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Isomerism

The document contains a series of chemistry questions focused on isomerism, hydrocarbon reactions, and molecular structures. It includes calculations, explanations of reactions, and mechanisms related to various organic compounds. The questions assess understanding of empirical and molecular formulas, structural isomers, and stereoisomerism among other topics.

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Abayomi Samuel Lanre

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0% found this document useful (0 votes)

31 views87 pages

Isomerism

Uploaded by

Abayomi Samuel Lanre

We take content rights seriously. If you suspect this is your content, claim it here.

Available Formats

Download as DOCX, PDF, TXT or read online on Scribd

You are on page 1/ 87

Name: ________________________

Isomerism
Class: ________________________

Date: ________________________

Time: 297 minutes

Marks: 281 marks

Comments:

Page 1 of 87
Q1.
A hydrocarbon contains 87.8% by mass of carbon and has a relative molecular mass (Mr)
of 82.0
The hydrocarbon decolourises bromine water.

Determine the empirical and molecular formulae of the hydrocarbon.

Suggest two possible structures for the hydrocarbon.
Name the type of reaction taking place when bromine water reacts with the hydrocarbon.

_______________________________________________________________________

_______________________________________________________________________
(Total 6 marks)

Q2.
How many structural isomers with an unbranched carbon chain have the molecular
formula C4H8Br2?

A 4

B 5

C 6

D 7

(Total 1 mark)

Q3.
The oxidation of propan-1-ol can form propanal and propanoic acid.
The boiling points of these compounds are shown in the table.

Compound Boiling point / °C

Page 2 of 87
propan-1-ol 97

propanal 49

propanoic acid 141

In a preparation of propanal, propan-1-ol is added dropwise to the oxidising agent and the
aldehyde is separated from the reaction mixture by distillation.

(a) Explain, with reference to intermolecular forces, why distillation allows propanal to
be separated from the other organic compounds in this reaction mixture.

___________________________________________________________________

___________________________________________________________________
(3)

(b) Give two ways of maximising the yield of propanal obtained by distillation of the
reaction mixture.

1. _________________________________________________________________

___________________________________________________________________

Page 3 of 87
2. _________________________________________________________________

___________________________________________________________________

___________________________________________________________________
(2)

(c) Describe how you would carry out a simple test-tube reaction to confirm that the
sample of propanal obtained by distillation does not contain any propanoic acid.

___________________________________________________________________

___________________________________________________________________
(2)

(d) A student carried out an experiment to determine the enthalpy of combustion of

ethanol.
Combustion of 457 mg of ethanol increased the temperature of 150 g of water from
25.1 °C to 40.2 °C

Calculate a value, in kJ mol–1, for the enthalpy of combustion of ethanol in this

experiment.
Give your answer to the appropriate number of significant figures.

(The specific heat capacity of water is 4.18 J K–1 g–1)

Enthalpy of combustion ____________________ kJ mol–1

(3)

(e) A mixture of isomeric alkenes is produced when pentan-2-ol is dehydrated in the

presence of hot concentrated sulfuric acid. Pent-1-ene is one of the isomers
produced.

Page 4 of 87
Name and outline a mechanism for the reaction producing pent-1-ene.

Name of mechanism _________________________________________________

Mechanism

(4)

(f) A pair of stereoisomers is also formed in the reaction in part (e).

Name the less polar stereoisomer formed.

Explain how this type of stereoisomerism arises.

Name _____________________________________________________________

Explanation _________________________________________________________

___________________________________________________________________

___________________________________________________________________
(2)
(Total 16 marks)

Q4.
How many structural isomers with the molecular formula C5H10O react with Tollens’
reagent?

A 3

B 4

C 5

D 6

(Total 1 mark)

Q5.
This question is about the structures of some organic molecules.

(a) Draw the skeletal formula of 3-methylbutanal.

Page 5 of 87
(1)

(b) Draw the displayed formula of C5H11Br that is the major product of the reaction of 2-
methylbut-2-ene with hydrogen bromide.

(1)

(c) Thermal cracking of hydrocarbons produces molecules that are attacked by

electrophiles because they have a region of high electron density.

Draw the structure of one of these molecules that contains four carbon atoms.

(1)
(Total 3 marks)

Q6.
How many structural isomers are there with the molecular formula C3H6BrCl?

A 4

B 5

C 6

D 7
(Total 1 mark)

Q7.
Which compound does not show stereoisomerism?

A 1,2-dichloropropene

B 1,2-dichloropropane

Page 6 of 87
C 1,3-dichloropropene

D 1,3-dichloropropane
(Total 1 mark)

Q8.
Avgas is an aviation fuel used in the internal combustion engines of helicopters.
It consists of a large number of hydrocarbons, including a high proportion of hexane,
which can exist as several isomers.

(a) Draw the skeletal formulae of two branched isomers of hexane.

(1)

(b) State the type of isomerism shown by these branched isomers.

___________________________________________________________________
(1)

(c) Safety signs on the fuselage of the helicopter state that the air inlets to the engine
need to be cleaned out regularly.

Write an equation for the combustion of hexane that would happen in the helicopter
engine if the air inlets were partially blocked with debris.

___________________________________________________________________
(2)

(d) Suggest how this partial blockage might affect the performance of the helicopter
engine.

___________________________________________________________________

___________________________________________________________________
(1)
(Total 5 marks)

Q9.
What is the total number of structural isomers with the molecular formula C2HBrClF3?

A 2

Page 7 of 87
B 3

C 4

D 5
(Total 1 mark)

Q10.
Which is a pair of functional group isomers?

(Total 1 mark)

Q11.
Z-Retinal, shown in the diagram, is a component in vitamin A.

Which of the double bonds, labelled A, B, C or D, is responsible for the letter Z in the
name?

Page 8 of 87
A

D
(Total 1 mark)

Q12.
This question is about isomerism.

(a) How many isomers are represented by the formula C5H12?

Tick (✔) one box.

(b) Name the type of structural isomerism shown by the isomers of C5H12

___________________________________________________________________
(1)

(c) 2-Hydroxypropanenitrile displays optical isomerism.

Draw three-dimensional representations of the two enantiomers of 2-

hydroxypropanenitrile, showing how the two structures are related to each other.

(2)

(d) Describe how separate samples of each of these enantiomers could be

distinguished.

___________________________________________________________________

___________________________________________________________________
(2)

(e) Butan-2-ol reacts with concentrated sulfuric acid to produce three isomeric alkenes.

Page 9 of 87
Name and outline a mechanism to show how any one of the alkenes is formed.

Explain how this reaction can lead to the formation of each of these three alkenes.

Name of mechanism __________________________________________________

Mechanism

Explanation ________________________________________________________

___________________________________________________________________

___________________________________________________________________
(8)
(Total 13 marks)

Q13.
When methylbenzene reacts with ethanoyl chloride in the presence of aluminium chloride,
the product, H, is formed.

Page 10 of 87
(a) Deduce the molecular formula of H.

___________________________________________________________________
(1)

(b) Two other isomers are also produced in the reaction.

Draw the structure of one of the other isomers.

Name the type of structural isomerism shown by these three products.

Structure

Type of isomerism __________________________________________________

(2)

Include an equation for the formation of the reactive intermediate that is involved in
the reaction.

Name _____________________________________________________________

Equation ___________________________________________________________

Mechanism

Page 11 of 87
(5)
(Total 8 marks)

Q14.
Compound J, known as leaf alcohol, has the structural formula
CH3CH2CH=CHCH2CH2OH and is produced in small quantities by many green plants.
The E isomer of J is responsible for the smell of freshly cut grass.

(a) Give the structure of the E isomer of J.

(1)

(b) Give the skeletal formula of the organic product formed when J is dehydrated
using concentrated sulfuric acid.

(1)

(c) Another structural isomer of J is shown below.

Explain how the Cahn-Ingold-Prelog (CIP) priority rules can be used to deduce the
full IUPAC name of this compound.

___________________________________________________________________

Page 12 of 87
___________________________________________________________________

___________________________________________________________________
(6)

(d) The effect of gentle heat on maleic acid is shown below.

A student predicted that the yield of this reaction would be greater than 80%.

In an experiment,10.0 g of maleic acid were heated and 6.53 g of organic product

were obtained.

Is the student correct? Justify your answer with a calculation using these data.

___________________________________________________________________

___________________________________________________________________
(2)
(Total 10 marks)

Q15.
2-bromo-2-methylpentane is heated with potassium hydroxide dissolved in ethanol. Two
structural isomers are formed.

(a) State the meaning of the term structural isomers.

___________________________________________________________________

___________________________________________________________________
(1)

(b) Name and draw the mechanism for the formation of one of the isomers.

Name of mechanism __________________________________________________

Mechanism

Page 13 of 87
(5)
(Total 6 marks)

Q16.
Dodecane (C12H26) is a hydrocarbon found in the naphtha fraction of crude oil. Dodecane
can be used as a starting material to produce a wide variety of useful products. The
scheme below shows how one such product, polymer Y, can be produced from dodecane.

(a) Name the homologous series that both C2H4 and C4H8 belong to.
Draw a functional group isomer of C4H8 that does not belong to this homologous
series.

Name _____________________________________________________________

Functional group isomer

(2)

(b) Identify compound X.

___________________________________________________________________
(1)

(c) Name polymer Y.

Page 14 of 87
___________________________________________________________________
(1)

(d) Reaction 1 is an example of thermal cracking and is carried out at a temperature of

750 °C.

State one other reaction condition needed.

___________________________________________________________________
(1)

(e) Reaction 2 is exothermic. A typical compromise temperature of 200 °C is used

industrially for this reaction.

