11 mark
Which equation represents a valid propagation step in the free radical reaction between ethane and chlorine?
C2H6 + Cl•
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C2H5Cl + H•C2H5Cl + Cl•
C2H4Cl• + HClC2H6 + H•
C2H5• + HClC2H5• + Cl•
C2H5Cl
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Syllabus Edition
First teaching 2020
Last exams 2024
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Hydrocarbons (CIE AS Chemistry)
Exam Questions
3 hours41 questions
21 mark
A fraction of distilled crude oil contains molecules with between 15 and 19 carbon atoms. This fraction is cracked by strong heating.
Why is this done?
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1 |
To produce alkenes. |
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2 |
To produce smaller molecules which are in higher demand. |
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3 |
To insert oxygen atoms into the hydrocarbons. |
1, 2 and 3
1 and 2
2 and 3
1 only
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31 mark
Ethene reacts with steam in the presence of sulfuric acid.
C2H4 + H2O CH3CH2OH
What type of reaction is this?
Acid / Base
Addition
Hydrolysis
Substitution
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41 mark
Which statements about alkenes are correct?
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1 |
They are less reactive than alkanes towards electrophiles. |
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2 |
They are used as monomers for polymerisation. |
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3 |
They are formed when higher alkanes are cracked. |
1, 2 and 3
1 and 2
2 and 3
3 only
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51 mark
One of the reactions taking place in a catalytic converter in a car exhaust system is between nitrogen oxide and octane (unburned petrol). The products of this reaction are non-toxic.
Which is the correct equation for the reaction?
C8H16 + 16NO
8CO + 8N2 + 8H2OC8H16 + 24NO
8CO2 + 12N2 + 8H2OC8H18 + 17NO
8CO + 8 
N2 + 9H2OC8H18 + 25NO
8CO2 + 12 N2 + 9H2O
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61 mark
When bromine reacts with propene in an organic solvent at room temperature, what is the mechanism by which the bromine attacks the propene?
Electrophilic addition
Electrophilic substitution
Nucleophilic addition
Nucleophilic substitution
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71 mark
A molecule of a polymer contained the sequence shown.
Which monomer could produce this polymer by addition polymerisation?
CHCl=CHCl
CH2=CHCl
CH3CCl=CHCl
CH3CCl=CH2
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81 mark
Four students, W, X, Y and Z, made the following statements about alkanes and alkenes.
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W |
‘bromine reacts with alkanes by electrophilic substitution’ |
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X |
‘bromine reacts with alkenes by a free-radical addition mechanism’ |
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Y |
‘alkenes can be oxidised by acidified manganate(VII) ions’ |
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Z |
‘alkenes are formed from alkanes by cracking’ |
Which two students are correct?
W and X
W and Z
X and Y
Y and Z
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91 mark
The hydrocarbon C17H36 can be cracked.
Which compound is the least likely to be produced in this reaction?
C3H8
C4H8
C8H16
C16H34
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101 mark
In the presence of ultraviolet light, ethane and chlorine react to give a mixture of products.
Which compound could be present in the mixture of products?
CH3Cl
CH3CH2CH2Cl
CH3CH2CH2CH3
CH3CH2CH2CH2CH3
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11 mark
The cracking of a single hydrocarbon molecule, CnH2n+2, produces two hydrocarbon molecules only. Each hydrocarbon product contains the same number of carbon atoms in one molecule. Each hydrocarbon product has non-cyclic structural isomers.
What is the value of n?
9
8
6
4
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21 mark
Which reaction would not give propene?
Adding excess hot concentrated sulfuric acid to propan-1-ol.
Adding warm aqueous sodium hydroxide to 2-bromopropane.
Adding warm ethanolic sodium hydroxide to 1-bromopropane.
Passing propan-2-ol vapour over heated aluminium oxide.
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31 mark
Ethene reacts with aqueous bromine to give two products, CH2BrCH2Br and CH2BrCH2OH.
Which statement about these products is correct?
Both products are obtained in this reaction by electrophilic substitution.
Both products are obtained in this reaction by nucleophilic addition.
Both products can be hydrolysed to form the same organic compound.
Both products can form hydrogen bonds with water.
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41 mark
Which hydrocarbon would not be collected in the inverted tube by heating pentane,
CH3(CH2)3CH3, in the apparatus shown?
CH4
CH3CH3
CH3CH2CH=CH2
CH3(CH2)8CH3
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51 mark
Pent-2-ene, CH3CH2CH=CHCH3, reacts in a similar way to ethene.
Pent-2-ene is reacted with cold, dilute, acidified manganate (VII) ions.
What will be produced in the greatest amount?
