This question is about the fractions obtained from crude oil - AQA - GCSE Chemistry - Question 4 - 2022 - Paper 2
Question 4
This question is about the fractions obtained from crude oil.
Crude oil is separated into fractions by fractional distillation.
The fractions obtained from crude oi... show full transcript
Worked Solution & Example Answer:This question is about the fractions obtained from crude oil - AQA - GCSE Chemistry - Question 4 - 2022 - Paper 2
Step 1
Explain how these fractions are obtained from crude oil by fractional distillation.
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Answer
Crude oil is heated to vaporize the hydrocarbons. There is a temperature gradient in the fractional column, which means it is cooler at the top. As vapor rises, it condenses at different levels depending on boiling points. Therefore, the heavier fractions like lubricating oil condense lower down, while lighter fractions such as naphtha and petroleum gases condense at higher levels.
Step 2
Which two are useful materials produced from this feedstock?
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Answer
Detergents and solvents.
Step 3
Complete the equation for the complete combustion of C₈H₂₀.
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Answer
C₈H₂₀ + 12.5 O₂ → 8 CO₂ + 10 H₂O
Step 4
Explain why sulfur impurities are removed before petrol is burned in car engines.
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Answer
Sulfur impurities can produce sulfur dioxide when burned, which contributes to acid rain and respiratory problems, making it essential to remove them to minimize environmental and health impacts.
Step 5
Justify the student’s prediction.
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Answer
As molecular size increases, viscosity tends to increase. Therefore, heavy fuel oil, consisting of larger molecules than kerosene, is expected to be more viscous.
Step 6
Name the process which produces smaller hydrocarbon molecules from heavy fuel oil.
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Answer
Cracking.
Step 7
Give the conditions used in this process.
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High temperature (typically between 300°C and 900°C) and the presence of steam or a catalyst.
Step 8
Which pair of hydrocarbon molecules would both turn bromine water colourless?
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