Explain the effect of a change of temperature on both the position of equilibrium and
the rate of reaction, and justify why a compromise temperature is used industrially.

___________________________________________________________________

___________________________________________________________________
(6)
(Total 11 marks)

Q17.
Isooctane (C8H18) is the common name for the branched-chain hydrocarbon that burns
smoothly in car engines. The skeletal formula of isooctane is shown below.

(a) Give the IUPAC name for isooctane.

___________________________________________________________________
(1)

(b) Deduce the number of peaks in the 13C NMR spectrum of isooctane.

Page 15 of 87
6

8
(1)

(c) Isooctane can be formed, together with propene and ethene, in a reaction in which
one molecule of an alkane that contains 20 carbon atoms is cracked.

Using molecular formulas, write an equation for this reaction.

___________________________________________________________________
(1)

(d) How do the products of the reaction in part (c) show that the reaction is an example
of thermal cracking?

___________________________________________________________________
(1)

(e) Deduce the number of monochloro isomers formed by isooctane.

Draw the structure of the monochloro isomer that exists as a pair of optical isomers.

Number of monochloro isomers

___________________________________________________________________

Structure

(2)

(f) An isomer of isooctane reacts with chlorine to form only one monochloro compound.

Draw the skeletal formula of this monochloro compound.

(1)

(g) A sample of a monochlorooctane is obtained from a comet. The chlorine in the

monochlorooctane contains the isotopes 35Cl and 37Cl in the ratio 1.5 : 1.0

Page 16 of 87
Calculate the Mr of this monochlorooctane.

Mr = _______________
(2)

(h) Isooctane reacts with an excess of chlorine to form a mixture of chlorinated

compounds.
One of these compounds contains 24.6% carbon and 2.56% hydrogen by mass.
Calculate the molecular formula of this compound.

Molecular formula = _______________

(3)
(Total 12 marks)

Q18.
How many isomers have the molecular formula C5H12?

A 2

B 3

C 4

D 5
(Total 1 mark)

Q19.
How many structural isomers have the molecular formula C4H9Br?

A 2

B 3

Page 17 of 87
C 4

D 5
(Total 1 mark)

Q20.
How many secondary amines have the molecular formula C4H11N?

A 2

B 3

C 4

D 5
(Total 1 mark)

Q21.
The alkene 3-methylpent-2-ene (CH3CH=C(CH3)CH2CH3) reacts with hydrogen bromide to
form a mixture of 3-bromo-3-methylpentane and 2-bromo-3-methylpentane.

(a) The alkene 3-methylpent-2-ene (CH3CH=C(CH3)CH2CH3) exists as E and Z

stereoisomers.

Draw the structure of Z-3-methylpent-2-ene.

(1)

(b) Name and outline the mechanism for the formation of 3-bromo-3-methylpentane
from this reaction of 3-methylpent-2-ene with hydrogen bromide.

Explain why more 3-bromo-3-methylpentane is formed in this reaction than 2-bromo-

3-methylpentane.

___________________________________________________________________

Page 18 of 87
___________________________________________________________________

___________________________________________________________________

___________________________________________________________________
(7)
(Total 8 marks)

Q22.
The structure of cyclohexene is shown.

Which of the following is the general formula of cyclic alkenes such as cyclohexene?

A CnH2n–4

B CnH2n–2

C CnH2n

D CnH2n+2
(Total 1 mark)

Q23.
(a) Octane (C8H18) is an important compound in petrol.

(i) Identify the homologous series to which octane belongs.

______________________________________________________________
(1)

(ii) Write an equation to show the complete combustion of C8H18

______________________________________________________________
(1)

(iii) An isomer of octane used to improve the performance of car engines is

shown.

Page 19 of 87
Give the IUPAC name of this isomer.

______________________________________________________________
(1)

(b) Compound X is produced when an alkane is cracked.

(i) Give the IUPAC name for compound X.

______________________________________________________________
(1)

(ii) One molecule of an alkane is cracked to produce one molecule of compound

X, one molecule of octane and one molecule of ethene.

Deduce the molecular formula of this alkane.

______________________________________________________________
(1)

(iii) Name the type of cracking that produces a high yield of compound X.
Give two conditions required for this process.

Type of cracking ________________________________________________

Conditions _____________________________________________________

______________________________________________________________
(2)

(iv) Compound X has several isomers. The structure of X is repeated here.

Draw the displayed formula of a chain isomer, a position isomer and a

functional group isomer of compound X.

Displayed formula of isomer of

Type of isomer
compound X

Page 20 of 87
Chain

Position

Functional group

(3)
(Total 10 marks)

Q24.
Two reactions of 2-bromopentane, (CH3CH2CH2CHBrCH3) are shown.

The C5H10 formed in reaction 1 exists as a mixture of three isomers, one of which is pent-
1-ene. Two of the isomers are a pair of stereoisomers. All three isomers decolourise
bromine.

(a) The same reagent is used in both reactions. The product is determined by the
choice of conditions.

State the reagent and the conditions for each of reaction 1 and reaction 2.

State the role of the reagent in each reaction.

Name and outline the mechanism of reaction 1 for the formation of pent-1-ene.

___________________________________________________________________

Page 21 of 87
___________________________________________________________________
(8)

(b) All three isomers of C5H10 contain the same functional group.

Draw the displayed formula of pent-1-ene.

Draw the structures of the pair of stereoisomers and give their full IUPAC names.

Explain the origin of the stereoisomerism shown.

___________________________________________________________________

___________________________________________________________________
(5)

(c) The rates of hydrolysis of two chloroalkanes can be investigated by adding aqueous
silver nitrate to the chloroalkanes. During the hydrolysis reactions, chloride ions are
liberated slowly. Precipitates of silver chloride are formed.

Outline a method to compare the rate of hydrolysis of 1-chlorobutane with that of 2-

chlorobutane. State how the method would ensure a fair test.

___________________________________________________________________

Page 22 of 87
___________________________________________________________________

___________________________________________________________________

___________________________________________________________________
(4)
(Total 17 marks)

Q25.
Central heating fuel, obtained by the fractional distillation of crude oil, contains saturated
hydrocarbons with the molecular formula C16H34

(a) Give the meaning of the terms saturated and hydrocarbon as applied to saturated
hydrocarbons.

Saturated __________________________________________________________

___________________________________________________________________

Hydrocarbon ________________________________________________________

___________________________________________________________________
(2)

(b) If the boiler for a central heating system is faulty, a poisonous gas may be produced
during the combustion of C16H34

Write an equation for the reaction that forms this poisonous gas and one other
product only.

___________________________________________________________________
(1)

(c) Explain why the sulfur compounds found in crude oil should be removed from the
fractions before they are used for central heating fuel.

___________________________________________________________________

___________________________________________________________________
(2)

(d) A hydrocarbon C16H34 can be cracked to form C8H18, ethene and propene.

(i) Write an equation to show this cracking reaction.

Page 23 of 87
______________________________________________________________
(1)

(ii) Suggest one important substance manufactured on a large scale from

propene.

______________________________________________________________
(1)

(iii) Draw the displayed formula of the functional group isomer of propene.

(1)

(e) There are many structural isomers with the molecular formula C8H18

Draw the structure of 2,3,3-trimethylpentane.

(1)

(f) A compound C8H18 reacts with chlorine to give several haloalkanes.

Give the IUPAC name of the following haloalkane.

___________________________________________________________________
(1)

Page 24 of 87
(Total 10 marks)

Q26.
Some oil-fired heaters use paraffin as a fuel.
One of the compounds in paraffin is the straight-chain alkane, dodecane (C12H26).

(a) Give the name of the substance from which paraffin is obtained.
State the name of the process used to obtain paraffin from this substance.

Substance __________________________________________________________

Process ____________________________________________________________
(2)

(b) The combustion of dodecane produces several products.

Write an equation for the incomplete combustion of dodecane to produce gaseous

products only.

___________________________________________________________________
(1)

(i) Explain how these oxides of nitrogen are formed.

______________________________________________________________

______________________________________________________________
(2)

(ii) Write an equation to show how nitrogen monoxide in the air is converted into
nitrogen dioxide.

______________________________________________________________
(1)

(iii) Nitric acid (HNO3) contributes to acidity in rainwater.

Deduce an equation to show how nitrogen dioxide reacts with oxygen and
water to form nitric acid.

______________________________________________________________
(1)

(d) Dodecane (C12H26) can be cracked to form other compounds.

(i) Give the general formula for the homologous series that contains dodecane.

______________________________________________________________
(1)

Page 25 of 87
(ii) Write an equation for the cracking of one molecule of dodecane into equal
amounts of two different molecules each containing the same number of
carbon atoms.
State the empirical formula of the straight-chain alkane that is formed.
Name the catalyst used in this reaction.

Equation ______________________________________________________

Empirical formula of alkane ________________________________________

Catalyst _______________________________________________________

______________________________________________________________
(3)

(iii) Explain why the melting point of dodecane is higher than the melting point of
the straight-chain alkane produced by cracking dodecane.

______________________________________________________________

______________________________________________________________
(2)

(e) Give the IUPAC name for the following compound and state the type of structural
isomerism shown by this compound and dodecane.

IUPAC name ________________________________________________________

Type of structural isomerism ____________________________________________

(2)

(f) Dodecane can be converted into halododecanes.

Deduce the formula of a substance that could be reacted with dodecane to produce
1-chlorododecane and hydrogen chloride only.

___________________________________________________________________
(1)
(Total 16 marks)

Q27.
The following table gives the names and structures of some structural isomers with the
molecular formula C5H10.

