Unit 1 – Alkenes
Unit 1 - Jan 2009
Q1.
In a molecule of ethene, C2H4, how many π (pi) bonds are present?
   A     One
   B     Two
   C     Three
   D     Four
(Total for question = 1 mark)

Q2.
The mechanism of the reaction represented by the equation

is an example of
   A     Free radical substitution
   B     Free radical addition
   C     Electrophilic substitution
   D     Electrophilic addition
(Total for question = 1 mark)

Q3.
What is the systematic name for the following compound?

   A     Z-4-methylhex-2-ene
   B     E-2-ethylpent-3-ene
   C     Z-4-ethylpent-2-ene
   D     E-4-methylhex-2-ene
(Total for question = 1 mark)

Q4.
Propene reacts with hydrogen chloride gas to give mainly
   A     1-chloropropane (CH3CH2CH2Cl)
   B     2-chloropropane (CH3CHClCH3)
   C     3-chloroprop-1-ene (CH2CHCH2Cl)
   D     1,2-dichloropropane (CH3CHClCH2Cl)
(Total for question = 1 mark)

Unit 1 - Jun 2009
Q5.
Which of the following alkenes exhibits E-Z isomerism?
   A     H3CCHC(CH3)2
   B     (CH3)2CCH2
   C     H2CCHCH2CH3
   D     H3CCHCHCH3
(Total for question = 1 mark)

Q6.
This question is about hydrocarbons.
(a)  Liquefied petroleum gas (LPG) is a fuel sold as an alternative to petrol.  It is a mixture of liquefied C3 and C4 alkanes.
(i)  Suggest a reason why the alkanes are liquefied.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
(ii)  There are two C4 alkanes.
       Draw skeletal formulae of each of the C4 alkanes in the spaces provided.
       Name each alkane.
(4)

(iii)  Complete the following sentence.
(1)

Compounds with the same molecular formula but different structural formula are called .........................................

(b)  Propane, C3H8, reacts with chlorine, Cl2, in a substitution reaction.

The mechanism for this reaction is described in three stages.
(i)  Give the initiation step for this reaction and state the condition necessary for this step to occur.
(2)
Initiation step

Condition
 ............................................................................................................................................. 

(ii)  Give the TWO propagation steps for this reaction.
(2)

(iii)  Give a possible termination step for this reaction.
(1)

(c)  Myrcene, C10H16, is a naturally occurring compound which is used in perfumes.

(i)  Name the functional group in myrcene.
(1)
 ............................................................................................................................................. 
(ii)  What colour change would you observe when bromine, dissolved in an organic
        solvent, is added to myrcene?
(1)
From .............................................................................. To 

(iii)  Classify the type and mechanism of the reaction that occurs when myrcene
        reacts with bromine, Br2.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(iv)  In an experiment, 1.36 g of myrcene (molar mass: 136 g mol−1) was found to react with 0.72 dm3 of hydrogen, H2, in the presence of a nickel catalyst.
        Use this information to draw the structural formula of the product of the reaction between myrcene and hydrogen.
        [Assume the molar volume of H2 under the conditions of the experiment is
        24 dm3mol−1.]
(2)
Calculation

Hence structural formula of the product

(d)  Myrcene is one of a group of compounds related to 2-methylbut-2-ene shown below.

2-methylbut-2-ene undergoes addition polymerization in a similar way to ethene.

 Draw the structural formula of the repeat unit of the polymer formed.
(2)

(Total for question = 19 marks)

Unit 1 - Jan 2010
Q7.
Chloroethane, C2H5Cl, can be made from either ethane or ethene.
(a) (i) What reagent and condition would be used to make chloroethane from ethane?
(2)
Reagent
 ............................................................................................................................................. 
Condition
 ............................................................................................................................................. 
(ii) State the type of reaction and mechanism by which this reaction occurs.
(2)
 ............................................................................................................................................. 
(b) (i) What reagent would be used to make chloroethane from ethene?
(1)
 ............................................................................................................................................. 
(ii) Show, in full, the mechanism for this reaction in which ethene is converted to chloroethane.
(3)

