark

  Which statement about the conditions used in the Haber process and in the Contact process is correct?

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• Question 17Oct/Nov 2024, paper 23Multiple choice1 mark

  In the Haber process, an equilibrium is established. $${\text{N}}_2\text{(g)}+3{\text{H}}_2\text{(g)}\rightleftharpoons 2{\text{NH}}_3\text{(g)}$$ The forward reaction is exothermic. Which change to the reaction conditions will move the position of equilibrium to the left?

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• Question 16Oct/Nov 2023, paper 22Multiple choice1 markHas a diagram

  The decomposition of dinitrogen tetroxide, ${\mathrm{N}}_2{\mathrm{O}}_4$, into nitrogen dioxide, ${\mathrm{N}\mathrm{O}}_2$, is a reversible reaction. The equation for the reaction is shown.

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• Question 6May/June 2026, paper 41Structured16 marks

  This question is about metallic compounds. Zinc oxide, $\text{ZnO}$, reacts with both acids and alkalis to produce salts. State the term given to oxides that react with both acids and alkalis.

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• Question 18Oct/Nov 2025, paper 22Multiple choice1 mark

  The equation shows the equilibrium between dinitrogen tetroxide, ${\text{N}}_2{\text{O}}_4$, and nitrogen dioxide, ${\text{NO}}_2$. The colours of the reactant and product are shown.

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• Question 4May/June 2026, paper 42Structured13 marks

  Chromium, copper and nickel are transition elements. State two physical properties of transition elements that are different from Group I metals.

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• Question 19Oct/Nov 2025, paper 23Multiple choice1 markHas a diagram

  Ethanol is manufactured by the addition of steam to ethene. $${\text{C}}_2{\text{H}}_4(\text{g})+{\text{H}}_2\text{O}(\text{g})\rightleftharpoons {\text{C}}_2{\text{H}}_5\text{OH}(\text{g})$$ The reaction conditions are ${300}^{\circ }\text{C}$ and $60\text{ atm}$.

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• Question 5Oct/Nov 2024, paper 43Structured15 marksHas a diagram

  This question is about rate of reaction and equilibrium. A student investigates the rate of decomposition of aqueous hydrogen peroxide, ${\mathrm{H}}_2{\mathrm{O}}_2$, using manganese(IV) oxide as a catalyst. The equation for the reaction is shown.

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• Question 6May/June 2026, paper 43Structured14 marks

  This question is about oxides. Aluminium oxide, $\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$, is an amphoteric oxide. State the meaning of the term amphoteric.

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