This question is about hydrocarbons - AQA - GCSE Chemistry - Question 2 - 2016 - Paper 1
Question 2
This question is about hydrocarbons.
Most of the hydrocarbons in crude oil are alkanes.
Large alkane molecules can be cracked to produce more useful molecules.
Th... show full transcript
Worked Solution & Example Answer:This question is about hydrocarbons - AQA - GCSE Chemistry - Question 2 - 2016 - Paper 1
Step 1
Give two conditions used to crack large alkane molecules.
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Answer
High temperature (around 250-900 °C)
Presence of a catalyst (such as zeolite or silica)
Step 2
Complete the sentence.
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colourless
Step 3
Complete the displayed structure of butane.
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The structure of butane is:
H H
| |
H - C - C - H
| |
H H
Step 4
Calculate the energy released by 1.0 g of decane in kJ.
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Energy released = 24.36 kJ
Step 5
Suggest one improvement to the apparatus, or the use of the apparatus, that would make the temperature increase of the water for each fuel more accurate.
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One improvement could be to use a lid on the beaker to reduce heat loss. This would ensure that more of the heat generated by the burning fuel goes into heating the water.
Step 6
Name this black substance.
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Carbon / soot
Step 7
Suggest why it is produced.
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It is produced due to incomplete combustion of the hydrocarbons being burned.
Step 8
Give two reasons why the results in Table 1 support this conclusion.
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Hexane has the highest energy release (16.80 kJ) for 0.81 g compared to the other fuels, indicating it is more efficient.
Hexane produces the least amount of smoke, or sooty residue, indicating a cleaner combustion process.
Step 9
Describe the advantages and disadvantages of using hydrogen instead of petrol in car engines.
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Advantages:
Hydrogen combustion produces only water vapor, resulting in no air pollution or greenhouse gases.
Hydrogen can reduce dependency on non-renewable petroleum resources.
Disadvantages:
Hydrogen is a gas at room temperature, making storage and transport more challenging than liquid petrol.
The current infrastructure for hydrogen refueling is limited, making it less convenient for users.
