Air quality was measured at three places in a city during one day. Table 9.1 shows the concentration of three pollutant gases, measured in micrograms per cu...
Question 1 Report
Air quality was measured at three places in a city during one day. Table 9.1 shows the concentration of three pollutant gases, measured in micrograms per cubic metre.
Table 9.1
| Place | Carbon monoxide | Sulfur dioxide | Oxides of nitrogen |
|---|---|---|---|
| park | 20 | 8 | 15 |
| busy road | 140 | 26 | 110 |
| near power station | 35 | 90 | 40 |
(a) State the concentration of oxides of nitrogen measured near the power station. [1]
(b) State which place had the highest concentration of carbon monoxide. [1]
(c) Suggest the main source of the carbon monoxide at that place. [1]
(d) The power station burns coal. Suggest why the sulfur dioxide concentration is highest there. [1]
(e) Calculate the difference in carbon monoxide concentration between the busy road and the park. [2]
(f) Explain why the concentrations of carbon monoxide and oxides of nitrogen are both high at the busy road. [2]
(g) Suggest one measure that could reduce these pollutants at the busy road. [1]
Answer Details
This question tests reading a data table of air pollutant concentrations and explaining the pattern.
(a) The concentration of oxides of nitrogen near the power station read straight from the table is 40 micrograms per cubic metre [1].
(b) The highest carbon monoxide concentration (140) is at the busy road [1].
(c) The main source there is exhaust gases from cars and vehicles, produced by incomplete combustion of fuel [1].
(d) The sulfur dioxide is highest near the power station because the coal it burns contains sulfur, which forms sulfur dioxide when burned [1].
(e) Difference in carbon monoxide between the busy road and the park [2]:
\(140 - 20 = 120\) micrograms per cubic metre. Award [1] for the correct subtraction and [1] for the answer 120 micrograms per cubic metre.
(f) Both gases are high at the busy road because [2]: many cars and vehicles pass along it [1]; the incomplete combustion of the fuel produces carbon monoxide, while the hot engines make oxides of nitrogen from the nitrogen and oxygen in the air [1].
(g) One measure to reduce these pollutants [1]: fit catalytic converters / reduce traffic / use electric vehicles / use public transport.
Exam tip: for a "state the concentration" mark, always quote the value with its unit exactly as given in the table.
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