1. 1
   A car manufacturer fits a catalytic converter containing platinum and palladium to reduce harmful exhaust gases. The platinum and palladium speed up the conversion of carbon monoxide and nitrogen oxides into less harmful gases but are not written into the balanced chemical equation for the reaction, and the same amount of platinum and palladium remains in the converter after many years of use.

   (a)

   What term describes a substance with these properties?

   [1 mark]

   • AA catalyst
   • BA reactant
   • CA product
   • DA solvent

   (b)

   An engineer is asked how she knows that the platinum and palladium in the converter are catalysts rather than reactants in the exhaust reactions. Which observation best supports this conclusion?

   [1 mark]

   • AThe converter is positioned underneath the car
   • BThe platinum and palladium are shiny metals
   • CThe exhaust gases are hot when they leave the engine
   • DThe platinum and palladium do not appear in the balanced equation and their mass does not decrease over time

   (c)

   Explain why the platinum and palladium are not included as reactants or products in the balanced chemical equation for the exhaust reactions.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In the human digestive system, the enzyme amylase breaks down starch into sugars at body temperature (around 37 degrees Celsius). A patient with a high fever has a body temperature of 40 degrees Celsius, which is above the optimum temperature at which amylase works best.

   (a)

   Amylase speeds up this reaction without being used up itself. What type of catalyst is amylase?

   [1 mark]

   • AA metal catalyst
   • BA biological catalyst (enzyme)
   • CA solvent
   • DAn indicator

   (b)

   A patient with a high fever has a body temperature of 40 degrees Celsius, above the optimum temperature at which amylase works best. What is the most likely effect of this higher temperature on the rate at which amylase breaks down starch?

   [1 mark]

   • AThe rate is unaffected by any change in temperature
   • BThe rate keeps increasing indefinitely with no limit
   • CThe rate decreases because the enzyme begins to denature
   • DThe enzyme starts to act as a reactant instead of a catalyst

   (c)

   Explain, in terms of activation energy, how a catalyst such as amylase increases the rate of a reaction.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An industrial chemist tests manganese dioxide as a possible catalyst for the decomposition of hydrogen peroxide into water and oxygen, comparing the rate of decomposition with and without the manganese dioxide present.

   (a)

   Describe an experiment the chemist could carry out to show that the manganese dioxide is acting as a catalyst and is not being chemically used up by the reaction.

   [3 marks]

   (b)

   Explain, using the ideas of activation energy and reaction pathway, why adding manganese dioxide increases the rate of decomposition of hydrogen peroxide.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A chemical engineer proposes introducing a solid catalyst into an industrial process that currently runs at a very high temperature, in order to reduce energy costs and reduce the plant's environmental impact.

   (a)

   Explain, with reference to activation energy and reaction profiles, how introducing a catalyst would allow the process to run at a lower temperature while still achieving an acceptable rate of reaction.

   [6 marks]

   (b)

   Evaluate the economic and environmental advantages and disadvantages of using catalysts in industrial chemical processes.

   [6 marks]

   Total for question 4: 12 marks

End of questions