CH3CH2CH(OH)CH(OH)CH3
CH3CH2COCOCH3
a mixture of CH3CH2CH(OH)CH2CH3 and CH3CH2CH2CH(OH)CH3
CH3CH2COOH and CH3COOH
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61 mark
Isomers X and Y both react with HBr.
A mixture of X and Y is reacted with HBr.
Which three structures represent three different possible products of this reaction?
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A |
(CH3)2CHCBr3 |
(CH3)2CBrCHBr2 |
CH3CHBrCHBrCH3 |
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B |
(CH3)2CHCBr3 |
(CH3)2CBrCHBr2 |
CH3CBr2CHBrCH3 |
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C |
(CH3)2CBrCBr3 |
(CH3)2CHCBr3 |
CH3CBr2CHBrCH3 |
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D |
(CH3)2CBrCHBr2 |
CHBr2CBr(CH3)CH3 |
CH3CHBrCBr2CH3 |
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71 mark
During the bromination of methane, the free radical CH3• is generated and a possible terminating step of this reaction is the formation of C2H6 by the combination of two free radicals.
What could be produced in a terminating step during the bromination of propane?
1 and 2
2 and 3
1 only
2 only
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81 mark
Which alkenes, on reaction with steam at 600 K and 6 × 106 Pa pressure in the presence of a phosphoric acid catalyst, could produce an alcohol containing a chiral carbon atom?
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1 |
(CH3)2C=CH2 |
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2 |
CH3CH=CHCH3 |
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3 |
CH3CH2CH=CH2 |
1, 2 and 3
1 and 2
2 and 3
1 only
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91 mark
0.200 mol of a hydrocarbon undergoes complete combustion to give 35.2 g of carbon dioxide and 14.4 g of water as the only products.
What is the molecular formula of the hydrocarbon?
C2H4
C2H6
C4H4
C4H8
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101 mark
What is the major product formed when compound Q is warmed with excess HBr?
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11 mark
Limonene is an oil formed in the peel of citrus fruits.
Which product is formed when an excess of bromine, Br2 (l), reacts with limonene at room temperature in the dark?
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21 mark
Which isomer of C6H13OH gives the greatest number of different alkenes when it is dehydrated?
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31 mark
Acrylic acid is produced from propene, a gaseous product of oil refineries.
Which statement about acrylic acid is not correct?
Both bond angles x and y are approximately 120°.
It decolourises aqueous bromine.
It gives an orange precipitate with 2,4-dinitrophenylhydrazine reagent.
It reacts with an alcohol to give an ester.
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41 mark
Samples of 10 cm3 of each of the first four members of the alkane series are separately mixed with 70 cm3 of oxygen. Each is then burned and the total volume, V, of residual gas measured again at room temperature and pressure.
Which graph represents the results that would be obtained?
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51 mark
Use of the Data Booklet is relevant to this question.
Which compound has an Mr of 84 and will react with HBr to give a product with an Mr of 164.9?
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61 mark
Alkane X has molecular formula C4H10.
X reacts with Cl2 (g) in the presence of sunlight to produce only two different monochloroalkanes, C4H9Cl. Both of these monochloroalkanes produce the same alkene Y, and no other organic products, when they are treated with hot ethanolic KOH.
What is produced when Y is treated with hot concentrated acidified KMnO4?
CO2 and CH3CH2CO2H
CO2 and CH3COCH3
HCO2H and CH3COCH3
CH3CO2H only
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71 mark
The following diagram represents the structure of a possible polymer.
By which method might this polymer be made?
Polymerise ethene followed by hydration.
Polymerise ethene followed by oxidation with cold acidified KMnO4.
Polymerise 1,2-dichloroethene followed by hydrolysis.
Polymerise 1,2-dichloroethene followed by oxidation with cold acidified KMnO4.
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81 mark
The petrol additive tetraethyl-lead (IV), Pb(C2H5)4, is now banned in many countries. When it is completely burned in air, lead (II) oxide, CO2 and H2O are formed.
How many moles of oxygen are required to burn one mole of Pb(C2H5)4?
9.5
11
13.5
27
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91 mark
Oxidation of an alkene Y gives a diol; further oxidation gives a diketone.
What could be Y?
CH3CH=C(CH3)2
(CH3)2CHCH=CH2
C6H5CH=CHC6H5
(C6H5)2C=CHCH3
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101 mark
In a preparation of ethene, ethanol is added a drop at a time to a heated reagent Y. To purify the ethene it is bubbled through a solution Z and then collected.
What could reagent Y and solution Z be?
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Reagent Y |
Solution Z |
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A B C D |
Acidified K2Cr2O7 Concentrated H2SO4 Concentrated H2SO4 Ethanolic NaOH |
Dilute NaOH Dilute H2SO4 Dilute NaOH Concentrated H2SO4 |
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