CO NO₂ CO₂ N₂ honeycomb coated with Pt nanoparticles exhaust in exhaust out This catalytic converter is fitted in the exhaust system of a delivery van. Fig....
Question 1 Report
This catalytic converter is fitted in the exhaust system of a delivery van. Fig. 1 shows exhaust gases passing over a honeycomb coated with platinum nanoparticles. Carbon monoxide and nitrogen oxides react on the surface to form less harmful gases. Platinum is expensive, so the engineer uses a small mass spread over a large area rather than a thick layer of platinum metal. The exhaust gases are hot when the van is moving.
(a) Name the chemical property of platinum nanoparticles that allows them to increase the rate of a reaction without being used up. [1]
(b) Use Fig. 1 to give one reason why a honeycomb shape is used. [2]
(c) What happens to the activation energy when a catalyst is used? [1]
(d) Complete the word equation for one reaction in the converter: carbon monoxide + nitrogen oxide → carbon dioxide + ________. [1]
(e) Suggest why platinum nanoparticles are more economical than a sheet of platinum with the same mass. [3]
Answer Details
- (a) Platinum nanoparticles act as a catalyst. A catalyst increases reaction rate without being used up. [1 mark]
- (b) A honeycomb has a large surface area, giving exhaust gases a large area of platinum surface to contact and react on. [2 marks]
- (c) A catalyst lowers, or reduces, the activation energy. [1 mark]
- (d) The missing product is nitrogen: carbon monoxide + nitrogen oxide → carbon dioxide + nitrogen. [1 mark]
- (e) Nanoparticles have a larger surface area to volume ratio than a sheet of the same mass. More platinum atoms or active sites are exposed to the gases, so less platinum is needed to achieve a useful reaction rate and the cost is reduced. [3 marks]
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