(c) Which method of making chloroethane has
(3)
•   a higher atom economy?
 ............................................................................................................................................. 
•   a higher percentage yield?
 ............................................................................................................................................. 
 Explain your answers.
Higher atom economy
 ............................................................................................................................................. 
 ............................................................................................................................................. 
Higher percentage yield
 ............................................................................................................................................. 
 ............................................................................................................................................. 
(d) The compound chloroethene, CH2=CHCl, forms an addition polymer.
(i) Draw a diagram, using dots or crosses, to show the arrangement of electrons in chloroethene. Only the outer shell electrons need be shown.
(2)

(ii) Chloroethene can form an addition polymer. Write the displayed formula of poly(chloroethene) showing two repeat units.
(1)

*(iii) Poly(chloroethene) is commonly known as PVC. Almost a quarter of the PVC which is manufactured is used to make water pipes, which were formerly made of metal.

                     Give TWO factors which have to be considered when deciding which material, PVC or metal, contributes to more sustainable uses of resources in the long term.
(2)
 ............................................................................................................................................. 
............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
(Total for question = 16 marks)

Q8.
This question is about hexane, C6H14, and hex-1-ene, C6H12.
(a) What test would you use to distinguish between hexane and hex-1-ene? Give the results of the test for each substance.
(2)
Test:
 ............................................................................................................................................. 
 ............................................................................................................................................. 
Result with hexane:
 ............................................................................................................................................. 
 ............................................................................................................................................. 
Result with hex-1-ene:
 ............................................................................................................................................. 
 ............................................................................................................................................. 
(b) Hex-1-ene has a number of isomers, including two stereoisomers of hex-2-ene.
(i) Complete the formula to show the structure of E-hex-2-ene.
(1)

*(ii) Explain why stereoisomerism can occur in alkenes, and why hex-2-ene has stereoisomers but hex-1-ene does not.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (c) The enthalpy change of combustion of hexane was measured using a spirit burner to heat a known mass of water in a calorimeter. The temperature rise of the water was measured. The results of the experiment are shown below.

The specific heat capacity of water is 4.18 J g−1°C−1.
(i) Calculate the energy in joules produced by burning the hexane. Use the expression
                  energy transferred = mass x specific heat capacity x temperature change.
(1)

(ii) Calculate the enthalpy change of combustion of hexane. The mass of 1 mole of hexane is 86 g.

    Give your answer to TWO significant figures. Include a sign and units in your answer.
(3)

(iii) The value for the enthalpy change of combustion in this experiment is different from the value given in data books. Suggest TWO reasons for this difference.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (iv) A student suggested that the results would be more accurate if a thermometer which read to 0.1°C was used. Explain why this would not improve the accuracy of the result. A calculation is not required.
(1)
 ............................................................................................................................................. 
(d) Hex-1-ene can be converted to hexane in the following reaction.

(i) What catalyst is used in this reaction?
(1)
 ............................................................................................................................................. 
(ii) The enthalpy change of this reaction ΔHreaction can be calculated from the following enthalpy changes of combustion.

     Complete the Hess cycle by adding labelled arrows. Use your cycle to calculate the enthalpy change ΔHreaction.
(3)

(iii) The enthalpy change for the reaction of some other alkenes with hydrogen is shown below.