Page 26 of 87
Name of isomer Structure

Isomer 1 pent-2-ene CH3CH = CHCH2CH3

Isomer 2 cyclopentane

Isomer 3 3-methylbut-1-ene (CH3)2CHCH = CH2

Isomer 4 2-methylbut-2-ene (CH3)2C = CHCH3

Isomer 5 2-methylbut-1-ene H2C = C(CH3)CH2CH3

(a) Isomer 1 exists as E and Z stereoisomers.

(i) State the meaning of the term stereoisomers.

______________________________________________________________

______________________________________________________________
(2)

(ii) Draw the structure of the E stereoisomer of Isomer 1.

(1)

(b) A chemical test can be used to distinguish between separate samples of Isomer 1
and Isomer 2.

Identify a suitable reagent for the test.

State what you would observe with Isomer 1 and with Isomer 2.

Reagent ___________________________________________________________

Observation with Isomer 1 _____________________________________________

Page 27 of 87
___________________________________________________________________

Observation with Isomer 2 _____________________________________________

___________________________________________________________________
(3)

(i) State the infrared absorption range that shows that Isomer 3 and Isomer 4
contain the same functional group.

______________________________________________________________

______________________________________________________________
(1)

(ii) State one way that the infrared spectrum of Isomer 3 is different from the
infrared spectrum of Isomer 4.

______________________________________________________________

______________________________________________________________
(1)

(d) Two alcohols are formed by the hydration of Isomer 4.

Draw the displayed formula for the alcohol formed that is oxidised readily by
acidified potassium dichromate(VI).

(1)

(e) Isomer 4 reacts with hydrogen bromide to give two structurally isomeric
bromoalkanes.

(i) Name and outline a mechanism for the reaction of Isomer 4 with hydrogen
bromide to give 2-bromo-2-methylbutane as the major product.

(CH3)2C = CHCH3 + HBr (CH3)2CBrCH2CH3

Name of mechanism ____________________________________________

Mechanism

Page 28 of 87
(5)

(ii) The minor product in this reaction mixture is 2-bromo-3-methylbutane.

Explain why this bromoalkane is formed as a minor product.

______________________________________________________________

______________________________________________________________
(2)

(f) Name and outline a mechanism for the following reaction to form Isomer 5.
State the role of the hydroxide ion in this reaction.

(CH3)2CBrCH2CH3 + KOH H2C = C(CH3)CH2CH3 + KBr + H2O

Name of mechanism __________________________________________________

Mechanism

Role of hydroxide ion _________________________________________________

(5)
(Total 21 marks)

Q28.
This question is about some isomers of C5H8O2

(a) Compound H is a cyclic ester that can be prepared as shown.

On the structure of H, two of the carbon atoms are labelled.

HOCH2CH2CH2CH2COCl + HCL

Page 29 of 87
H

(i) Name and outline a mechanism for this reaction.

Use Table C on the Data Sheet to give the 13C n.m.r. δ value for the carbon
atom labelled a and the δ value for the carbon atom labelled b.

______________________________________________________________

______________________________________________________________
(7)

(ii) HOCH2CH2CH2CH2COCl can also react to form a polyester in a mechanism

similar to that in part (i).

Draw the repeating unit of the polyester and name the type of polymerisation
involved.

______________________________________________________________

______________________________________________________________
(2)

(b) State how you could distinguish between compounds J and K by a simple test-tube

Page 30 of 87
reaction.

State how you could distinguish between J and K by giving the number of peaks in
the 1H n.m.r. spectrum of each compound.

J K

___________________________________________________________________

___________________________________________________________________
(5)

(c) Draw the structure of each of the following isomers of C5H8O2

Label each structure you draw with the correct letter L, M, N, P or Q.

L is methyl 2-methylpropenoate.

M is an ester that shows E-Z stereoisomerism.

N is a carboxylic acid with a branched carbon chain and does not show
stereoisomerism.

P is an optically active carboxylic acid.

Q is a cyclic compound that contains a ketone group and has only two peaks in its
1
H n.m.r. spectrum.

(5)
(Total 19 marks)

Q29.
(a) The hydrocarbon but-1-ene (C4H8) is a member of the homologous series of alkenes.

Page 31 of 87
But-1-ene has structural isomers.

(i) State the meaning of the term structural isomers.

______________________________________________________________

______________________________________________________________
(2)

(ii) Give the IUPAC name of the position isomer of but-1-ene.

______________________________________________________________
(1)

(iii) Give the IUPAC name of the chain isomer of but-1-ene.

______________________________________________________________
(1)

(iv) Draw the displayed formula of a functional group isomer of but-1-ene.

(1)

(b) But-1-ene burns in a limited supply of air to produce a solid and water only.

(i) Write an equation for this reaction.

______________________________________________________________
(1)

(ii) State one hazard associated with the solid product in part (b)(i).

______________________________________________________________
(1)

(c) One mole of compound Y is cracked to produce two moles of ethene, one mole of
but-1-ene and one mole of octane (C8H18) only.

(i) Deduce the molecular formula of Y.

______________________________________________________________
(1)

(ii) Other than cracking, give one common use of Y.

______________________________________________________________
(1)

(d) In cars fitted with catalytic converters, unburned octane reacts with nitrogen
monoxide to form carbon dioxide, water and nitrogen only.

(i) Write an equation for this reaction.

______________________________________________________________

Page 32 of 87
(1)

(ii) Identify a catalyst used in a catalytic converter.

______________________________________________________________
(1)
(Total 11 marks)

Q30.
Compound X is shown below. It is a member of a homologous series of hydrocarbons.

(a) (i) Deduce the general formula of the homologous series that contains X.

______________________________________________________________
(1)

(ii) Name a process used to obtain a sample of X from a mixture containing other
members of the same homologous series.

______________________________________________________________
(1)

(b) There are several isomers of X.

(i) Give the IUPAC name of the position isomer of X.

______________________________________________________________
(1)

(ii) Draw the structure of a functional group isomer of X.

(1)

(c) At high temperatures, one molecule of C15H32 can be converted into two molecules of
X and one molecule of another compound.

(i) Write an equation for this reaction.

______________________________________________________________
(1)

(ii) State the name of the process used to obtain a high yield of X from C15H 32

Give one reason why this process is used in industry.

Page 33 of 87
Name _________________________________________________________

Reason _______________________________________________________

______________________________________________________________
(2)

(iii) State why high temperatures are needed for this process.

______________________________________________________________

______________________________________________________________
(1)

(d) Compound X can be converted into compound Y.

Compound Y is shown below.

(i) Suggest the formula of a reagent that could be added to X in order to convert it
into Y.

______________________________________________________________
(1)

(ii) Give one use of Y.

______________________________________________________________
(1)

(iii) Write an equation to show the reaction of Y in a limited supply of air to produce
a solid and water only.

______________________________________________________________
(1)

(iv) When a sample of Y, contaminated with CH SH, is burned completely in air, a

toxic gas is formed.

Identify this toxic gas and suggest a compound that could be used to remove
the toxic gas from the products of combustion.

Toxic gas ______________________________________________________

Compound used to remove toxic gas ________________________________

______________________________________________________________
(2)

(v) Suggest the name of the process that occurs when the toxic gas in part (d)(iv)
is removed.

______________________________________________________________

Page 34 of 87
(1)

(e) Explain why the boiling points of X and Y are similar.

___________________________________________________________________

___________________________________________________________________
(2)
(Total 16 marks)

Q31.
Hexane (C6H14) is a member of the homologous series of alkanes.

(a) (i) Name the raw material from which hexane is obtained.

______________________________________________________________
(1)

(ii) Name the process used to obtain hexane from this raw material.

______________________________________________________________
(1)

(b) C6H14 has structural isomers.

(i) Deduce the number of structural isomers with molecular formula C6H14

Write the number in this box.

(Space for working)

(1)

(ii) State one type of structural isomerism shown by the isomers of C6H14

______________________________________________________________
(1)

(i) Deduce the molecular formula of X.

______________________________________________________________

Page 35 of 87
______________________________________________________________
(1)

(ii) State the type of cracking that produces a high percentage of alkenes. State
the conditions needed for this type of cracking.

Type of cracking ________________________________________________

Conditions _____________________________________________________

______________________________________________________________
(2)

(iii) Explain the main economic reason why alkanes are cracked.

______________________________________________________________

______________________________________________________________
(1)

(d) Hexane can react with chlorine under certain conditions as shown in the following
equation.

C6H14 + Cl2 C6H13Cl + HCl

(i) Both the products are hazardous. The organic product would be labelled
‘flammable'.
Suggest the most suitable hazard warning for the other product.

______________________________________________________________
(1)

(ii) Calculate the percentage atom economy for the formation of C6H13Cl (Mr =
120.5) in this reaction.

______________________________________________________________

______________________________________________________________
(1)

(e) A different chlorinated compound is shown below. Name this compound and state
its empirical formula.

Name ____________________________________________________________

Empirical formula ___________________________________________________

(2)
(Total 12 marks)

Page 36 of 87
Q32.
Pentane is a member of the alkane homologous series.

(a) Give the general formula for the homologous series of alkanes.

___________________________________________________________________
(1)

(b) One of the structural isomers of pentane is 2,2-dimethylpropane.

Draw the displayed formula of 2,2-dimethylpropane.

State the type of structural isomerism shown.

___________________________________________________________________
(2)

(c) A molecule of hydrocarbon Y can be thermally cracked to form one molecule of

pentane and two molecules of ethene only.

Deduce the molecular formula of Y.

State why high temperatures are necessary for cracking reactions to occur.

Give one reason why thermal cracking reactions are carried out in industry.

___________________________________________________________________

___________________________________________________________________
(3)

(d) Write an equation for the incomplete combustion of pentane to form a solid
pollutant.

Suggest why this solid pollutant is an environmental problem.

