This question is about emissions of oxides of nitrogen from petrol and diesel engines - AQA - A-Level Chemistry - Question 1 - 2020 - Paper 3
Question 1
This question is about emissions of oxides of nitrogen from petrol and diesel engines.
1. Explain how oxides of nitrogen are formed in engines.
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Worked Solution & Example Answer:This question is about emissions of oxides of nitrogen from petrol and diesel engines - AQA - A-Level Chemistry - Question 1 - 2020 - Paper 3
Step 1
Explain how oxides of nitrogen are formed in engines.
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Answer
Oxides of nitrogen (NOx) are primarily formed through the reaction of nitrogen (N₂) and oxygen (O₂) in the air, especially at high temperatures present in combustion engines. When fuels are burned, the high temperatures promote this reaction, leading to the production of NO and NO₂.
Step 2
State why it is desirable to decrease emissions of oxides of nitrogen from vehicles.
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Decreasing emissions of oxides of nitrogen is important as these compounds contribute to the formation of acid rain and can cause respiratory problems in humans. Reducing NOx emissions thus promotes environmental health and improves air quality.
Step 3
Give the oxidation state of nitrogen in each of NO₂, NH₃ and N₂.
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Answer
Oxidation state of nitrogen in:
NO₂: +4
NH₃: -3
N₂: 0
Step 4
Complete the equation for the reaction between NO₂ and NH₃.
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Answer
The balanced equation is:
2 NO₂ + 4 NH₃ → 3 N₂ + 2 H₂O
Step 5
State the meaning of the term heterogeneous catalyst.
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A heterogeneous catalyst is a catalyst that exists in a different phase than the reactants. This typically means that the catalyst is solid, while the reactants are either gases or liquids.
Step 6
Explain why carbon particulates are formed.
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Carbon particulates are formed during incomplete combustion of fuel. When there is insufficient oxygen in the combustion process, carbon does not fully oxidize to carbon dioxide (CO₂), resulting in the formation of soot or carbon particles.