     Explain why the values are so similar.
(1)
 ............................................................................................................................................. 
 (Total for question = 17 marks)

Q9.
This question is about the organic compounds with skeletal formulae as shown:

(a) Which compound is 2-methylpropane?
(1)
   A      
   B      
   C      
   D      
(b) Which compound has the molecular formula C5H12?
(1)
   A      
   B      
   C      
   D      
(c) Which compounds are isomers?
(1)
   A      compound A and compound C
   B      compound B and compound C
   C      compound B and compound D
   D      compound C and compound D
(d) Which compound reacts with acidified potassium manganate(VII) to form a diol?
(1)
   A      
   B      
   C      
   D      
(Total for question = 4 marks)
Q10.
The structural formula of 5-chloro-2,2-dimethylhexane is

(Total for question = 1 mark)
Unit 1 - Jun 2010
Q11.
Which of these statements about carbon-carbon double bonds is false?
   A     The two ends of a molecule cannot rotate relative to each other, about the axis of the double bond.
   B     They are twice as strong as a carbon-carbon single bond.
   C     They have a higher electron density than a single bond.
   D     They consist of a sigma bond and a pi bond.
(Total for question = 1 mark)

Q12.
This question is about ethene and related compounds.
(a) One way to manufacture ethene is by cracking hydrocarbon molecules such as liquid paraffin.
(i)  Name a raw material from which liquid paraffin can be obtained.
(1)
 ............................................................................................................................................. 
(ii)  Describe what is meant by cracking.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (iii)  It was proposed to set up the apparatus below on a laboratory bench, in order to
       crack paraffin.

State TWO of the risks of using the apparatus in this way and suggest how you
 would amend the set-up to minimise each risk..
(4)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
............................................................................................................................................. 
 ............................................................................................................................................. 
(b) Study the reaction scheme below and then answer the questions that follow.

(i)  Name the reagent and catalyst needed for Reaction 1.
(2)
Reagent
 ............................................................................................................................................. 
Catalyst
 ............................................................................................................................................. 
(ii)  Give the name and displayed formula of compound X.
(2)
Name
 ............................................................................................................................................. 
Displayed formula

(iii)  Describe what colour change you would see during Reaction 4 if a small amount of acidified KMnO4(aq) was shaken with ethene.
(1)
From............................................................................................to................................................................
(c)  (i)  Use displayed formulae to show the mechanism for Reaction 3.
(3)

(ii)  Explain why the alkene, propene, could form two products when it reacts with hydrogen bromide in a similar way.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (d) The formula of the alkene phenylethene, often called styrene, is shown below. It can be used to make the polymer poly(styrene).

Draw a section of the poly(styrene) polymer chain formed from two monomer units.
(2)

(e) The table below shows some data used in a life cycle analysis of polystyrene and paper drinking cups.

(i)  Some people argue that using a polystyrene cup has less environmental impact than using a paper cup.
Choose TWO pieces of data to support this argument, explaining your choices.
(2)
 ............................................................................................................................................. 
 (ii)  Suggest TWO further pieces of information, not given in the table, regarding the life cycle of the cups that would make any assessment of the environmental impact more reliable.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (Total for question = 22 marks)

Q13.
What is the correct name for the compound below?

   A     E-2,3-dibromopent-2-ene
   B     E-2,3-dibromopent-3-ene
   C     Z-2,3-dibromopent-3-ene
   D     Z-2,3-dibromopent-2-ene
(Total for question = 1 mark)

Unit 1 - Jan 2011
Q14.
Alkenes are unsaturated hydrocarbons which, because of their reactivity, are important industrial starting materials. Alkenes for industrial use are obtained by cracking alkanes.
(a) Write the equation for the cracking of decane (C10H22) to form 1 molecule of propene as the only alkene.
(1)

(b) The carbon–carbon double bond in alkenes consists of a σ and a π bond.
(i) Explain, using diagrams, the difference between the σ and the π bond in the carbon–carbon double bond of an alkene.
(4)
Diagrams

Explanation
 ............................................................................................................................................. 
 ............................................................................................................................................. 
............................................................................................................................................. 
(ii) State the type and mechanism involved in the typical reaction of alkenes.
(1)
 ............................................................................................................................................. 
*(iii) By considering the strength and structure of the π bond, explain why alkenes are more reactive than alkanes.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (c) When propene reacts with hydrogen bromide, there are two possible products.
(i) Draw a displayed formula of each of these products and label the major product.
(2)

(ii) Give the mechanism for the reaction of propene with hydrogen bromide which forms the major product.
(3)

