Reaction kinetics: past paper questions

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• Question 14May/June 2026, paper 11Multiple choice1 mark

  Nitrogen and hydrogen react to form ammonia in a reversible reaction. $${\text{N}}_2+3{\text{H}}_2\rightleftharpoons 2{\text{NH}}_3\mathrm{\Delta }H=-92{\text{ kJ mol}}^{-1}$$

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• Question 14Oct/Nov 2025, paper 11Multiple choice1 mark

  Photochromic glass, used for sunglasses, darkens when exposed to bright light and becomes more transparent again when the light is less bright. The darkness of the glass is due to the presence of silver atoms. The following reactions are involved.

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• Question 14Oct/Nov 2024, paper 11Multiple choice1 markHas a diagram

  In acidic conditions, iodine reacts with propanone in a substitution reaction.

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• Question 14Oct/Nov 2023, paper 11Multiple choice1 markHas a diagram

  In reaction 1, a student measures the initial rate of production of ${\mathrm{C}\mathrm{O}}_2(\mathrm{g})$ when ${\mathrm{C}\mathrm{u}\mathrm{C}\mathrm{O}}_3(\mathrm{s})$ is added to $50{\text{ cm}}^3$ of $0.1{\text{ mol dm}}^{-3}{\mathrm{H}\mathrm{N}\mathrm{O}}_3(\mathrm{a}\mathrm{q})$.

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• Question 15May/June 2026, paper 11Multiple choice1 markHas a diagram

  The diagram shows the Boltzmann distribution of energies in one mole of a gas. The gas takes part in a reaction with an activation energy, $E_{\text{a}}$. Which statement correctly describes the effect of an increase in temperature?

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

  The reversible reaction between methanol and ethanoic acid liquids is catalysed by adding a small volume of concentrated sulfuric acid. Two statements about this reaction are listed. 1 The sulfuric acid is a homogeneous catalyst.

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• Question 15Oct/Nov 2024, paper 11Multiple choice1 markHas a diagram

  The diagram shows a Boltzmann distribution curve. The axes are not labelled. Points X and Y are points on the vertical axis.

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• Question 15Oct/Nov 2023, paper 11Multiple choice1 mark

  The forward reaction of a reversible reaction is exothermic and has an activation energy of $+30{\text{ kJ mol}}^{-1}$. The reverse reaction proceeds by a mechanism that is the exact reverse of the mechanism of the forward reaction.

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• Question 15May/June 2026, paper 12Multiple choice1 markHas a diagram

  The diagram shows a Boltzmann distribution of molecular energies for a gaseous mixture. The distribution has a peak, labelled P. What happens when an effective catalyst is added to the mixture?

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• Question 13Oct/Nov 2025, paper 12Multiple choice1 mark

  In the Contact process, sulfur dioxide and oxygen react to form sulfur trioxide. In the Haber process, nitrogen and hydrogen react to form ammonia. Which statement about these processes is correct?

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• Question 15Oct/Nov 2024, paper 12Multiple choice1 mark

  Why does the rate of a gaseous reaction increase when the pressure is increased at a constant temperature?

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• Question 16Oct/Nov 2023, paper 12Multiple choice1 markHas a diagram

  The decomposition of hydrogen peroxide in the presence of ${\text{MnO}}_2$ produces water and oxygen gas.

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• Question 18May/June 2026, paper 12Multiple choice1 mark

  Two procedures are described. 1 Sulfur is burned in an excess of oxygen then NO is added to the product mixture. 2 Sulfur is burned in an excess of oxygen then ${\text{NO}}_2$ is added to the product mixture.

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• Question 14Oct/Nov 2025, paper 12Multiple choice1 mark

  $20.0{\text{ cm}}^3$ of hydrogen peroxide decomposes to water and oxygen in the presence of a suitable catalyst. $160{\text{ cm}}^3$ of oxygen, measured at room conditions, is produced in $5.00\text{ minutes}$.

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• Question 16Oct/Nov 2024, paper 12Multiple choice1 markHas a diagram

  The Boltzmann distribution for a mixture of gases capable of reaction is shown. The two curves represent the mixture of gases at ${25}^{\circ }\text{C}$ and at ${35}^{\circ }\text{C}$. The activation energies for the catalysed and uncatalysed reactions are shown.

