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 o... 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. In the fractional distillation column, there is a temperature gradient, with cooler temperatures at the top. As the vapor rises, the different fractions condense at different levels due to their varying boiling points. For instance, lubricating oil condenses at higher temperatures (300-350 °C) while petroleum gases remain in gaseous form at temperatures below 25 °C.
Step 2
Which two are useful materials produced from this feedstock?
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Answer
The useful materials produced from this feedstock are Detergents and Solvents.
Step 3
Complete the equation for the complete combustion of C₈H₁₈
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Answer
The balanced equation is:
ightarrow 8 CO_2 + 9 H_2O$$
Step 4
Explain why sulfur impurities are removed before petrol is burned in car engines.
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Answer
Sulfur impurities produce sulfur dioxide when burned, which can lead to acid rain and respiratory problems. Removing these impurities reduces environmental pollution and health hazards.
Step 5
Justify the student’s prediction.
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Answer
As molecular size increases, viscosity generally increases. Heavy fuel oil contains larger hydrocarbon molecules compared to kerosene, thus making it more viscous.
Step 6
Name of process and conditions used in this process.
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Answer
Name of process: Cracking
Conditions: high temperature in the range of 300 to 900 °C, often in the presence of steam and a catalyst.
Step 7
Which pair of hydrocarbon molecules would both turn bromine water colourless?
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Answer
The pair of hydrocarbon molecules that would turn bromine water colourless is C₇H₁₄ and C₈H₁₆.
