A town council started a low-emission zone in the town centre in January 2017. Older diesel vehicles must pay to enter the zone.
The council measures the yearly mean concentration of nitrogen dioxide and of particulates at a roadside monitor in the town centre.
The table shows the results.
| Year | Mean concentration of nitrogen dioxide (μg/m3\mu\mathrm{g/m^{3}}μg/m3) | Mean concentration of particulates (μg/m3\mu\mathrm{g/m^{3}}μg/m3) |
|---|---|---|
| 2014 | 48 | 18 |
| 2015 | 47 | 18 |
| 2016 | 46 | 17 |
| 2017 | 39 | 15 |
| 2018 | 36 | 14 |
| 2019 | 35 | 14 |
Nitrogen dioxide is one of the oxides of nitrogen.
Explain how oxides of nitrogen are made in a car engine.
Calculate the percentage decrease in the mean concentration of nitrogen dioxide from 2016 to 2019.
Use the equation: percentage decrease = (decrease in concentration ÷ concentration in 2016) × 100
Give your answer to 2 significant figures.
The council says:
"The low-emission zone has improved air quality in the town centre."
Evaluate the council's statement. Use the data in the table.
Explain why particulates in the air are a problem.
51 exam-style questions on OCR GCSE Chemistry 6.3 Interpreting and interacting with earth systems, covering 6.3.1 Formation and evolution of the atmosphere, 6.3.2 The greenhouse effect and climate change, 6.3.3 Sources and problems of atmospheric pollutants, and 6.3.4 Producing potable water. Each one has a worked solution and a mark scheme showing where the marks go.