Page 37 of 87
___________________________________________________________________

___________________________________________________________________

___________________________________________________________________
(2)

(e) Pentane can react with chlorine as shown in the following equation.

C5H12 + Cl2 → C5H11Cl + HCl

Calculate the percentage atom economy for the formation of C5H11Cl

Deduce how many straight-chain isomers of C5H11Cl could be formed.

___________________________________________________________________

___________________________________________________________________
(3)

(f) Consider the following compound.

Name this compound.

Deduce the empirical formula of this compound.

___________________________________________________________________

___________________________________________________________________
(2)
(Total 13 marks)

Page 38 of 87
Q33.
The table below shows the structures of three isomers with the molecular formula C 5H10O

Isomer 1

(E)-pent-3-en-2-ol

Isomer 2

pentanal

Isomer 3

(a) Complete the table by naming Isomer 3.

(1)

(b) State the type of structural isomerism shown by these three isomers.

___________________________________________________________________
(1)

(c) The compound (Z)-pent-3-en-2-ol is a stereoisomer of (E)-pent-3-en-2-ol.

(i) Draw the structure of (Z)-pent-3-en-2-ol.

(1)

(ii) Identify the feature of the double bond in (E)-pent-3-en-2-ol and that in
(Z)-pent-3-en-2-ol that causes these two compounds to be stereoisomers.

______________________________________________________________
(1)

(d) A chemical test can be used to distinguish between separate samples of Isomer 2
and Isomer 3.

Page 39 of 87
Identify a suitable reagent for the test.
State what you would observe with Isomer 2 and with Isomer 3.

Test reagent
_________________________________________________________

Observation with Isomer 2

______________________________________________

___________________________________________________________________

Observation with Isomer 3

______________________________________________

___________________________________________________________________
(3)

(e) The following is the infrared spectrum of one of the isomers 1, 2 or 3.

(i) Deduce which of the isomers (1, 2 or 3) would give this infrared spectrum. You
may find it helpful to refer to Table 1 on the Data Sheet.

______________________________________________________________
(1)

(ii) Identify two features of the infrared spectrum that support your deduction.
In each case, identify the functional group responsible.

Feature 1 and functional group _____________________________________

______________________________________________________________

Feature 2 and functional group _____________________________________

______________________________________________________________

Page 40 of 87
______________________________________________________________
(2)
(Total 10 marks)

Q34.
Pent-1-ene is a member of the alkene homologous series.

(a) Pent-1-ene can be separated from other alkenes.

State the physical property of alkenes that allows them to be separated from a
mixture by fractional distillation.

___________________________________________________________________
(1)

(b) (i) State the meaning of the term structural isomerism.

______________________________________________________________

______________________________________________________________
(2)

(ii) Name the branched chain isomer of pent-1-ene shown below.

______________________________________________________________
(1)

(iii) Draw the structure of a functional group isomer of pent-1-ene.

(1)

(c) The cracking of one molecule of compound X produces pent-1-ene, ethene and
butane in a 1:2:1 mol ratio.
Deduce the molecular formula of X and state a use for the ethene formed.

Molecular formula of X ________________________________________________

Page 41 of 87
___________________________________________________________________

Use of ethene _______________________________________________________

(2)
(Total 7 marks)

Q35.
Octane is the eighth member of the alkane homologous series.

(a) State two characteristics of a homologous series.

___________________________________________________________________

___________________________________________________________________
(2)

(b) Name a process used to separate octane from a mixture containing several different
alkanes.

___________________________________________________________________

___________________________________________________________________
(1)

Give the meaning of the term structural isomerism.

Name this isomer and state its empirical formula.

___________________________________________________________________

___________________________________________________________________
(4)

(d) Suggest why the branched chain isomer shown above has a lower boiling point than
octane.

Page 42 of 87
___________________________________________________________________

___________________________________________________________________

___________________________________________________________________
(2)
(Total 9 marks)

Page 43 of 87
Mark schemes

Q1.
M1 C:H = 7.3 : 12.2 seen
Extended response: M1 is for working of some sort leading
to the formulae.
If C3H5 and C6H10 are both shown but it is not indicated which
formula is which; or the formulas are stated the wrong way
round, then allow 1 mark for M2 and M3 combined; if both
correct formulas are given with only one stated correctly to
be the empirical/molecular formula, then allow M2 and M3.
1

M2 (converting C:H 7.3 : 12.2 to 3:5)

to give empirical formula = C3H5
1

M3 molecular formula = C6H10

M4, 5 two possible structures of C6H10 (in any structural form)

cyclic compounds with 6/5/4/3-membered C ring with one double bond, e.g.

or any dienes with 6 C atoms,

or a molecule with a triple bond

M4 and M5 ignore names given in addition to structures
Credit M4 and M5 for correct names if no structures drawn
Apply list principle to structures in M4 and M5
2

M6 (electrophilic) addition
1
Alternative route to C6H10 that could gain credit
M1 82/12 gives/suggests 6 C atoms
M2 molecular formula = C6H10
M3 empirical formula = C3H5
Alternative route to C6H10 that could gain credit
M1 82 × 0.878 = 72, (72/12) = 6 C atoms
M2 molecular formula = C6H10
M3 empirical formula = C3H5
M6 penalise nucleophilic addition; ignore bromination
[6]

Q2.
C
[1]

Page 44 of 87
Q3.
(a) Aldehyde/propanal has dipole-dipole forces (between molecules)
If any ‘covalent bonds broken’ CE=0 for clip.
Ignore Van der Waal forces
M1

Alcohol/propan-1-ol AND Carboxylic acid/ propanoic acid have hydrogen bonding

(between molecules).
Ignore reference to energy
M2

The forces between the molecules in aldehyde are weaker (than those in alcohol
and acid so it will evaporate first.)
M3 only awarded following correct M1 OR M2
Allow converse for M3
M3

(b) Keep the temperature of the reaction mixture below the boiling point of propan-1-
ol/below 97 °C
Allow temperature in range 49-96 inclusive
Allow description of cooling the vessel
M1

Cool the distillate / collecting vessel

Ignore reference to oxidising agents
Penalise lid / sealed container
M2

(c) Add named carbonate/hydrogencarbonate OR magnesium to a sample of the

distillate.
Incorrect chemical CE=0
Allow formula (mark on for incorrect formula)
Allow blue litmus or correct named indicator
M1

Effervescence/fizz/bubbles would confirm presence of acid or converse

Blue litmus turns red confirms acid present or converse
Allow gas/CO2 produced which turns lime water cloudy OR
gas/H2 produced which burns with a squeaky pop
M2

(d) (Temperature difference = 15.1 °C)

If ∆T wrong – AE mark on otherwise can only award M2
If use 457 in M1, can only score M2

q = 150 × 4.18 × 15.1 or 9467.7 J or 9.4677kJ

amount ethanol burned = 0.457/46.0 = 9.93 × 10-3 mol

If use 457 in M2 can score 2 for - 0.953 kJ mol-1
M2

Heat change per mole = (M1/1000)/M2 = 952.99 kJ mol-1

∆H = – 953 kJ mol–1 must be 3sfs and must be negative

Page 45 of 87
(allow range -953 to -954)
BEWARE if they miss conversion to kJ and also miss
conversion to g, they get answer = - 953 which scores 1
+953 can score M1 and M2
Allow -950 or -960 for rounding to 2sf
M3

(e) Elimination
Penalise base elimination
M1

Mechanism : Either (E1)

M2 for protonation of alcohol, i.e. lp plus arrow to H+

or to H of H–O– in H2SO4 and from H-O bond to O
M3 for protonated alcohol plus arrow showing loss of
water
M4 for arrow showing loss of H+
From correct carbocation (E1)
wrong alcohol used / alkene formed loses M4
3

OR (E2)

M2 for protonation of alcohol, i.e. lp plus arrow to H+

or to H of H–O– in H2SO4 and from H-O bond to O

Page 46 of 87
M3 for protonated alcohol plus arrow showing loss of
water
M4 for arrow showing simultaneous loss of H+
wrong alcohol used / alkene formed loses M4
3

(f) E-pent-2-ene
Allow trans
M1

C=C bond cannot rotate and

Each carbon in the double bond has (2) different groups attached.
Allow (two) different groups on each/either side of the double
bond.
M2
[16]

Q4.
B
[1]

Q5.
(a)

Must be a skeletal structure

(b)

Must be a displayed structure

(c) Any correct structural representation of alkene with 4 C atoms, either:

but-1-ene or
but-2-ene or
methylpropene

allow butadiene
1
[3]

Page 47 of 87
Q6.
B
[1]

Q7.
D
[1]

Q8.
(a) Any two of these isomers

(b) Chain isomerism

Mark consequential to part (a)
1

(c) C6H14 + 6.5O2 ⟶ 6CO + 7H2O

M1 Product is CO or C
M2 Balanced equation
1

C6H14 + 3.5O2 6C + 7H2O

Allow equations containing CO2 as long as either C, CO or
both are also present
1

(d) Less energy given out by the fuel / engine is less powerful / less efficient / needs
to burn more fuel to get the same energy / increased costs due to need to use
more fuel
Do not allow answers linked to CO poisoning or incomplete
combustion
1
[5]

Q9.
C
[1]

Page 48 of 87
Q10.
A
[1]

Q11.
C
[1]

Q12.
(a) 3
1

(b) Chain.
1

(c)

One 3D enantiomer.
1
Second enantiomer correctly drawn as 3D mirror image of
first.
1

(d) Plane-polarised light.

Rotated in opposite directions.

