5 (c) Some fractions from crude oil contain large hydrocarbon molecules - AQA - GCSE Chemistry - Question 5 - 2015 - Paper 1
Question 5
5 (c) Some fractions from crude oil contain large hydrocarbon molecules.
5 (c) (i) Hydrocarbon molecules, such as decane, can be cracked to produce smaller, more us... show full transcript
Worked Solution & Example Answer:5 (c) Some fractions from crude oil contain large hydrocarbon molecules - AQA - GCSE Chemistry - Question 5 - 2015 - Paper 1
Step 1
Hydrocarbon molecules, such as decane, can be cracked to produce smaller, more useful molecules.
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Answer
The correct formula of the third product in the cracking of decane is C₂H₄.
Step 2
Pentene is used to produce poly(pentene).
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Answer
The equation can be completed as follows:
C₅H₁₀ → (C₃H₆)ₙ
The displayed structure of poly(pentene) shows repeating units of the form:
[
C C
/ \
H H
| |
H-C-C
| |
H H
]
where n indicates the number of repeating units.
Step 3
Suggest one property of a smart polymer that is different from that of an ordinary polymer.
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Answer
A property of a smart polymer is that it has a shape memory or can return to its original shape when conditions change.
Step 4
Describe how crude oil is separated into fractions.
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Answer
Crude oil is separated into fractions through a process called fractional distillation. The crude oil is heated in a distillation column, which allows it to evaporate. The column is hotter at the bottom and cooler at the top. Different hydrocarbons cool and condense at various heights within the column, which allows them to be collected at different points according to their boiling points.
Step 5
Suggest how the use of a suspension of limestone decreases one of the environmental impacts that the waste gases would cause.
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Answer
The use of a suspension of limestone reduces the environmental impact of sulfur dioxide, which causes acid rain. When the waste gases pass through the limestone, the calcium carbonate reacts with the sulfur dioxide, neutralizing it and preventing it from entering the atmosphere.
