Reversible reactions and equilibrium: past paper questions

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• Question 16May/June 2026, paper 11Multiple choice1 mark

  When bismuth(III) chloride, ${\text{BiCl}}_3$, is added to water, a reaction occurs and a white precipitate of $\text{BiOCl}$ is formed.

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• Question 16Oct/Nov 2025, paper 11Multiple choice1 mark

  The equation shows the reversible reaction between nitrogen and hydrogen to form ammonia. $${\mathrm{N}}_2+3{\mathrm{H}}_2\rightleftharpoons 2{\mathrm{N}\mathrm{H}}_3$$ The forward reaction is exothermic. Which statement is correct when the temperature is increased?

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• Question 16Oct/Nov 2024, paper 11Multiple choice1 mark

  If calcium carbonate is heated in a closed container, it will decompose, forming calcium oxide and carbon dioxide. Calcium oxide and carbon dioxide can recombine to form calcium carbonate.

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• Question 18Oct/Nov 2023, paper 11Multiple choice1 markHas a diagram

  Aqueous bromine is an equilibrium mixture. $$\mathrm{B}{\mathrm{r}}_2(\mathrm{a}\mathrm{q})+{\mathrm{H}}_2\mathrm{O}(\mathrm{l})\rightleftharpoons \mathrm{O}\mathrm{B}{\mathrm{r}}^{-}(\mathrm{a}\mathrm{q})+\mathrm{B}{\mathrm{r}}^{-}(\mathrm{a}\mathrm{q})+2{\mathrm{H}}^{+}(\mathrm{a}\mathrm{q})$$ Aqueous bromine is orange in colour. The species on the right-hand side of the equation are colourless.

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

  The Haber process is used to make ammonia. Which catalyst is used in the Haber process?

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• Question 17Oct/Nov 2025, paper 12Multiple choice1 mark

  Which statements about the Haber process for the manufacture of ammonia are correct?

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• Question 17Oct/Nov 2024, paper 11Multiple choice1 markHas a diagram

  Which set of conditions is used in the Contact process?

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• Question 17Oct/Nov 2023, paper 12Multiple choice1 markHas a diagram

  Hydrogen is used as a reactant both in the Haber process and in its addition to alkenes. Which row is correct?

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

  Elements X and Y react together in a reversible reaction to form ${\text{XY}}_2$. $$\text{X}+2\text{Y}\rightleftharpoons {\text{XY}}_2$$ $1.0\text{ mol}$ of X is mixed with $1.0\text{ mol}$ of Y and the mixture is left to react until an equilibrium position is reached.

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• Question 7Oct/Nov 2025, paper 21Structured13 marksHas a diagram

  Ethene is used to make ethanol and poly(ethene). Fig. 7.1 shows the displayed formula of ethene. Alkenes such as ethene are manufactured from hydrocarbons such as ${\mathrm{C}}_{12}{\mathrm{H}}_{26}$.

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• Question 22Oct/Nov 2024, paper 11Multiple choice1 markHas a diagram

  When heated, copper(II) sulfate crystals, ${\text{CuSO}}_4\cdot 5{\text{H}}_2\text{O}$, react as shown. $${\text{CuSO}}_4\cdot 5{\text{H}}_2\text{O}(\text{s})\to {\text{CuSO}}_4(\text{s})+5{\text{H}}_2\text{O}(\text{g})$$ When ......1...... copper(II) sulfate, which is ......2......

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• Question 8Oct/Nov 2023, paper 21Structured7 marks

  Ethanoic acid is manufactured from methanol. $${\mathrm{C}\mathrm{H}}_3\mathrm{O}\mathrm{H}(\mathrm{g})+\mathrm{C}\mathrm{O}(\mathrm{g})\rightleftharpoons {\mathrm{C}\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}(\mathrm{g})$$ The forward reaction is exothermic.

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• Question 5Oct/Nov 2025, paper 22Structured11 marks

  Nickel is a transition element. One of the properties of nickel is that it is a catalyst. State a reaction that uses nickel as a catalyst.

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

  Samples of nitrogen and hydrogen are reacted and allowed to reach equilibrium. The equation is shown. $${\text{N}}_2+3{\text{H}}_2\rightleftharpoons 2{\text{NH}}_3\mathrm{\Delta }H=-92\text{ kJ / mol}$$ The temperature is increased and a new equilibrium is established.

