Question 10
HA catalytic converter in a car exhaust changes harmful gases into less harmful gases.
One reaction in the converter is:
2CO+2NO→2CO2+N2 2\mathrm{CO} + 2\mathrm{NO} \rightarrow 2\mathrm{CO_{2}} + \mathrm{N_{2}} 2CO+2NO→2CO2+N2The converter contains a ceramic honeycomb with thousands of narrow channels. The walls of the channels are coated with a very thin layer of platinum and rhodium.
a.[2]
Identify the catalysts in the converter. Give a reason for your answer.
b.[2]
Suggest two reasons why the platinum and rhodium are used as a thin layer on a honeycomb, rather than as solid lumps of metal.
c.i.[2]
Engineers measure the percentage of carbon monoxide changed into carbon dioxide as the exhaust gases pass through the converter, at different temperatures.
The graph shows the results.
Describe the pattern in the results.
c.ii.[2]
When a car is first started, the converter is cold.
Explain why very little carbon monoxide is changed when the converter is cold. Use ideas about particles and activation energy.
c.iii.[1]
Suggest why the percentage changed increases only slightly above 300 °C.
d.[2]
Engineers suggest moving the converter closer to the engine.
Suggest how this would reduce the amount of carbon monoxide released. Use the graph.
5.2 Controlling reactions Questions
56 exam-style questions on OCR GCSE Chemistry 5.2 Controlling reactions, covering 5.2.1 Measuring and interpreting rate of reaction, 5.2.2 Factors affecting rate and collision theory, and 5.2.3 Catalysts, activation energy and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.