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Older cars are tested each year to measure the amount of pollutants contained in exhaust fumes - AQA - GCSE Chemistry - Question 7 - 2018 - Paper 2
Question 7
Older cars are tested each year to measure the amount of pollutants contained in exhaust fumes. Table 4 shows the maximum allowed percentages of exhaust pollutants ... show full transcript
Worked Solution & Example Answer:Older cars are tested each year to measure the amount of pollutants contained in exhaust fumes - AQA - GCSE Chemistry - Question 7 - 2018 - Paper 2
Step 1
Explain how carbon monoxide is produced when petrol is burned in car engines.
Answer
Carbon monoxide is produced during the combustion of petrol when there is incomplete combustion due to an insufficient or limited oxygen supply. This typically occurs under conditions where the air-fuel mixture is rich in fuel, meaning not all the petrol can be fully oxidized to carbon dioxide.
Step 2
Suggest two reasons why the maximum allowed percentage of carbon monoxide has been decreased for newer cars.
Answer
- There is greater public concern and awareness about the harmful effects of carbon monoxide on health and the environment.
- Advances in engine technology and the introduction of catalytic converters have allowed for cleaner emissions, necessitating lower limits for pollutants such as carbon monoxide.
Step 3
Give one reason for having a maximum allowed percentage of unburned hydrocarbons in exhaust fumes.
Answer
One reason for having a maximum allowed percentage of unburned hydrocarbons is to reduce health problems, as these compounds can contribute to respiratory illnesses and environmental pollution.
Step 4
Describe how oxides of nitrogen are produced when petrol is burned in car engines.
Answer
Oxides of nitrogen are produced when nitrogen from the atmosphere reacts with oxygen at high temperatures in the engine. This can occur during combustion when the temperatures are sufficiently high, particularly in the presence of a spark from the spark plug.
Step 6
Give two effects of atmospheric pollution which are reduced by using catalytic converters.
Answer
- Reduction of acid rain through the conversion of harmful nitrogen oxides to less harmful gases.
- Improvement of air quality by decreasing levels of carbon monoxide and unburned hydrocarbons in the atmosphere.
Step 7