1. 1
   A student adds a small amount of solid manganese(IV) oxide to a sample of hydrogen peroxide solution and observes that bubbles of gas are produced much faster than in a separate flask of hydrogen peroxide with nothing added. After the reaction, the manganese(IV) oxide is filtered out, dried and re-weighed.

   (a)

   A student adds a small amount of manganese(IV) oxide to hydrogen peroxide solution, and bubbles of gas are produced much faster than without it. After the reaction, the manganese(IV) oxide is filtered out and its mass is found to be unchanged. What does this show manganese(IV) oxide to be?

   [1 mark]

   • AA catalyst
   • BA reactant
   • CA product
   • DAn indicator

   (b)

   What key property of a catalyst does this experiment demonstrate?

   [1 mark]

   • AIt only works at very low temperatures
   • BIt is used up completely during the reaction
   • CIt slows down every reaction it is added to
   • DIt changes the rate of a reaction but is not used up

   (c)

   Explain why the mass of the manganese(IV) oxide is found to be unchanged after the reaction, even though it clearly increased the rate of the reaction.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An industrial chemist tests the same catalyst, previously found to speed up the decomposition of hydrogen peroxide, on a completely different industrial reaction between an organic acid and an alcohol, but finds it has no effect on the rate of this second reaction.

   (a)

   An industrial chemist finds that the catalyst used to speed up the decomposition of hydrogen peroxide does not work for a completely different reaction, the reaction between an acid and an alcohol. What does this suggest about catalysts?

   [1 mark]

   • ACatalysts are always metals
   • BAll catalysts work equally well for every reaction
   • CDifferent reactions generally need different catalysts
   • DCatalysts always slow reactions down

   (b)

   Why might a company want to use a catalyst in an industrial chemical process?

   [1 mark]

   • ATo reduce the amount of product formed
   • BTo increase the rate of the reaction and reduce costs
   • CTo increase the amount of reactant needed
   • DTo make the reaction non-reversible

   (c)

   Explain why the chemist needs to find and test a different catalyst for the reaction between the acid and the alcohol, and explain why using an effective catalyst would be beneficial to the company.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A company that manufactures a chemical product on a large scale currently runs its main reaction at a very high temperature to achieve an acceptable rate, using large amounts of energy, and is investigating whether adding a catalyst could allow lower-temperature operation while keeping the same rate of reaction.

   (a)

   Define what is meant by a catalyst, and state why catalysts are considered important in industrial chemical processes.

   [3 marks]

   (b)

   Explain how adding a suitable catalyst could allow the company to run the reaction at a lower temperature while still achieving an acceptable rate of reaction, and describe the likely benefit of this to the company.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A chemistry teacher sets an assignment asking students to research and explain the role of catalysts in both laboratory reactions and large-scale industrial manufacturing processes, using the decomposition of hydrogen peroxide and the Haber process as examples.

   (a)

   Explain fully what a catalyst is and how it increases the rate of a chemical reaction, and describe why catalysts are of great importance to the chemical industry, using a named example.

   [6 marks]

   (b)

   An energy level diagram for a reaction shows the energy of reactants, the energy of products and the activation energy of the uncatalysed pathway. Explain, with reference to such a diagram, how the presence of a catalyst changes the activation energy but not the overall energy change of the reaction, and discuss why this distinction is important when explaining how catalysts increase reaction rate.

   [6 marks]

   Total for question 4: 12 marks

End of questions