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• Question 8Oct/Nov 2023, paper 22Structured7 marks

  The equation for the reaction of carbon monoxide with hydrogen at a high temperature in a closed container is shown. $$\mathrm{C}\mathrm{O}(\mathrm{g})+2{\mathrm{H}}_2(\mathrm{g})\rightleftharpoons {\mathrm{C}\mathrm{H}}_3\mathrm{O}\mathrm{H}(\mathrm{g})$$ methanol The forward reaction is exothermic.

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• Question 18May/June 2025, paper 11Multiple choice1 mark

  In a closed flask, gases Q and R reach a dynamic equilibrium. $$\mathrm{Q}(\mathrm{g})\rightleftharpoons 2\mathrm{R}(\mathrm{g})\mathrm{\Delta }H\text{ is positive}$$ Which change will move the equilibrium to the right?

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• Question 19Oct/Nov 2024, paper 12Multiple choice1 markHas a diagram

  In the diagram, R represents one of the reactions in the Contact process. Which statement is correct?

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• Question 15May/June 2023, paper 11Multiple choice1 markHas a diagram

  The equation for a reaction in the Contact process is shown.

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• Question 19May/June 2025, paper 11Multiple choice1 markHas a diagram

  Which row shows the typical conditions used for the conversion of sulfur dioxide to sulfur trioxide in the Contact process?

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• Question 2Oct/Nov 2024, paper 21Structured15 marksHas a diagram

  Iron is extracted in a blast furnace by the reduction of iron(III) oxide with carbon monoxide. $${\text{Fe}}_2{\text{O}}_3+3\text{CO}\to 2\text{Fe}+3{\text{CO}}_2$$ This reaction is a redox reaction. State the meaning of the term redox reaction.

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• Question 16May/June 2023, paper 11Multiple choice1 markHas a diagram

  Universal indicator contains several dyes. The reversible reaction of one dye, $\text{IndOH}$, is shown.

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• Question 20May/June 2025, paper 11Multiple choice1 markHas a diagram

  The pH of dilute ethanoic acid is measured. The equation for the partial dissociation of ethanoic acid is shown.

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• Question 2Oct/Nov 2024, paper 22Structured14 marks

  Iron is extracted in the blast furnace by the reduction of iron(III) oxide, ${\mathrm{F}\mathrm{e}}_2{\mathrm{O}}_3$. This process is made up of three steps. In step 1, carbon burns in air to produce carbon dioxide.

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• Question 17May/June 2023, paper 12Multiple choice1 mark

  Hydrogen is made industrially by the reaction shown.

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• Question 19May/June 2025, paper 12Multiple choice1 markHas a diagram

  Which row gives the catalyst for each of the two processes?

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• Question 19May/June 2024, paper 11Multiple choice1 mark

  $157.75\text{ g}$ of bismuth(III) chloride, ${\mathrm{B}\mathrm{i}\mathrm{C}\mathrm{l}}_3$, is used to make $500{\text{ cm}}^3$ of solution using distilled water. The aqueous bismuth(III) chloride slowly becomes cloudy as it reacts with water to form insoluble $\mathrm{B}\mathrm{i}\mathrm{O}\mathrm{C}\mathrm{l}$. The reaction is reversible.

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• Question 5May/June 2023, paper 21Structured10 marks

  Ammonium chloride decomposes when heated to make hydrogen chloride and ammonia. This reaction is reversible. The forward reaction absorbs thermal energy.

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• Question 6May/June 2025, paper 21Structured16 marks

  Chlorine, ${\mathrm{C}\mathrm{l}}_2$, is in Group VII of the Periodic Table. The melting point of chlorine is $-101{}^{\circ }\mathrm{C}$ and the boiling point is $-35{}^{\circ }\mathrm{C}$. Explain why chlorine is a liquid at $-50{}^{\circ }\mathrm{C}$.

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• Question 18May/June 2024, paper 12Multiple choice1 mark

  The reaction between calcium oxide and carbon dioxide is reversible and the forward reaction is exothermic. $$\mathrm{C}\mathrm{a}\mathrm{O}(\mathrm{s})+{\mathrm{C}\mathrm{O}}_2(\mathrm{g})\rightleftharpoons {\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3(\mathrm{s})$$

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• Question 5May/June 2023, paper 22Structured9 marks

  Carbon reacts with steam to make carbon monoxide and hydrogen. This reaction is reversible. The forward reaction absorbs thermal energy.

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