(e) Elimination

Page 49 of 87
Extended response question

Mechanism (3 marks)

M2 arrow from lone pair on O to H+

M3 1st intermediate and arrow from C–O+H2 bond to O (with loss of H2O)

M4 2nd intermediate (carbocation) and arrow from C–H bond to C–C (with loss of
H+) to form C=C

M3 and M4 can be scored in one step (see alternative mechanism below).

If carbocation incorrect then answer cannot score maximum marks.

Explanation of formation of 3 alkenes

M5 loss of H+ from C (in carbocation) adjacent to +C (to which −OH was attached)

M6 From 1C−2C+–3C–4C leads to but-1-ene

M7 From 1C–2C+–3C–4C leads to but-2-ene

M8 But-2-ene formed as mixture of E-Z isomers

Page 50 of 87
Alternative mechanism

[14]

Q13.
(a) C9H10O
1

(b)

Position (isomerism).
Allow Positional.
1

(c) Electrophilic substitution

CH3COCl + AlCl3 ⟶ CH3CO+ + AlCl4−

Page 51 of 87
Mechanism 3 marks:
M1 arrow from circle or within it to C of CH3C+O (+ must be
on C of CH3C+O).
1
M2 for Intermediate (must be 4-isomer)
CH3CO must be correctly positioned and bonded to gain M2
horseshoe must not extend beyond C2 to C6 but can be
smaller
+ not too close to C1.
1
M3 arrow into hexagon unless Kekule
Loss of H+ (allow from incorrect isomer)
Allow M3 arrow independent of M2 structure
Ignore base removing H in M3.
Allow Kekule structures (which must be correct).
1
[8]

Q14.
(a)

(b)
1

(c) Stage 1: consider the groups joined to right hand carbon of the C=C bond
Extended response
Maximum of 5 marks for answers which do not show a
sustained line of reasoning which is coherent, relevant,
substantiated and logically structured.

Consider the atomic number of the atoms attached

M1 can be scored in stage 1 or stage 2
1

C has a higher atomic number than H, so CH2OH takes priority

Page 52 of 87
1

Stage 2: consider the groups joined to LH carbon of the C=C bond

Both groups contain C atoms, so consider atoms one bond further away
1

C, (H and H) from ethyl group has higher atomic number than H, (H and H)
from methyl group, so ethyl takes priority
1

Stage 3: conclusion

The highest priority groups, ethyl and CH2OH are on same side of the C=C
bond so the isomer is Z
Allow M5 for correct ECF conclusion using either or both
wrong priorities deduced in stages 1 and 2
1

The rest of the IUPAC name is 3-methylpent-2-en-1-ol

(d) Moles of maleic acid = 10.0 / 116.0 = 8.62 × 10–2

AND mass of organic product expected = (8.62 × 10–2) × 98.0 = 8.45 g

Or moles of organic product formed = 6.53 / 98.0 = 6.66 × 10–2

% yield = 100 × 6.53 / 8.45

OR = 100 × (6.66 × 10–2) / (8.62 × 10–2)

= 77.294 = 77.3%

AND statement that the student was NOT correct

1
[10]

Q15.
(a) (Compounds with the) same molecular formula but different structural / displayed /
skeletal formula
1

(b) (basic) elimination

Mechanism points:

Correct arrow from lone pair on :OH– to H on C adjacent to C–Br

Correct arrow from C–H bond to C–C

Correct arrow from C–Br bond to Br

Structure of chosen product

Page 53 of 87
1

[6]

Q16.
(a) Alkenes
1

Correctly drawn molecule of cyclobutane or methyl

cyclopropane, need not be displayed formula
1

(b) C6H14 (or correct alkane structure with 6 carbons)

Allow hexane or any other correctly named alkane with 6
carbons
1

(d) High pressure

Allow pressure ࣙ MPa
Mention of catalyst loses the mark
1

(e) This question is marked using levels of response. Refer to the Mark Scheme
Instructions for Examiners for guidance on how to mark this question.

Level 3

Page 54 of 87
All stages are covered and the explanation of each stage is generally correct
and virtually complete.

Answer communicates the whole process coherently and shows a logical

progression from stage 1 and stage 2 (in either order) to stage 3.
5–6 marks

Level 2

All stages are covered but the explanation of each stage may be incomplete or
may contain inaccuracies OR two stages are covered and the explanations
are generally correct and virtually complete.

Answer is mainly coherent and shows progression. Some steps in each stage
may be out of order and incomplete.
3–4 marks

Level 1

Two stages are covered but the explanation of each stage may be incomplete
or may contain inaccuracies, OR only one stage is covered but the
explanation is generally correct and virtually complete.

Answer includes isolated statements but these are not presented in a logical
order or show confused reasoning.
1–2 marks

Level 0

Insufficient correct chemistry to gain a mark.

0 marks
Indicative chemistry content
Stage 1: consider effect of higher temperature on yield
(Or vice versa for lower temperature)
• Le Chatelier’s principle predicts that equilibrium shifts to
oppose any increase in temperature
• Exothermic reaction, so equilibrium shifts in
endothermic direction / to the left
• So a Higher T will reduce yield
Stage 2: consider effect of higher temperature on rate
(Or vice versa for lower temperature)
• At higher temperature, more high energy molecules
• more collisions have E>Ea
• So rate of reaction increases / time to reach equilibrium
decreases
Stage 3: conclusion
Industrial conditions chosen to achieve (cost-effective)
balance of suitable yield at reasonable rate
[11]

Q17.
(a) 2,2,4-trimethylpentane
1

Page 55 of 87
(b) 5
1

(c) C20H42 C8H18 + 2C3H6 + 3C2H4

(d) Mainly alkenes formed

(e) 4 (monochloro isomers)

(f)

(g) C8H1735Cl = 96.0 + 17.0 + 35.0 = 148.0

and C8H1737Cl = 96.0 + 17.0 + 37.0 = 150.0
Both required
1

Mr of this C8H17Cl = 148.8

(h) = 2.05 : 2.56 : 2.05

Simplest ratio =

= 1 : 1.25 : 1
1

Whole number ratio (× 4) = 4 : 5 : 4

MF = C8H10Cl8
1
[12]

Q18.
B
[1]

Q19.

Page 56 of 87
C
[1]

Q20.
B
[1]

Q21.

(a)
Must show all 4 groups bonded to C=C
Allow CH3− for methyl group; allow C2H5 for ethyl group
Allow correct structure of the style

Allow correct skeletal structure

(b) M1 electrophilic addition

NB the arrows here are double-headed

M2 must show an arrow from the double bond towards the

H atom of the H-Br molecule
1

M3 must show the breaking of the H-Br bond

M4 is for the structure of the tertiary carbocation

Page 57 of 87
M5 must show an arrow from the lone pair of electrons on
the negatively charged bromide ion towards the
positively charged atom (of either a secondary or) of a
tertiary carbocation
1

M6 3-bromo-3-methylpentane is formed from 3y carbocation

OR
2-bromo-3-methylpentane is formed from 2y carbocation
1

M7 3y carbocation more stable than 2y

1
M2-M5 Penalise one mark from their total if half-headed
arrows are used
M2 Ignore partial negative charge on the double bond
M3 Penalise incorrect partial charges on H-Br bond and
penalise formal charges
Penalise M4 if there is a bond drawn to the positive charge
Penalise only once in any part of the mechanism for a line
and two dots to show a bond
Max 3 of any 4 marks (M2-5) for wrong organic reactant or
wrong organic product (if shown) or secondary carbocation
Max 2 of any 4 marks in the mechanism for use of
bromine
Do not penalise the “correct” use of “sticks”
For M5, credit attack on a partially positively charged
carbocation structure but penalise M4
M6 is high demand and must refer to product being
formed from/via correct class of carbocation
M7 is high demand and must be clear answer refers to
stability of carbocations (intermediates) not products
Candidate that states that products are carbocations
would lose M6 and M7
M6,7 allow carbonium ion in place of carbocation; or a
description of carbocation in terms of alkyl groups/ number
of carbon atoms joined to a positive C

When asked to outline a mechanism, candidates are

expected to draw a mechanism with curly arrows
(specification 3.3.1.2). On this occasion only we would allow
a detailed description as shown.
M2 must describe the movement of a pair of electrons / curly
arrow from the C=C towards the H atom of the H-Br
molecule
M3 must describe the breaking of the H-Br bond with the
bonding pair of electrons moving to the Br / curly arrow from
H-Br bond to Br
M4 is for the structure of the tertiary carbocation (i.e. positive
C bonded to one methyl and two ethyl groups)
M5 must describe the movement of a pair of electrons from
the Br− ion to the positive C atom of the carbocation / curly
arrow from the lone pair of electrons on the negatively

Page 58 of 87
charged bromide ion towards the positively charged C atom
(of either a secondary or) of a tertiary carbocation
[8]

Q22.
B
[1]

Q23.
(a) (i) Alkane(s)
Ignore CnH2n+2
1

(ii) C8H18 + 12.5O2 → 8CO2 + 9H2O

Allow multiples
1

(iii) 2, 2, 4-trimethylpentane
1

(b) (i) But-1-ene

Ignore (E or Z)
1

(ii) C14H30
1

(iii) Thermal
If catalytic CE = 0
1

High pressure / 7000kPa / 70 atms

and
High temperature/temperature in range 400-1000°C (673–1273K)
(Allow ≥1000 kPa or ≥10 atms – no upper value)
Allow high temperature and pressure or high pressure and
temperature
If no units for temperature allow 673-1000
Must show unambiguous structure
Penalise lack of displayed formula once only
1

(iv)
1

Page 59 of 87
1

1
[10]

Q24.
(a) NaOH/KOH
IGNORE OH-
NOT M1 if any mention of acidified/H+ in reagents or
conditions
1

