Fig. 1Engineblockexhaustpipecatalytic convertertail-pipeexhaustgases outCO, NO, unburnthydrocarbons inhoneycomb structurecoated with catalystCO2, N2, H2Orel...
Question 1 Report
The diagram shows a catalytic converter fitted in the exhaust pipe of a delivery van. A garage student samples the exhaust gases before and after the converter has warmed up. Carbon monoxide and nitrogen oxides are harmful gases. Carbon dioxide is also measured because it is released by the combustion reaction in the engine.
| Gas | Before converter / ppm | After converter / ppm |
|---|---|---|
| carbon monoxide, CO | 1200 | 180 |
| nitrogen monoxide, NO | 640 | 95 |
| unburnt hydrocarbons | 310 | 42 |
| carbon dioxide, CO2 | 82 000 | 84 000 |
(a) Identify the part in Fig. 1 that contains the catalyst. [1]
(b) State two harmful pollutant gases shown in Table 1. [2]
(c) Use Table 1 to work out the percentage decrease in carbon monoxide concentration. [3]
(d) Complete the balanced symbol equation for the reaction that changes carbon monoxide into carbon dioxide.
........CO + ........O2 → ........CO2 [3]
(e) Explain why carbon monoxide is dangerous when breathed in. [2]
(f) When does a catalytic converter become most effective after an engine is started? [1]
(g) Give two environmental problems caused by nitrogen oxides in air. [2]
(h) State why the higher carbon dioxide value after the converter is still an environmental concern. [1]
(i) Give two properties of a catalyst that make it useful in this apparatus. [2]
Answer Details
(a) the catalytic converter / honeycomb section in the exhaust pipe [1]
(b) any two from: carbon monoxide [1]; nitrogen monoxide / nitrogen oxides [1]; unburnt hydrocarbons [1]
(c) decrease = 1200 - 180 = 1020 ppm [1]; (1020 / 1200) x 100 [1]; = 85% [1]
(d) 2CO [1] + O2 [1] -> 2CO2 [1]
(e) carbon monoxide binds to haemoglobin in blood [1]; this reduces the amount of oxygen carried around the body [1]
(f) when it has reached a high operating temperature / warmed up [1]
(g) any two from: acid rain [1]; photochemical smog [1]; damage to plants [1]; breathing irritation [1]
(h) carbon dioxide is a greenhouse gas / contributes to global warming [1]
(i) increases the reaction rate [1]; is not used up / remains chemically unchanged [1]
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