Q1.
Crude oil is a fossil fuel.
(a) Describe how crude oil is separated into fractions.
The crude oil is heated to boil the substances. The column is hotter at the bottom
vapours condense at their boiling points or at different levels.
(4)
(b) Fuel oil is one of the fractions from crude oil.
Power stations burn fuel oil to generate electricity. The waste gases from the
combustion of fuel oil contain carbon dioxide, water vapour, sulfur dioxide and
oxides of nitrogen.
The waste gases are passed through a suspension of limestone in water. Limestone
is mainly calcium carbonate.
Suggest how the use of a suspension of limestone decreases one of the
environmental impacts that the waste gases would cause.
Acid rain is caused by sulfur dioxide and they react with by calcium carbonate. The
carbon dioxide will react or dissolve in suspension of limestone
(3)
(c) Some fractions from crude oil contain large hydrocarbon molecules.
(i) Hydrocarbon molecules, such as decane, can be cracked to produce smaller,
more useful molecules.
Write the correct formula of the third product to complete the chemical
equation.
You do not need to give the name of this product.
C10H22 C5H10 + C3H8 + C2H4
decane pentene propane
(1)
(ii) Pentene is used to produce poly(pentene).
Complete the equation and the displayed structure of poly(pentene).
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(3)
(iii) Some polymers are described as smart polymers.
Suggest one property of a smart polymer that is different to that of an ordinary
polymer.
Has a shape memory.
(1)
(Total 12 marks)
Q2.
To make a plastic, such as poly(ethene), from crude oil involves many processes.
(a) Describe how crude oil is separated into fractions.
Vaporise different condensing points.
(2)
(b) Ethene is produced by cracking the hydrocarbons in the naphtha fraction.
(i) Balance the symbol equation for this reaction.
C10H22 → C4H10 + 3C2H4
decane butane ethene
(1)
(ii) Describe how cracking is carried out.
Evaporate a catalyst
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(2)
(c) Alkanes, such as butane (C4H10), do not form polymers.
Alkenes, such as ethene (C2H4), do form polymers.
Explain these statements.
Alkenes are unsaturated. Alkanes are saturated.
(2)
(d) Ethene molecules form the polymer poly(ethene). One molecule in poly(ethene) will
contain thousands of carbon atoms. The diagram represents part of a poly(ethene)
molecule.
Propene molecules form the polymer poly(propene).
Draw a diagram to represent part of a poly(propene) molecule.
(2)
(Total 9 marks)
Q3.
Crude oil is a mixture of mostly alkanes.
(a) Crude oil is separated into useful fractions by fractional distillation.
(i) Describe and explain how the mixture of alkanes is separated by fractional
distillation.
Evaporate the crude oil and condense the hydrocarbons at different boiling points.
(3)
(ii) The table gives the name and formula for each of the first three alkanes.
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Complete the table to show the formula of butane.
Name of alkane Formula
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
(1)
(b) The structural formula of methane, CH4, is:
H
│
H C H
│
H
Draw the structural formula of propane, C3H8
H H H
│ │ │
H ─C ─ C ─ C ─ H
│ │ │
H H H
(1)
(c) The relative amounts of and the market demand for some hydrocarbons from the
fractional distillation of crude oil are shown in the graph.
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(i) Why is the market demand for the C5 – C8 fraction higher than the market
demand for the C21 – C24 fraction?
C5 to C8 fraction are fuels.
(1)
(ii) Cracking is used to break down large hydrocarbon molecules into smaller
hydrocarbon molecules.
Complete the symbol equation by writing in the formula of the other
hydrocarbon.
C20H42 C16H34 + 2 C2H4
(1)
(iii) The C5 – C8 fraction has low supply and high market demand.
Suggest three ways in which the oil industry could overcome this problem.
1. Develop biofuels.
2. Cracking.
3. Develop new techniques.
(3)
(Total 10 marks)
Page 5 of 9
Mark schemes
Q1.
(a) any four from:
• (crude oil is) heated
• to evaporate / vaporise / boil (the substances / hydrocarbons)
• the column is hotter at the bottom or is cooler at the top
• (vapours / fractions) condense
• at their boiling points or at different levels.
marks can be taken from a diagram
max 3 marks for reference to cracking
allow fractional distillation allow vapours (enter the column)
allow temperature gradient or (vapours) cool as they rise
allow description e.g. vapour turns to liquid)
allow they have different boiling points
4
(b) acid rain is caused by
allow consequences of acid rain
1
sulfur dioxide or oxides of nitrogen
second marking point is dependent on first marking point
1
they react with / are neutralised by calcium carbonate or limestone
OR
global warming is caused by
carbon dioxide
carbon dioxide will react or dissolve in suspension of limestone
allow greenhouse effect is caused by or allow consequences
of global warming
1
(c) (i) C2H4
must be formula
ignore any name
1
(ii) a single bond between carbon atoms
would score 3 marks
1
other four bonds linking hydrogen atoms and C3H7 group plus two trailing
/ connecting bonds
1
n at the bottom right hand corner of the bracket
1
(iii) has a shape memory
or
(a smart polymer) can return to original shape (when conditions change)
1
[12]
Q2.
(a) vaporise / evaporate
allow boil for vaporise
1
different condensing points / temperatures
accept condense at different levels
ignore different size molecules or different densities
mention of cracking = max 1
allow boils at different temperatures and condenses for 2
marks
if no other marks awarded allow
fractional distillation for 1 mark
1
(b) (i) 3 (C2H4)
accept +C4H8
1
(ii) (decane / naphtha / hydrocarbon) vaporise / evaporate
allow crude oil
allow boil for vaporise
1
(passed over) a catalyst / alumina / porous pot
ignore other names of catalysts
1
(c) any two from:
‘they’ must be clarified
• alkanes / butane (molecules) do not have a (carbon carbon) double
bond / are saturated / have (carbon carbon) single bonds
• alkenes / ethene (molecules) have (carbon carbon) double bonds
or
are unsaturated
• alkenes / ethene molecules are able to bond to other molecules
2
(d) single bonds between carbon atoms
–C-C–
1
the -CH3 group appears on each pair of carbons on the ‘chain’
NB any double bonds = 0 marks
1
[9]
Q3.
(a) (i) heat / evaporate the crude oil / change to gas or vapour
do not accept heat with catalyst
1
cool / condense (hydrocarbons)
allow small molecules at top and / or large molecules at
bottom
1
at different temperatures / boiling points
if the answer describes cracking ‘ no marks
1
(ii) C4H10
1
(b) H H H
│ │ │
H ─C ─ C ─ C ─ H
│ │ │
H H H
1
(c) (i) C5 to C8 fraction are fuels or easier to burn or petrol (fraction)
accept C21 to C24 fraction not useful as fuels
do not accept produce more energy
1
(ii) C2H4
do not accept C4H8
1
(iii) any three from:
• use different / lighter crude oils
• develop markets for low demand fractions
• develop new techniques / equipment to use low demand fractions
as fuels
• cracking
• convert low demand fractions to high demand fractions or bigger
molecules to smaller molecules
• develop alternative / bio fuels
do not accept price
3
[10]
