Syllabus Edition

First teaching 2020

Last exams 2024

|

Hydrocarbons (CIE A Level Chemistry)

Exam Questions

3 hours41 questions
11 mark

Which equation represents a valid propagation step in the free radical reaction between ethane and chlorine?

  • C2H6 + Cl rightwards arrow C2H5Cl + H

  • C2H5Cl + Cl rightwards arrow C2H4Cl + HCl

  • C2H6 + H rightwards arrow C2H5 + HCl

  • C2H5 + Cl rightwards arrow C2H5Cl

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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?

 

1

To produce alkenes.

 

2

To produce smaller molecules which are in higher demand.

 

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  +  H2rightwards arrow CH3CH2OH

What type of reaction is this?

  • Acid / Base

  • Addition

  • Hydrolysis

  • Substitution

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41 mark

Which statements about alkenes are correct?

 

1

They are less reactive than alkanes towards electrophiles.

 

2

They are used as monomers for polymerisation.

 

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 rightwards arrow 8CO + 8N2 + 8H2O

  • C8H16 + 24NO rightwards arrow 8CO2 + 12N2 + 8H2O

  • C8H18 + 17NO rightwards arrow 8CO + 8 begin mathsize 16px style 1 half end style N2 + 9H2O

  • C8H18 + 25NO rightwards arrow 8CO2 + 12 begin mathsize 16px style 1 half end style 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.

3-2-e-7

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.

 

W

‘bromine reacts with alkanes by electrophilic substitution’

 

X

‘bromine reacts with alkenes by a free-radical addition mechanism’

 

Y

‘alkenes can be oxidised by acidified manganate(VII) ions’

 

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?

3-2-cie-ial-chemistry-diagram-q4medium

  • 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.

3-2-m-6

A mixture of X and Y is reacted with HBr. 

Which three structures represent three different possible products of this reaction?

A

(CH3)2CHCBr3

(CH3)2CBrCHBr2

CH3CHBrCHBrCH3

B

(CH3)2CHCBr3

(CH3)2CBrCHBr2

CH3CBr2CHBrCH3

C

(CH3)2CBrCBr3

(CH3)2CHCBr3

CH3CBr2CHBrCH3

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?

    3-2-m-7

    • 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?

     

    1

    (CH3)2C=CH2

     

    2

    CH3CH=CHCH3

     

    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?

    3-2-m-10

    • 3-2-m-10a

    • 3-2-m-10b

    • 3-2-m-10c

    • 3-2-m-10d

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    11 mark

    Limonene is an oil formed in the peel of citrus fruits.

    3-2-cie-ial-chemistry-diagram-q1hard
    Which product is formed when an excess of bromine, Br2 (l), reacts with limonene at room temperature in the dark?

    • 3-2-h-1a

    • 3-2-h-1b

    • 3-2-h-1c

    • 3-2-h-1d

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    21 mark

    Which isomer of C6H13OH gives the greatest number of different alkenes when it is dehydrated?

    • 3-2-h-2a

    • 3-2-h-2b

    • 3-2-h-2c

    • 3-2-h-2d

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    31 mark

    Acrylic acid is produced from propene, a gaseous product of oil refineries.

    3-2-h-3Which 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?

    • 3-2-h-4a

    • 3-2-h-4b

    • 3-2-h-4c

    • 3-2-h-4d

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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?

    • 3-2-h-5a

    • 3-2-h-5b

    • 3-2-h-5c

    • 3-2-h-5d

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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.

    3-2-h-7By 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?

     

    Reagent Y

    Solution Z

    A

    B

    C

    D

    Acidified K2Cr2O7

    Concentrated H2SO4

    Concentrated H2SO4

    Ethanolic NaOH

    Dilute NaOH

    Dilute H2SO4

    Dilute NaOH

    Concentrated H2SO4

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