(iii) Explain, by referring to the mechanism, why the major product is formed.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (d) The polymer poly(propene) is manufactured from propene.
(i) Write an equation for the polymerization, drawing the displayed formula of the repeat unit of poly(propene).
(3)

(ii) UV radiation causes poly(propene) to degrade. Suggest one advantage and one disadvantage of this.
(2)
Advantage
 ............................................................................................................................................. 
Disadvantage
 ............................................................................................................................................. 
 (Total for question = 20 marks)

Q15.
The correct name for the compound shown below is

   A     2-methylbut-3-ene
   B     3-methylbut-2-ene
   C     3-methylbut-3-ene
   D     2-methylbut-2-ene
(Total for question = 1 mark)

Unit 1 - Jun 2011
Q16.
This question concerns the reaction of hydrogen bromide with propene.
(a) This reaction requires
(1)
   A    normal laboratory conditions.
   B    the presence of UV light.
   C    the presence of a suitable catalyst.
   D    heating under reflux.

(b) The reaction is best described as
(1)
   A    nucleophilic substitution.
   B    electrophilic substitution.
   C    nucleophilic addition.
   D    electrophilic addition.
(c) The major product of the reaction will be
(1)
   A    1-bromopropane
   B    2-bromopropane
   C    1,2-dibromopropane
   D    2-bromopropene
(Total for Question = 3 marks)

Unit 1 - Jan 2012
Q17.
(a) The alkenes have the general formula CnH2n. However, a compound with this general formula is not necessarily an alkene. Suggest why this is so.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (b) Give the equation, using skeletal formulae, for the reaction of propene with each of the following.
     (i)   Hydrogen:
(1)

    (ii)   Hydrogen bromide to form the major product:
(2)

(c) Give the mechanism for the reaction of propene with hydrogen bromide, HBr, to form the major product.
(3)

(Total for question = 7 marks)

Q18.
Name the alkene shown below.

   A       Z-4-ethylhex-4-ene
   B       E-3-ethylhex-2-ene
   C       Z-3-ethylhex-2-ene
   D       E-3-propylpent-2-ene
(Total for question = 1 mark)

Q19.
In the reaction between ethene and bromine, the bromine molecule acts as an electrophile.

Which of the following statements is true?
   A       Ethene acts as a nucleophile because it is polar.
   B       Ethene acts as a nucleophile because it can donate a pair of electrons to bromine.
   C       Ethene is not a nucleophile in this reaction.
   D       Ethene acts as a nucleophile because it donates a single electron to bromine.
(Total for question = 1 mark)

Q20.
If propene, CH3CH==CH2, is reacted with aqueous acidified potassium manganate(VII) the organic product is
   A       CH3CH(OH)CH2OH
   B       CH3CH(OH)CH3
   C       HOCH2CH2CH2OH
   D       CH3CH2CH2OH
(Total for question = 1 mark)
Unit 1 - Jun 2012
Q21.

(a) Give the general formula for the homologous series of alkenes.
(1)
 ............................................................................................................................................. 
(b) What is meant by the term unsaturated as applied to alkenes?
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (c) (i) Name the alkene below using E-Z nomenclature.

(2)
 ............................................................................................................................................. 
     (ii) Suggest why this alkene cannot be named using the cis-trans naming system. 
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (d) Give the structural formula of the organic product of the reaction of ethene, CH2CH2, with
     (i) hydrogen.
(1)

     (ii) chlorine.
(1)

     (iii) acidified aqueous potassium manganate.(VII)
(1)

     (iv) bromine water.
(1)

(e) Draw the mechanism for the reaction of propene with hydrogen bromide to give the major product.
(4)

(f) The structure below shows two repeat units of a polymer.

