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CAIE A Level Chemistry 9701

Reaction kinetics questions

Exam-style questions on Reaction kinetics, ordered from foundation to challenge. Pick one, write your answer the way you would in the exam, and it comes back marked against the mark scheme, point by point.

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Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.

  1. Compare5 marksStandardA student investigates the reaction between aqueous hydrogen peroxide and acidified aqueous potassium iodide, which produces iodine. In Experiment 1, 25 cm3 of 0.050 mol dm^-3 hydrogen peroxide is mixed with 10 cm3 of…
  2. Compare5 marksStandardThe activation energy, EA, of a reaction is the minimum energy required for a collision to be effective. Two reactions, P and Q, have activation energies of 50 kJ mol^-1 and 100 kJ mol^-1, respectively. Both reactions…
  3. Explain4 marksStandardHydrogen peroxide decomposes slowly at room temperature into water and oxygen. The reaction is catalysed by manganese(IV) oxide. Explain, in terms of activation energy and the Boltzmann distribution, how the catalyst…
  4. Explain4 marksStandardCatalysts can be classified as homogeneous or heterogeneous. Iron is used as a heterogeneous catalyst in the Haber process for the production of ammonia. Oxides of nitrogen act as homogeneous catalysts in the…
  5. Explain4 marksStandardThe reaction between nitrogen monoxide and hydrogen is thought to occur in two steps. Step 1: 2NO(g) + H2(g) → N2O(g) + H2O(g) Step 2: N2O(g) + H2(g) → N2(g) + H2O(g) The rate equation for the reaction is: rate =…
  6. Describe5 marksStandardIn the Ostwald process, ammonia is oxidised to nitrogen monoxide. The uncatalysed reaction has a very high activation energy. A platinum catalyst is used to speed up the reaction. Describe how the catalyst increases…
  7. Compare5 marksStandardCompare the modes of action of heterogeneous and homogeneous catalysts. In your answer, refer to one specific example of each type of catalyst.
  8. Explain4 marksStandardIn a catalytic converter, oxides of nitrogen such as NO are removed from exhaust gases by reaction with carbon monoxide over a platinum catalyst. Explain, in terms of adsorption, bond weakening and desorption, how the…
  9. Describe5 marksStandardA reaction is carried out at 20 °C and again at 30 °C. The rate of reaction increases when the temperature is increased. Describe, in terms of the Boltzmann distribution and of effective collisions, why this increase…
  10. Describe5 marksStandardA reaction between two gases, X2 and Y2, takes place in a sealed flask at constant temperature. The rate of the reaction increases when the total pressure in the flask is increased. With reference to collisions…
  11. Compare5 marksStandardA reaction has an activation energy of EA. The reaction is carried out at two temperatures, T1 and T2, where T2 T1. Compare the Boltzmann distributions of molecular energies at these two temperatures, and use this to…
  12. Suggest4 marksStandardIn the Haber process, N2 and H2 react to form NH3 in the presence of an iron catalyst. The catalyst is a solid, while the reactants are gases. Suggest how the iron catalyst increases the rate of this reaction.
  13. Compare5 marksStandardA student adds 50 cm³ of dilute hydrochloric acid to 50 cm³ of sodium thiosulfate solution in a conical flask and measures the time for the mixture to become cloudy. In a second experiment, the student repeats the…
  14. Suggest4 marksStandardA reaction between two gases is carried out in a closed vessel of fixed volume. The pressure inside the vessel is increased by forcing more of one of the gaseous reactants into the vessel. The temperature is kept…
  15. Suggest4 marksStandardIn a petroleum refinery, long-chain hydrocarbons are cracked into smaller, more useful molecules. The process is carried out over a solid catalyst. Suggest, in terms of activation energy and the Boltzmann distribution…
  16. Suggest4 marksStandardA student measures the rate of the reaction between two gases at several temperatures above room temperature. The rate increases as the temperature rises. Suggest two reasons why the rate of this reaction increases…
  17. Compare5 marksStandardEthene reacts with hydrogen to form ethane. The uncatalysed reaction has a high activation energy, but in the presence of a nickel catalyst the reaction proceeds rapidly at a lower temperature. Compare the catalysed…
  18. Compare5 marksStandardA reaction between two gases in a closed flask is slow at room temperature. The temperature of the flask is increased by 20 K, and the rate of reaction increases markedly. Compare the effect of this temperature…
  19. Explain4 marksStandardA student investigates the reaction between aqueous sodium thiosulfate and dilute hydrochloric acid. Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + SO2(g) + S(s) + H2O(l) The student uses a cross drawn on paper under the…
  20. Suggest4 marksStandardIn an experiment, hydrogen and iodine monochloride react in the gas phase. State two conditions that must be satisfied for a collision between a molecule of hydrogen and a molecule of iodine monochloride to result in a…
  21. Compare5 marksStandardChlorine atoms catalyse the decomposition of ozone in the stratosphere. The uncatalysed reaction has a high activation energy. With chlorine atoms present, the reaction follows a different mechanism with a lower…
  22. Explain4 marksStandardThe reaction between bromate(V) ions and bromide ions in acid solution has an activation energy of 50 kJ mol^-1. Explain, in terms of the Boltzmann distribution and the concept of activation energy, why increasing the…