Reaction 1 = ethanolic/alcoholic AND reaction 2 = aqueous

IGNORE temp
NOT ethanoic
1

rxn 1 = base/proton acceptor

rxn 2 = nucleophile/lone pair donor/electron pair donor

(Base) Elimination
NOT nucleophilic
1

M6 must show an arrow from the lone pair on the oxygen of

a negatively charged hydroxide ion to a correct H atom

M7 must show an arrow from a correct C–H bond on C

adjacent to the C of the C–Br bond to a correct C–C bond.
Only award if an arrow is shown attacking the H atom of a
correct adjacent C–H bond in M6

M8 is independent provided it is from their original molecule

Page 60 of 87
and shows curly arrow from C-Br to Br
ALLOW correct E1 mechanism
IGNORE incorrect inorganic products
If forming pent-2-ene can award M8 only even if arrows in
mechanism correct
If C chain length or halogen wrong in reactant or product
max 2/3
1
1
1

(b)
1

1
If no M2 and M3 ALLOW 1 mark if both structures OR both
names correct
NOT cis and trans

No free rotation around C=C

ALLOW no rotation of C=C
1

2 different atoms/groups on each of the C=C Cs owtte

IGNORE ‘functional’
1

(c) Same volume/amount of AgNO3(aq) added to same

volume/amount/no. of drops of haloalkane (in beaker/flask)
in each experiment
Both volume references needed
IGNORE inappropriate volumes
1

Same temp OR same [AgNO3] each time

Page 61 of 87
record time to measure sensible observation about the
amount of AgCl ppt
e.g. first appearance of ppt / ppt obscures mark / reading on
a colorimeter
IGNORE colour of ppt
ALLOW silver mirror
NOT reference to same time if describing method based on
timing how long (for ppt to form)
ALLOW gravimetric method based on same time for each
experiment
1

Rate = amount/time OR proportional to 1/time OR reference

to shorter time = higher rate/longer time = lower rate
ALLOW greater mass = higher rate if gravimetric method
1
[17]

Q25.
(a) Saturated − single bonds only / no double bonds
1

Hydrocarbon − contains carbon and hydrogen (atoms) only

(b) C16H34 + 16.5O2 16CO + 17H2O

Allow multiples
1

(c) (On combustion) SO2 produced

Allow equation to produce SO2. Ignore sulfur oxides.
1

Which causes acid rain

If formula shown it must be correct
M2 is dependent on M1. But if M1 is sulfur oxides, allow M2.
For M2 allow consequence of acid rain or SO2.
Ignore greenhouse effect and toxic
1

(d) (i) C16H34 C8H18 + C2H4 + 2C3H6

Allow multiples
1

(ii) polypropene / propan(-1 or 2-)ol / propane(-1,2-)diol / isopropanol /

propanone / propanal
Accept alternative names
Ignore plastic and polymer
1

(iii)

Page 62 of 87
1

(e)

Allow any unambiguous representation

(f) 2,4-dichloro-2,4-dimethylhexane
Only but ignore punctuation
1
[10]

Q26.
(a) Crude oil OR petroleum
Not petrol.
1

Fractional distillation / fractionation

Not distillation alone.
1

(b) C12H26 + 12.5O2 12CO + 13H2O

Allow balanced equations that produce CO2 in addition to
CO.
Accept multiples.
1

(c) (i) M1 Nitrogen and oxygen (from air) react / combine / allow a correct
equation
If nitrogen from petrol / paraffin / impurities CE = 0 / 2.
1

M2 at high temperatures
Allow temperatures above 1000 °C or spark.
Not just heat or hot.
M2 dependent on M1.
But allow 1 mark for nitrogen and oxygen together at high
temperatures.
1

(ii) 2NO + O2 2NO2

Allow multiples.

Page 63 of 87
1

(iii) 4NO2 + 2H2O + O2 4HNO3

Allow multiples.
1

(d) (i) CnH2n+2

Allow CxH2x+2

CnH2n+2
Allow CxH2x+2
1

(ii) C12H26 C6H14 + C6H12

Only.
1

C3 H7
Only.
1

Zeolite / aluminosilicate(s)
Ignore aluminium oxide.
1

(iii) Larger molecule / longer carbon chain / more electrons / larger surface
area
1

More / stronger van der Waals’ forces between molecules

Allow dispersion forces / London forces / temporary induced
dipole-dipole forces between molecules.
If breaking bonds, CE = 0 / 2.
1

(e) 2,2,3,3,4,4-hexamethylhexane
Only.
Ignore punctuation.
1

Chain
Ignore branch(ed).
1

(f) Cl2
Only.

Cl–Cl
Not CL2 or Cl2 or CL2 or Cl2 or CL2.
Ignore Chlorine.
1
[16]

Q27.
(a) (i) M1 (Compounds / molecules with) the same structural formula

Page 64 of 87
Penalise M1 if ‘same structure’ or ‘different structural /
displayed formula’.

M2 with atoms / bonds / groups arranged differently in space

OR atoms / bonds / groups with different spatial arrangements / different

orientation
Ignore references to ‘same molecular formula’ or ‘same
empirical formula’.
Mark independently.
2

(ii)

Credit C–H3C
Credit C2H5
Penalise C–CH3CH2
1

(b) M1 Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent)

If M1, has no reagent or an incorrect reagent, CE=0.
Ignore ‘acidified’.

M2 Isomer 1: decolourised / goes colourless / loses its colour

For M1 penalise Br (or incorrect formula of other correct
reagent), but mark on.

M3 Isomer 2: remains orange / red / yellow / brown / the same OR no reaction

/ no (observable) change OR reference to colour going to the cyclopentane
layer
For M1, it must be a whole reagent and / or correct formula.
If oxidation state given in name, it must be correct. If
‘manganate’ OR ‘manganate(IV)’ or incorrect formula,
penalise M1, but mark on.

Alternatives : potassium manganate(VII)

M1 KMnO4 in acid M2 colourless M3 purple

M1 KMnO4 in alkali / neutral M2 brown solid M3 purple

Credit for the use of iodine

M1 iodine (solution / in KI) M2 colourless M3 (brown) to purple (credit no

change)

Credit for the use of concentrated H2SO4

M1 concentrated H2SO4 M2 brown M3 no change / colourless

Ignore ‘goes clear’.
Ignore ‘nothing (happens)’.
Ignore ‘no observation’.
No credit for combustion observations.

Page 65 of 87
3

(c) (i) (Both infrared spectra show an absorption in range) 1620 to 1680 (cm−1)
Ignore reference to other ranges (eg for C–H or C–C).
1

(ii) The fingerprint (region) / below 1500 cm−1 will be different or its
fingerprinting will be different

different absorptions / peaks are seen (in the region) below 1500 cm−1
(or a specified region within the fingerprint range)
Allow the words ‘dip’ OR ‘spike’ OR ‘low transmittance’ as
alternatives for absorption.
QoL
1

(d)

All bonds must be drawn.

Ignore bond angles.
1

(e) (i) M1 Electrophilic addition

M1 both words needed.

Penalise one mark from their total if half-headed arrows are

used.

M2 must show an arrow from the double bond towards the H atom of the
H–Br molecule
M2 Ignore partial negative charge on the double bond.

M3 must show the breaking of the H–Br bond

M3 Penalise incorrect partial charges on H–Br bond and
penalise formal charges.

M4 is for the structure of the tertiary carbocation

Penalise M4 if there is a bond drawn to the positive charge.
Penalise once only in any part of the mechanism for a line

Page 66 of 87
and two dots to show a bond.

M5 must show an arrow from the lone pair of electrons on the negatively
charged bromide ion towards the positively charged carbon atom of
either a secondary or a tertiary carbocation
For M5, credit attack on a partially positively charged
carbocation structure but penalise M4.
Max 3 of any 4 marks in the mechanism for wrong organic
reactant or wrong organic product (if shown) or secondary
carbocation.
Max 2 of any 4 marks in the mechanism for use of
bromine.
Do not penalise the correct use of 'sticks”.

NB The arrows here are double-headed

(ii) M1 Reaction goes via intermediate carbocations / carbonium ions

M1 is a lower demand mark for knowledge that carbocations
are involved.

M2 (scores both marks and depends on M1)

Tertiary carbocation / carbonium ion is more stable (than the secondary

carbocation / carbonium ion)

Secondary carbocation / carbonium ion is less stable (than the tertiary

carbocation / carbonium ion)
M2 is of higher demand and requires the idea that the
secondary carbocation is less stable or the tertiary
carbocation is more stable. Reference to incorrect chemistry
is penalised.
A carbocation may be defined in terms of alkyl groups /
number of carbon atoms, rather than formally stated.
2

(f) M1 Elimination
M1 credit ‘base elimination’ but no other qualifying prefix.

Penalise one mark from their total if half-headed arrows are

used.

M2 must show an arrow from the lone pair on oxygen of a negatively charged
hydroxide ion to a correct H atom
Penalise M2 if covalent KOH

M3 must show an arrow from a correct C–H bond adjacent to the C–Br bond
to a correct C–C bond. Only award if an arrow is shown attacking the H atom

Page 67 of 87
of a correct adjacent C–H bond (in M2)

M4 is independent provided it is from their original molecule BUT penalise

M2, M3 and M4 if nucleophilic substitution shown

Award full marks for an E1 mechanism in which M2 is on the correct

carbocation

NB The arrows here are double-headed

Penalise M4 for formal charge on C or Br of the C–Br bond
or incorrect partial charges on C–Br.
Penalise M4 if an additional arrow is drawn from the Br of
the C–Br bond to, for example, K+.
Ignore other partial charges.
Penalise once only in any part of the mechanism for a line
and two dots to show a bond.
Max 2 of any 3 marks in the mechanism for wrong
reactant or wrong organic product (if shown) or a correct
mechanism that leads to the alkene 2-methylbut-2-ene.
Credit the correct use of “sticks” for the molecule except for
the C–H being attacked.

