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This question is about combustion of fuels - AQA - GCSE Chemistry - Question 5 - 2019 - Paper 2

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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.

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Answer

  1. Wood is a renewable resource, meaning it can be replenished over time through sustainable forestry practices.

  2. Burning wood does not increase the amount of carbon dioxide in the atmosphere, as the carbon dioxide released during combustion is offset by the carbon dioxide absorbed by the trees during their growth.

Step 2

Explain the process by which carbon monoxide can be produced when methane is burned.

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Answer

Carbon monoxide is produced during the incomplete combustion of methane, which occurs when there is insufficient oxygen available in the combustion process. Incomplete combustion leads to the formation of carbon monoxide instead of the complete combustion product, carbon dioxide.

Step 3

Balance the equation for the combustion of methane to produce carbon monoxide.

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Answer

To balance the equation for methane combusting to produce carbon monoxide, we have:

2CH4(g)+3O2(g)2CO(g)+4H2O(l)2CH_4(g) + 3O_2(g) → 2CO(g) + 4H_2O(l)

Step 4

Calculate the volume of unreacted oxygen.

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Answer

The reaction shows that 5 dm³ of oxygen is needed for every 3 dm³ of carbon dioxide produced. Given that 3.60 dm³ of carbon dioxide is produced:

ext{Oxygen needed} = rac{5 ext{ dm}^3}{3 ext{ dm}^3} imes 3.60 ext{ dm}^3 = 6.0 ext{ dm}^3

Since 7.25 dm³ of oxygen was supplied, the unreacted oxygen is:

extUnreactedoxygen=7.25extdm36.0extdm3=1.25extdm3 ext{Unreacted oxygen} = 7.25 ext{ dm}^3 - 6.0 ext{ dm}^3 = 1.25 ext{ dm}^3

Converting to cm³: 1.25extdm3=1250extcm31.25 ext{ dm}^3 = 1250 ext{ cm}^3

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