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

  The diagram shows a gas syringe with a free-moving piston. The syringe contains gaseous hydrogen, gaseous iodine and gaseous hydrogen iodide at equilibrium. $${\text{H}}_2(\text{g})+{\text{I}}_2(\text{g})\rightleftharpoons 2\text{HI}(\text{g})$$ Three changes are listed.

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• Question 14May/June 2026, paper 13Multiple choice1 markHas a diagram

  The reaction pathway diagram shows the reaction which occurs when $({\text{CH}}_3{)}_3\text{CCl}$ reacts with ${\text{OH}}^{-}$. Which statements are correct?

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• Question 15Oct/Nov 2025, paper 12Multiple choice1 markHas a diagram

  Which reaction pathway diagram shows an endothermic reaction that occurs in two steps and in which the second step of the reaction is likely to be faster than the first?

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• Question 15May/June 2026, paper 13Multiple choice1 markHas a diagram

  The graph shows a Boltzmann distribution for a sample of reacting gas at a temperature $T\text{ K}$. The activation energy, $E_{\text{A}}$, for the reaction is marked. Point Q is the point of intercept of the curve with the value of the activation energy, $E_{\text{A}}$.

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• Question 15Oct/Nov 2024, paper 13Multiple choice1 markHas a diagram

  The diagram shows a Boltzmann distribution curve. The axes are not labelled. [Diagram: Boltzmann distribution curve with point Y at the peak and point X at energy $E_{\mathrm{A}}$] Points X and Y are points on the vertical axis.

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• Question 3May/June 2026, paper 23Structured13 marksHas a diagram

  The conditions used for the conversion of sulfur dioxide to sulfur trioxide in the Contact process are carefully controlled.

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• Question 10May/June 2024, paper 11Multiple choice1 markHas a diagram

  For a certain endothermic reaction, the activation energy is numerically equal to twice the enthalpy change of reaction. Which reaction pathway diagram is correct for this reaction?

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• Question 11May/June 2023, paper 11Multiple choice1 mark

  Iodine and propanone react according to the following equation. $${\mathrm{I}}_2(\mathrm{a}\mathrm{q})+\mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{C}{\mathrm{H}}_3(\mathrm{a}\mathrm{q})\to \mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{C}{\mathrm{H}}_2\mathrm{I}(\mathrm{a}\mathrm{q})+\mathrm{H}\mathrm{I}(\mathrm{a}\mathrm{q})$$ If the concentration of propanone is increased, keeping the total reaction volume constant, the initial rate of the reaction also increases.

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• Question 2May/June 2025, paper 11Multiple choice1 markHas a diagram

  The rate of the reaction between a reactive metal and an excess of a dilute acid is investigated. The total volume of hydrogen gas produced is recorded every 30 seconds for 3 minutes.

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• Question 15May/June 2024, paper 11Multiple choice1 markHas a diagram

  The Boltzmann distribution for the hydrogenation of an alkene at a particular temperature in the absence of a catalyst is shown. Which row correctly describes the effects of adding a nickel catalyst to the reaction vessel?

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• Question 15May/June 2023, paper 11Multiple choice1 mark

  The temperature of a sample of an inert gas is increased. What effect does this have on the number of molecules with the most probable energy and on the number of molecules with higher energy?

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• Question 3May/June 2025, paper 11Multiple choice1 markHas a diagram

  In the diagram, curve X was obtained by measuring the volume of oxygen produced during the decomposition of $100{\text{ cm}}^3$ of $1.0\text{ mol}{\text{dm}}^{-3}$ hydrogen peroxide. A catalyst of manganese(IV) oxide was used.

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• Question 23May/June 2024, paper 11Multiple choice1 mark

  Nitrogen dioxide is a gas that contributes to air pollution. It is produced in internal combustion engines. Which statement is correct?

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• Question 15May/June 2023, paper 12Multiple choice1 mark

  The equations for two reactions are shown. $$\text{reaction X}2\text{NOBr}\to 2\text{NO}+{\text{Br}}_2$$ $$\text{reaction Y}2\text{NOCl}\to 2\text{NO}+{\text{Cl}}_2$$ The two reactions have similar reaction mechanisms.

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• Question 33May/June 2025, paper 11Multiple choice1 markHas a diagram

  A possible mechanism for the exothermic hydrolysis of 2-chloro-2-methylpropane is shown.

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