M5 hydroxide ion behaves as a base / proton acceptor / electron pair donor /

lone pair donor
Penalise M5 if ‘nucleophile’.
5
[21]

Q28.
(a) (i) (nucleophilic) addition-elimination
Not electrophilic addition-elimination
Ignore esterification
1

M3 for structure
• If wrong nucleophile used or O–H broken in first step,
can only score M2.
• M2 not allowed independent of M1, but allow M1 for
correct attack on C+
• + rather than δ+ on C=O loses M2.
• If Cl lost with C=O breaking lose M2.
• M3 for correct structure with charges but lone pair on
O is part of M4.
• Only allow M4 after correct / very close M3.

Page 68 of 87
• Ignore HCl shown as a product.
4

a 20-50 (ppm) or single value or range entirely within this range

If values not specified as a or b then assume first is a.
1

b 50-90 (ppm) or single value or range entirely within this range

(ii)

Must have trailing bonds, but ignore n.

OR –OCH2CH2CH2CH2CO– OR –CH2CH2CH2CH2COO–
Allow

but not - C4H8−

one unit only

Condensation
1

(b)

Tollens’ Fehling’s / Benedicts Acidified potassium

dichromate

Penalise wrong formula for Tollens or missing acid with

potassium dichromate but mark on.
1

J No reaction / no No reaction / no No reaction / no

(visible) change (visible) change (visible) change /
/ / stays
no silver mirror stays blue / no r orange / does not turn
ed green
ppt

Ignore ‘clear’, ‘nothing’.

Penalise wrong starting colour for dichromate.
1

K Silver mirror / Red ppt (orange) turns

grey ppt green
(allow brick red
or
red-orange)
1

Page 69 of 87
J Two (peaks)
Allow trough, peak, spike.
1

K Four (peaks)
Ignore details of splitting.
If values not specified as J or K then assume first is J.
1

(c) If all the structures are unlabelled, assume that the first drawn ester is L, the
second ester is M; the first drawn acid is N, the second P. The cyclic
compound should be obvious.

L
ester

OR H2C=C(CH3)COOCH3
All C5H8O2 L to P must have C=C.
Allow CH3−.
Allow -CO2CH3 etc.
Allow CH2C(CH3)COOCH3.
1

M
ester

CH3CH=CHCOOCH3 CH3CH=CHOOCCH3 CH3CH=C(CH3)OOCH

CH3CH=CHCH2OOCH CH3CH2CH=CHOOCH
Allow either E–Z isomer.
Allow CH3− or C2H5− but not CH2CH3−.
Allow CH3CHCHCOOCH3 etc.
1

N
acid

(CH3)2C=CHCOOH H2C=C(CH3)CH2COOH H2C=C(COOH)CH2C

Page 70 of 87
Allow CH3− or C2H5− but not CH2CH3−.
Allow −CO2H.
Not cyclic isomers.
Not the optically active isomer.

Allow (CH3)2CCHCOOH etc.

P
acid

Allow −CO2H.

CH3CH(COOH)CH=CH2
Allow CH3CH(CO2H)CHCH2 or
CH3CH(CO2H)C2H3.
1

Not cyclic esters.

1
[19]

Q29.
(a) (i) (Compounds with the) same molecular formula
Allow same number and type of atom for M1
Ignore same general formula.
1

But different structural formula / different displayed formula / different

structures / different skeletal formula
M2 dependent on M1
Not different positions of atoms / bonds in space.
1

(ii) But-2-ene
Allow but-2-ene.
Allow but 2 ene.
Ignore punctuation.
1

Page 71 of 87
(iii) (2)-methylprop-(1)-ene
Do not allow 2-methyleprop-1-ene.
1

(iv)

Do not allow skeletal formulae.

Penalise missing H and missing C
1

(b) (i) C4H8 + 2O2 → 4C + 4H2O

Accept multiples.
1

(ii) Exacerbates asthma / breathing problems / damages lungs / smog /

smoke / global dimming
Ignore toxic / pollutant / soot / carcinogen.
Do not allow greenhouse effect / global warming / acid rain /
ozone.
1

(c) (i) C16H34

Allow H34C16
C and H must be upper case.
1

(ii) Jet fuel / diesel / (motor) fuel / lubricant / petrochemicals / kerosene /

paraffin / central heating fuel / fuel oil
Ignore oil alone.
Not petrol / bitumen / wax / LPG / camping fuel.
1

(d) (i) C8H18 + 25NO → 8CO2 + 12.5 N2 + 9H2O

Accept multiples.
1

(ii) Ir / iridium

Pt / platinum

Page 72 of 87
OR

Pd / palladium

Rh / rhodium
1
[11]

Q30.
(a) (i) CnH2n / CxH2x
1

(ii) Fractional distillation / GLC / gas liquid chromatography / fractionation

Do not allow cracking / distillation
1

(b) (i) But-1-ene / but1ene

Ignore hyphens and commas
Do not allow butene-1 / but-2-ene / butane / butane /alkene /
C4H8 / propene / straight-chain alkene
1

(ii) A structure of cyclobutane or

methyl-cyclopropane
Allow skeletal formula.
1

(c) (i) C15H32 → 2C4H8 + C7H16

Do not accept multiples.
1

(ii) Thermal cracking

Not catalytic cracking or cracking.
1

To produce products that are in greater demand / more valuable / more

expensive / more profitable
The (unsaturated) alkene or the (unsaturated) molecule or X
produced can be polymerised or can be made into plastics.
Ignore more useful products.
1

(iii) Break (C–C or C–H) bonds

Allow to overcome the activation energy.
Allow to break the carbon chain.
Penalise breaking wrong bonds.
1

(d) (i) H2
Only.
1

(ii) Fuel / LPG

Page 73 of 87
Allow camping gas, lighter fuel, propellant, refrigerant,
cordless appliances.
Do not allow petrol or motor fuel.
Ignore natural gas.
1

(iii) C4H10 + 2.5O2 → 4C + 5H2O

Accept multiples.
1

(iv) SO2 / sulfur dioxide

If other sulfur oxides, mark on.
1

Calcium oxide / CaO / lime / quicklime

Allow CaCO3 / allow Ca(OH)2 or names.
Allow any solid base.
M2 dependent on M1.
Do not allow limewater.
1

(v) Neutralisation
Allow acid-base reaction.
Allow flue gas desulfurisation / FGD
1

(e) (Molecules) are similar sizes / have similar Mr / have similar number of electrons
Chemical error CE = 0/2 if breaking bonds.
Allow similar number of carbon and hydrogen atoms / similar
surface area / similar chain length.
Can accept same number of carbon atoms.
Do not accept same number of H atoms / same number of
bonds.
Ignore similar amount of bonds.
1

Similar van der Waals forces between molecules / similar intermolecular forces
(IMF)
Not similar incorrect IMF eg dipole-dipole
1
[16]

Q31.
(a) (i) Crude oil / oil / petroleum
Do not allow ‘petrol’
1

(ii) Fractional distillation / fractionation / fractionating

Not distillation alone
1

(b) (i) 5
Allow five / V

Page 74 of 87
1

(ii) Chain (isomerism)

Allow branched chain / chain branched / side chain
(isomerism)
Ignore position (isomerism)
Do not allow straight chain / geometric / branched / function
1

(c) (i) C12H26 / H26C12

Only
1

(ii) Thermal cracking

If not thermal cracking, CE = 0/2
If blank mark on
1

High temperature
Allow ‘high heat’ for ‘high temperature’

(400°C < T < 900°C) or (650 K < T < 1200 K)

Not ‘heat’ alone
If no T, units must be 650 – 900

and

High pressure (> 10 atm, > 1 MPa, >1000 kPa)

(iii) To produce substances which are (more) in demand / produce products with a
high value / products worth more
Ignore ‘to make more useful substances’
1

(d) (i) Corrosive or diagram to show this hazard symbol

Ignore irritant, acidic, toxic, harmful
1

(ii) ( 120.5 × 100)

(86 + 71 )

=76.75(%) or 76.8(%)
Allow answers > 3 sig figs
1

(e) 2,2-dichloro-3–methylpentane
Ignore punctuation
Any order
1

C3H6Cl
1
[12]

Page 75 of 87
Q32.
(a) Cn H2n+2
Allow x in place of n
1

(b)

Chain
Must show every bond
Allow branched chain
2

To break the (C-C and/or C-H) bonds

M2=0 if break C=C
1

To make products which are in greater demand / higher

value / make alkenes
Not more useful products
Allow specific answers relating to question
1

(d) C5H12 + 3O2 → 5C + 6H2O

Allow other balanced equations which give C and CO/CO2
1

Causes global dimming / exacerbates asthma / causes

breathing problems / makes visibility poor / smog
Apply list principle
Ignore causes cancer / toxic
1

(e) (x 100)
1

74.48%
Allow 74.5%
1

Page 76 of 87
3
Only
1

(f) 2,3-dichloro-3-methylpentane
Ignore punctuation
1

C3H6Cl
Only
1
[13]

Q33.
(a) Pentan-2-one
ONLY but ignore absence of hyphens
1

(b) Functional group (isomerism)

Both words needed
1

Award credit provided it is obvious that the candidate is

drawing the Z / cis isomer
The group needs to be CHOHCH3 but do not penalise poor
C–C bonds or absence of brackets around OH
Trigonal planar structure not essential
1

(ii) Restricted rotation (about the C=C)

No (free) rotation (about the C=C)