  23. Explain4 marksStandardA reaction has an activation energy, EA, of 75 kJ mol⁻¹ and is carried out at 25 °C. The temperature is increased to 45 °C. Using the Boltzmann distribution, explain why the rate of the reaction increases.
  24. Explain4 marksStandardA sample of ethene, C2H4, reacts with hydrogen, H2, in a closed vessel at constant temperature. The pressure in the vessel is increased by forcing more hydrogen into the same volume. Explain, in terms of collisions…
  25. Suggest4 marksStandardA reaction between substances A and B has the overall equation: A + 2B → C + D A proposed two-step mechanism is: Step 1: A + B → X (slow) Step 2: X + B → C + D (fast) Suggest the rate equation for this reaction…
  26. Compare5 marksStandardTwo sealed flasks, A and B, of equal volume contain the same gaseous mixture of hydrogen and iodine at the same temperature. The total pressure in flask A is 100 kPa and in flask B is 200 kPa. The reaction occurs in…
  27. Explain4 marksStandardHydrogen peroxide decomposes slowly at room temperature: 2H2O2(aq) → 2H2O(l) + O2(g) When a small amount of aqueous iodide ions is added, the decomposition occurs much faster. Explain, with reference to activation…
  28. Describe7 marksChallengeNitrogen monoxide and oxygen react to form nitrogen dioxide: 2NO(g) + O2(g) → 2NO2(g) The following two-step mechanism is proposed for this reaction: Step 1: NO(g) + NO(g) ⇌ N2O2(g) (fast, equilibrium established) Step…
  29. Compare5 marksChallengeTwo gaseous decomposition reactions are studied. Reaction 1: N2O5 → N2O4 + 1/2 O2 Reaction 2: 2NO2 → 2NO + O2 For each reaction, the rate equation and a possible mechanism are given. Reaction 1: rate = k[N2O5] Step 1…
  30. Describe7 marksChallengeIn the reaction between H2(g) and I2(g), the activation energy is 171 kJ mol⁻¹. Explain what is meant by activation energy and, with reference to the Boltzmann distribution, why raising the temperature greatly…
  31. Suggest5 marksChallengeA reaction is thought to proceed by the following two-step mechanism. Step 1: NO2(g) + F2(g) → NO2F(g) + F(g) (slow) Step 2: NO2(g) + F(g) → NO2F(g) (fast) The overall reaction is 2NO2(g) + F2(g) → 2NO2F(g). Suggest…
  32. Compare6 marksChallengeEthene reacts with hydrogen to form ethane: CH2=CH2(g) + H2(g) → CH3CH3(g) . The reaction is very slow at room temperature in the absence of a catalyst. A nickel catalyst is effective for this reaction. Compare the…
  33. Suggest5 marksChallengeThe enzyme sucrase catalyses the hydrolysis of sucrose to glucose and fructose. In the absence of the enzyme the reaction is extremely slow, but in its presence the reaction proceeds rapidly at body temperature…
  34. Describe7 marksChallengeCatalysts are classified as either homogeneous or heterogeneous. With reference to a named example for each type, describe the mode of action of a heterogeneous catalyst and a homogeneous catalyst.
  35. Describe7 marksChallengeA student investigates the decomposition of hydrogen peroxide, H2O2, which slowly decomposes to water and oxygen at room temperature. Adding a small amount of solid manganese(IV) oxide, MnO2, causes rapid…
  36. Describe7 marksChallengeA gaseous reaction occurs between reactants A and B: A(g) + B(g) → products Describe, in terms of the frequency of effective collisions, how the rate of this reaction is affected by each of the following changes. (i)…
  37. Explain6 marksChallengeA student adds a small amount of a soluble transition-metal salt to an aqueous reaction mixture. The rate of reaction increases, but the temperature of the mixture does not change. Explain, in terms of the Boltzmann…
  38. Describe7 marksChallengeA catalytic converter in a car exhaust speeds up the conversion of carbon monoxide and nitrogen monoxide into carbon dioxide and nitrogen. The reaction is slow at the temperatures of the exhaust gases, but becomes fast…
  39. Describe7 marksChallengeThe activation energy, EA, for a reaction is pu50 kJ mol^-1. Describe, in terms of the Boltzmann distribution and the frequency of effective collisions, how an increase in temperature increases the rate of this…
  40. Compare6 marksChallengeA reaction has an activation energy of 80 kJ mol⁻¹. At 300 K, only a small fraction of molecules have energy greater than this value. At 350 K, the rate of the reaction is significantly faster. Compare the Boltzmann…
  41. Explain6 marksChallengeA reaction between two gases is carried out at 25 °C and again at 45 °C. The rate is faster at 45 °C. Using the Boltzmann distribution and the idea of effective collisions, explain why the rate is faster at the higher…
  42. Suggest5 marksChallengeIn a sample of nitrogen and oxygen gases at room temperature, the molecules collide with each other many millions of times per second, yet the reaction between them is extremely slow. Use the Boltzmann distribution and…
  43. Suggest5 marksChallengeThe reaction between hydrogen and iodine monochloride, H2(g) + 2ICl(g) → I2(g) + 2HCl(g) is carried out in a closed container at constant temperature. The pressure of the gas mixture is increased by reducing the volume…
  44. Compare6 marksChallengeTwo experiments are set up for the reaction between aqueous Na2S2O3 and aqueous HCl. In experiment 1, the concentration of Na2S2O3 is doubled while the volume and the concentration of HCl are kept the same. In…
  45. Explain6 marksChallengeA reaction between two gases, A(g) and B(g), takes place in a closed container at constant temperature. The concentration of A is halved while the concentration of B is kept constant. Explain, in terms of collisions…