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This question is about combustion of fuels - AQA - GCSE Chemistry - Question 5 - 2019 - Paper 2
Question 5
This question is about combustion of fuels. Some central heating boilers use wood as a fuel. Suggest two reasons why wood is more sustainable than natural gas as a... show full transcript
Worked Solution & Example Answer:This question is about combustion of fuels - AQA - GCSE Chemistry - Question 5 - 2019 - Paper 2
Step 1
Suggest two reasons why wood is more sustainable than natural gas as a fuel for central heating boilers.
Answer
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Wood is a renewable resource, meaning it can be replanted and grown repeatedly, while natural gas is finite and will eventually run out.
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Burning wood is carbon-neutral since the carbon dioxide released during combustion was previously absorbed by the trees as they grew, thus not contributing to the overall carbon levels in the atmosphere.
Step 2
Explain the process by which carbon monoxide can be produced when methane is burned.
Answer
Carbon monoxide can be produced during the incomplete combustion of methane when there is not enough oxygen supplied for the reaction. In this scenario, instead of fully converting methane and oxygen into carbon dioxide and water, some of the carbon atoms are only partially oxidized to form carbon monoxide.
Step 3
Step 4
Calculate the volume of unreacted oxygen.
Answer
To find the volume of unreacted oxygen, we first determine the amount of oxygen needed for the complete combustion of propane. The balanced equation indicates that 5 dm³ of oxygen are needed for 1 dm³ of propane, which produces 3 dm³ of CO₂. In this case, for 3.60 dm³ of CO₂ produced, we can determine that:
- Oxygen required for combustion = 5/3 × 3.60 dm³ = 6.00 dm³
- Given oxygen = 7.25 dm³
- Unreacted oxygen = Given oxygen - Oxygen required = 7.25 dm³ - 6.00 dm³ = 1.25 dm³ = 1250 cm³.
Thus, the volume of unreacted oxygen is 1250 cm³.