     (i) Give the displayed formulae of two isomeric alkenes, either of which could have given rise to this polymer.
(2)

     (ii) State why the empirical formula of a poly(alkene) is the same as that of the monomer from which it is produced.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
     (iii) State, with a reason, the atom economy for the production of a poly(alkene) from an alkene.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (Total for question = 17 marks)

Q22.
 A compound Z contains, by mass, 26.7% carbon, 2.2% hydrogen, and 71.1% oxygen. The empirical formula of Z is
   A    CHO2
   B    C2H2O4
   C    CHO
   D    C2H2O2
(Total for question = 1 mark)

Unit 1 - Jan 2013
Q23.
Four of the reactions of propene are shown on the diagram below.

(a)  Nickel is often used as the catalyst for Reaction 1. Use your Periodic Table to select which of the following metals can be used instead of nickel to catalyse Reaction 1.
(1)
   A     Potassium
   B     Calcium
   C     Gallium
   D     Palladium
(b)  Nickel is often used as the catalyst for Reaction 1.  Use your Periodic Table to select which of the following metals can be used instead of nickel to catalyse Reaction 1.
(1)

(c)  What is formed in Reaction 3?
(1)
   A     Only 1-bromopropane
   B     Only 2-bromopropane
   C     A mixture of bromopropanes containing mainly 2-bromopropane
   D     A mixture of bromopropanes containing mainly 1-bromopropane

(d)  A mixture of dilute sulfuric acid and which of the following reagents is needed for Reaction 4?
(1)
   A     KOH
   B     KMnO4
   C     H2O2
   D     O2

(e)  The reaction of propene in Reaction 4 can be classified both as
(1)

(Total for question = 5 marks)

Unit 1 - Jun 2013
Q24.
Alkenes are unsaturated hydrocarbons. They are used in the industrial production of many organic compounds.
(a)  Add structural formulae to the flowchart below to show the organic product formed in each addition reaction of 2-methylpropene.
(4)

(b)  Suggest a mechanism for the reaction of 2-methylpropene with bromine, Br2(l). Include curly arrows.
(3)

(c)  Ethene, C2H4, was prepared from ethanol, C2H5OH, by the following reaction

C2H5OH → C2H4 + H2O

A chemist reacted 9.2 g of ethanol, C2H5OH, and obtained 4.2 g of ethene.

Calculate the percentage yield of ethene in the reaction.
(2)

(Total for Question = 9 marks)

Q25.
This question is about ethene and its reactions.
Ethene is produced in industry by cracking.
(a)  (i)  Write the equation for the cracking of dodecane, C12H26, to produce one mole of ethene as the only alkene product.
(1)

(ii)  Draw a labelled diagram of the apparatus and materials you would use to crack dodecane and collect a sample of the gaseous alkene in the laboratory.
(4)

(b)  Draw a diagram to show the regions of electron density in both parts of the double bond between the carbon atoms in ethene. Label each region with appropriate symbols.
(2)

(c)  (i)  Give the name and structural formula for the product of the reaction between ethene and bromine, Br2(l).
(2)
Name
 ............................................................................................................................................. 
Formula

(ii)  Give the mechanism for the reaction between ethene and bromine.
(3)

(d)  Give the displayed formula for the organic product of the reaction between ethene and acidified potassium manganate(VII).
(1)

(e)  (i)  Write a balanced equation for the formation of poly(ethene) from ethene, showing the structure of the polymer clearly.
(2)

(ii)  Comment on the atom economy of the reaction in (e)(i).
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
(Total for Question = 16 marks)

Q26.
An electrophile is defined as a species that
   A    is an electron pair acceptor.
   B    is an electron pair donor.
   C    has a negative charge.
   D    has a positive charge.
(Total for Question = 1 mark)

Q27.
Which of the following compounds shows geometric (E-Z or cis-trans) isomerism?
   A    but-1-ene
   B    2-methylbut-1-ene
   C    but-2-ene
   D    2-methylbut-2-ene
(Total for Question = 1 mark)
Q28.
Which of the following alkenes exhibits E/Z isomerism?
   A    But-1-ene
   B    But-2-ene
   C    2-Methylpropene
   D    Propene
(Total for Question = 1 mark)
Q29.
The repeat unit of a polymer is shown below.

