1. 1
   A technician adds a small amount of manganese(IV) oxide powder to a solution of hydrogen peroxide, which then decomposes rapidly into water and oxygen gas. When the reaction is complete, the technician finds that the mass of manganese(IV) oxide is exactly the same as before the reaction began.

   (a)

   A factory adds manganese(IV) oxide to a solution of hydrogen peroxide, which then decomposes into water and oxygen much faster than without the manganese(IV) oxide. After the reaction, the mass of manganese(IV) oxide is unchanged. What is manganese(IV) oxide acting as in this reaction?

   [1 mark]

   • AA reactant, since it takes part in the reaction
   • BA catalyst, since it speeds up the reaction without being used up
   • CA product, since it is formed during the decomposition
   • DAn inhibitor, since it slows down the reaction

   (b)

   Why does the manganese(IV) oxide increase the rate of the decomposition reaction?

   [1 mark]

   • AIt provides an alternative reaction pathway with a lower activation energy
   • BIt increases the concentration of hydrogen peroxide
   • CIt increases the temperature of the solution significantly
   • DIt reacts with the oxygen produced, removing it from the mixture

   (c)

   Explain why the mass of manganese(IV) oxide is unchanged after the reaction, and describe how this evidence supports the classification of manganese(IV) oxide as a catalyst.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A chemical engineer notes that an ammonia manufacturing plant uses an iron catalyst, while a nearby sulfuric acid plant uses a vanadium(V) oxide catalyst for its key reversible reaction, and is explaining to a trainee why different catalysts are chosen for different industrial processes.

   (a)

   A different industrial process uses a vanadium(V) oxide catalyst for one reaction and an iron catalyst for a different reaction. What does this suggest about catalysts in general?

   [1 mark]

   • AAny catalyst works equally well for every reaction
   • BCatalysts are only needed for reactions involving metals
   • CDifferent reactions need different, specific catalysts
   • DCatalysts change the products formed in a reaction

   (b)

   Why is it important for industries to use catalysts in these processes?

   [1 mark]

   • ACatalysts prevent reactions from being reversible
   • BCatalysts increase the total amount of product that can ever be made from a fixed amount of reactant
   • CCatalysts are required by law for all industrial reactions
   • DCatalysts increase the rate of reaction, reducing the time and energy needed, which reduces costs

   (c)

   Explain why using a catalyst allows an industrial plant to use a lower operating temperature than would otherwise be needed, and describe how this benefits the company financially.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates whether copper(II) oxide powder acts as a catalyst for the decomposition of hydrogen peroxide solution, by timing how long it takes to collect a fixed volume of oxygen gas, once with copper(II) oxide added and once without any copper(II) oxide present, keeping the volume and concentration of hydrogen peroxide the same in both trials.

   (a)

   A student investigates the effect of adding copper(II) oxide powder to hydrogen peroxide solution, timing how long it takes for a fixed volume of oxygen gas to be collected, with and without the catalyst present. Describe what result the student would expect if copper(II) oxide is acting as a catalyst.

   [3 marks]

   (b)

   Describe how the student could confirm, using mass measurements, that the copper(II) oxide is acting as a catalyst rather than being used up as a reactant, and explain why keeping the volume and concentration of hydrogen peroxide the same in both trials is important.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A revision class is reviewing how catalysts work at a particle level, focusing on activation energy and reaction pathways, and how this relates to the energy level diagrams they have previously studied.

   (a)

   Explain fully, using ideas about activation energy and reaction pathways, how a catalyst increases the rate of a chemical reaction without being used up itself, and describe how this effect can be represented on an energy level diagram.

   [6 marks]

   (b)

   Discuss why catalysts are considered economically and environmentally important in industrial chemistry, giving specific examples of industrial processes that rely on catalysts, and explaining the benefits catalysts provide in each case.

   [6 marks]

   Total for question 4: 12 marks

End of questions