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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 replenished through sustainable forestry practices.
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Burning wood is carbon-neutral, as the amount of carbon dioxide released during combustion is offset by the carbon dioxide absorbed while the trees were growing.
Step 2
Explain the process by which carbon monoxide can be produced when methane is burned.
Answer
Carbon monoxide is produced during the incomplete combustion of methane. This occurs when there is insufficient oxygen available for the combustion reaction, leading to a situation where not all the methane is converted into carbon dioxide and water. Instead, some methane is partially oxidized, resulting in the formation of carbon monoxide.
Step 3
Step 4
Calculate the volume of unreacted oxygen.
Answer
According to the stoichiometry of the burning of propane:
We start with 7.25 dm³ of oxygen. The reaction produces 3.60 dm³ of carbon dioxide.
Using the reaction equation, we know:
- The ratio of oxygen used to carbon dioxide produced is 5:3.
Calculating the amount of oxygen required for 3.60 dm³ of carbon dioxide:
ext{Oxygen needed} = 3.60 imes rac{5}{3} = 6.00 ext{ dm}^3
Thus: Unreacted oxygen = Initial oxygen - Oxygen used
Unreacted oxygen = 7.25 dm³ - 6.00 dm³ = 1.25 dm³
Finally, converting to cm³:
1.25 dm³ = 1250 cm³.
Therefore, the volume of unreacted oxygen is 1250 cm³.