The systematic name of the alkene monomer that forms this polymer is
   A    2-methyl-3-ethylpropene
   B    2-methylpent-2-ene
   C    2-methylpent-3-ene
   D    4-methylpent-2-ene
(Total for Question = 1 mark)
Unit 1 - Jun 2014
Q30.
 This question is about isomers of C4H8.
(a)  (i)  Alkenes contain a carbon-carbon double bond, which consists of a σ bond and a π bond.
Show, and clearly label, the σ and π bonds on the diagram below.
(2)

*(ii)  Explain why the σ bond is stronger than the π bond.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(b)  (i)  Draw the structural formula of E-but-2-ene.
(1)

(ii)  Explain why but-1-ene does not exhibit E-Z isomerism.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(iii)  Describe the result of the test for the presence of a CC bond in E-but-2-ene using bromine water. Give the displayed formula of the organic product.
(2)
Test result
 ............................................................................................................................................. 
 ............................................................................................................................................. 
Displayed formula of organic product:

(c)  Another test for CC bonds is the reaction with acidified potassium manganate(VII).
Describe the result of this test using but-1-ene and give the displayed formula of the organic product.
(2)
Test result
 ............................................................................................................................................. 
 ............................................................................................................................................. 

Displayed formula of organic product:

(d)  Another isomer of C4H8 has the structure shown below.

(i)  Name this isomer.
(1)
 ............................................................................................................................................. 

(ii)  This isomer forms an addition polymer. Show the structure of this polymer by drawing two repeat units.
(1)

(e)  'Polybutene' is the name used by cosmetic companies for a mixture of poly(but-1-ene) and poly(but-2-ene).
An American "eco-cosmetics" company says that though 'polybutene' is considered a safe ingredient in lip gloss, it is non-sustainable to use it.
Suggest one reason to justify this statement.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
(Total for question = 13 marks)

Q31.
Which of the following pairs are cis-trans isomers?

   A    1 and 2
   B    1 and 4
   C    2 and 3
   D    3 and 4
(Total for question = 1 mark)

Q32.
Which of the following molecules does not contain a double bond?
   A    CO2
   B    C2Cl4
   C    C3F8
   D    C2H2Cl2
(Total for question = 1 mark)

Q33.
Which of the following equations shows the first step in the mechanism for the reaction between hydrogen bromide and ethene?

(Total for question = 1 mark)

Q34.
(a)  Which of the following represents a step in the mechanism during the reaction between ethene and hydrogen bromide?
(1)
   A    C2H4 + Br+ → C2H4Br+
   B    C2H4 + HBr → C2H5+ + Br−
   C    C2H4 + HBr → C2H5• + Br•
   D    C2H4 + HBr → C2H4Br− + H+
(b)  The mechanism of the reaction between ethene and hydrogen bromide is
(1)
   A    electrophilic addition.
   B    electrophilic substitution.
   C    nucleophilic addition.
   D    nucleophilic substitution.
(Total for question = 2 marks)
Q35.
This question is about the organic compounds shown below.

(a)  The compounds which are isomers are
(1)
   A    W and X
   B    W and Y
   C    W and Z
   D    X and Z
(b)  Which compound can react with chlorine to form C6H12Cl2 as the only product?
(1)
   A    Compound W
   B    Compound X
   C    Compound Y
   D    Compound Z
(c)  Which compound is reformed in the oil industry, producing one mole of a compound with formula C6H6 and four moles of hydrogen, H2, only?
(1)
   A    Compound W
   B    Compound X
   C    Compound Y
   D    Compound Z
(Total for question = 3 marks)

Q36.

Using the data in the table below, calculate the standard enthalpy change, in kJ mol−1, for the reaction between carbon disulfide, CS2, and oxygen shown in the following equation.
CS2(g) + 3O2(g) → CO2(g) + 2SO2(g)

   A    −570
   B    −790
   C    −860
   D    −1080
(Total for question = 1 mark)