2017 · Q107
Which one of the following statements about air pollution caused by diesel engines is correct?
general-sciencebiotech-environment-science
- AIt produces large quantity of carbon monoxide at lower and high temperatures
- BIt produces large quantity of nitrogen oxides at lower and high temperatures
- CIt produces large quantity of carbon monoxide at lower temperature and nitrogen oxides at high temperature
- DIt produces large quantity of nitrogen oxides at lower temperature and carbon monoxide at high temperature
Explanation
Diesel engines run lean, so carbon monoxide – a product of incomplete combustion – forms mainly at lower temperatures, while nitrogen oxides form at high temperatures when atmospheric nitrogen oxidises (thermal NOx). This is why diesel vehicles are associated with NOx pollution while rich-running petrol engines emit more CO. Hence CO is formed at low temperature and NOx at high temperature, giving (C).