(d)
M1 Tollens’ (reagent) M1 Fehling’s (solution) / Benedict’s

(Credit ammoniacal silver nitrate (Penalise Cu2+(aq) or CuSO4 but

OR a description of making mark M2 and M3)
Tollens’)

(Do not credit Ag+, AgNO3 or

[Ag(NH3)2+] or “the silver mirror
test” on their own, but
mark M2 and M3)

M2 silver mirror M2 Red solid/precipitate

Page 77 of 87
OR black solid or black precipitate (Credit orange or brown solid)

M3 (stays) colourless M3 (stays) blue

OR OR

no (observed) change / no reaction no (observed) change / no reaction

If M1 is blank CE = 0, for the clip

Check the partial reagents listed and if M1 has a totally
incorrect reagent, CE = 0 for the clip
Allow the following alternatives
M1 (acidified) potassium dichromate(VI) (solution); mark on
from incomplete formulae or incorrect oxidation state
M2 (turns) green
M3 (stays) orange / no (observed) change / no reaction
OR
M1 (acidified) potassium manganate(VII) (solution);
mark on from incomplete formulae or incorrect oxidation
state
M2 (turns) colourless
M3 (stays) purple / no (observed) change / no reaction
In all cases for M3
Ignore “nothing (happens)”
Ignore “no observation”
3

(e) (i) Spectrum is for Isomer 1

or named or correctly identified

The explanation marks in (e)(ii) depend on correctly
identifying Isomer 1.
The identification should be unambiguous but candidates
should not be penalised for an imperfect or incomplete
name. They may say “the alcohol” or the “alkene” or the “E
isomer”
1

(ii) If Isomer 1 is correctly identified, award any two from

• (Strong / broad) absorption / peak in the range

3230 to 3550 cm–1 or specified value in this range
or marked correctly on spectrum
and
(characteristic absorption / peak for) OH group /alcohol group

• No absorption / peak in range 1680 to 1750 cm–1 or

absence marked correctly on spectrum
and
(No absorption / peak for a) C=O group / carbonyl group / carbon-
oxygen double bond

• Absorption / peak in the range 1620 to 1680 cm–1

Page 78 of 87
or specified value in this range or marked correctly
on spectrum
and

(characteristic absorption / peak for) C=C group

/ alkene / carbon-carbon double bond
If 6(e)(i) is incorrect or blank, CE=0
Allow the words “dip” OR “spike” OR “trough” OR “low
transmittance” as alternatives for absorption.
Ignore reference to other absorptions e.g. C-H, C-O
2
[10]

Q34.
(a) (Different) boiling points
Ignore mp’s, references to imf, different volatilities
1

(b) (i) Compound which have the same molecular formula

Accept same no and type of atom for M1
But If same (chemical) formula M1 = 0 but allow M2
If empirical formula CE = 0/2
1

but different structures/different structural

formulae/different displayed formulae
M2 dependent on M1
1

(ii) 3-methylbut-1-ene
only
ignore commas and hyphens
1

(iii)

Allow any correct structure with a cyclic alkane

Page 79 of 87
Do not allow

i.e with an H missing on one C

Making plastics/used to make polymers or polythene/used

to make antifreeze/make ethanol/ripening fruit/any named
additional polymer
not used as a plastic/polymer/antifreeze
not just ‘polymers’ – we need to see that they are being
made
1
[6]

Q35.
(a) • (Same) General formula/allow a named homologous series
with its general formula

• Chemically similar/same (chemical) reactions

• Same functional group

• Trend in physical properties/eg inc bp as Mr increases

• (Molecules) increase by CH2/Mr = 14

Any two points
2

(b) Fractional distillation/fractionation/chromatography

Allow GLC
1

(c) (Molecules/compounds/substances) with the same molecular

formula/same number and type of atoms
Allow alkanes with same molecular formula
Allow same chemical formula in M1 = 0 but can allow M2
1

Page 80 of 87
but different structural formula/different displayed formula/different
arrangement of atoms/different structures
Not different positions in space
1

2,4-dimethylhexane
M2 dependent on M1
1

C4 H9
Ignore the absence of dash and/or commas
1

(d) less surface contact/less surface area/less polarisable

molecule
1

so fewer/weaker/less Van der Waals’/vdw forces

Allow more spherical or fewer points of contact
Not smaller molecule/not more compact molecule/not shorter
chain
Allow converse arguments
Must be comparative answer ie not just few VDW forces
QoL
Assume ‘it’ refers to the branched isomer
1
[9]

Page 81 of 87
Examiner reports

Q1.
Some students could not convert the ratio 7.3 : 13.2 to a whole number ratio, but the
question was answered well on the whole and discriminated well.

Q2.
Few students (28.7%) got this correct, with most believing there are fewer isomers than
there actually are.

Q3.
(a) This question discriminated well: 28.3% of students correctly identified the types of
intermolecular forces and noted that hydrogen bonding in the alcohol and the acid
was stronger than dipole-dipole attractions between propanal molecules. Despite
the request in the question to consider intermolecular forces, a few students still
discussed the breaking of bonds in the molecules and so gained no marks, although
fewer did this than is often the case in this type of question.

(b) Very few students (4%) scored both marks in this question and only 39.2% scored
at least one mark, despite the question being based on one of the required practical
activities.

(c) This part was answered well by nearly two-thirds of the students. The main error
was to test for the aldehyde rather than the acid.

(d) This question discriminated well and there was a good spread of marks. Sadly,
some students did not quote their answers to three significant figures and/or
remember the negative sign for their exothermic enthalpy change of combustion.

(e) The major errors in the answers to this acid-catalysed elimination of water were
where students confused this mechanism with the elimination of HX from a
halogenoalkane using a base. However, just under a third of students scored full
marks in a correct mechanism, either via the formation of a carbocation or by
showing the simultaneous loss of water and H+ from a protonated alcohol.

(f) This part was challenging and a surprising proportion of students (8%) made no
attempt. A large number scored no marks as they discussed the formation of
different alkenes, rather than why pent-2-ene shows E-Z isomerism. Sadly, some of
those who did gain the first mark failed to gain the second as this required two
statements, not only that the C=C bond cannot rotate, but also that each carbon in
the double bond has two different groups attached to it.

Q4.
A was the commonest incorrect response to this question which had a 47% success rate.
This suggests there were many students who recognised that the answer is an aldehyde,
but who then missed a possible isomer. Drawing out possible structures in a logical
sequence is the key here. Students are advised to start with a 5C chain, then 4C and find
possible positions for the fifth C (carbon 2 or carbon 3), and finally a 3C chain and find
positions for the remaining two carbons (both on carbon 2).

Q5.

Page 82 of 87
(a) This straightforward question was not answered well. Many students drew 2-
methylbutanal rather than 3-methylbutanal, not appreciating that the C atom in the
aldehyde group is carbon-1.

(b) Many students drew the displayed structure of the correct product, thereby
demonstrating their understanding of the identity of the major product of this addition
reaction of hydrogen bromide to the alkene.

(c) Most students realised that thermal cracking produced an alkene.

Q6.
A minority of students (31.9%) scored this mark, with many incorrectly thinking there were
one more or one fewer isomers than there actually were. Students are encouraged to take
a systematic approach to deducing all possible structures.

Q21.
Electrophilic addition

Many students could draw the correct structure of the Z isomer in (a).

Many students did well on (b), but a significant number attempted to describe the curly
arrow mechanism in words rather than drawing it. The phrase “outline the mechanism”
has been used for many years and is explained in the specification to mean drawing a
curly arrow diagram. On this occasion, it was decided that credit could stem from an
accurate description in words but it was very hard for students to match the level of
precision in words that is demanded in the drawing, and so most students who described
the curly arrow diagrams did not score well at all. The final two marks were awarded for
an explanation of why more of one product was formed than another. The explanation
should refer to the relative stability of the two possible carbocation intermediates. Many
students were confused and thought that the products were the carbocations. To score
these marks, students had to be clear that carbocations are intermediates from which the
products are formed and not the products themselves.

Q23.
Most students answered part (a) extremely well. They recognised that octane is an alkane
and then correctly balanced an equation for its complete combustion. A number stated
8.5O2 in the equation having not taken into account that CO2 contains two oxygen atoms.
Most students could give the correct IUPAC names in (a)(iii) and (b)(i). The molecular
formula of the alkane produced in (b)(ii) was deduced well and the type of cracking and
conditions were mostly stated correctly. A number of students then gave zeolite catalyst
as a condition. The displayed formulae in part (b)(iv) were drawn accurately with many
students scoring full marks. For those who did not score full marks there was a good
attempt at the question with marks two and three being accessed by the majority of
students. A number of students did not always show the displayed formula or did not
deduce the chain isomer.

Q24.
The lack of structure in part (a) caused problems for some students and they needed to
be clearer in some cases whether they were referring to reaction 1 or reaction 2. The
mechanism was generally done well although showing attack by OH- at the wrong C-H
lost some marks. In part (b) very few students appreciated the need for two different
groups on each C of the C=C in addition to the lack of free rotation.

Page 83 of 87
In part (c) it was expected that an experiment based on a ‘disappearing cross’ approach
would be familiar to most students as would the general idea of a ‘fair test’. There were,
however, many elaborate and often unworkable methods suggested. There was also too
much emphasis on things such as ‘the same person observing’ or ‘the same stopwatch
being used’ instead of making suggestions to ensure that the only variable was the
identity of the chloroalkane and that other conditions should be kept constant such as
temperature, volumes of solutions and concentration of silver nitrate solution.

Q25.
Most students gave correct answers for part (a) although there were still some who did not
state that only carbon and hydrogen are present in a hydrocarbon. The equation in part
(b) was generally correct although some did have carbon dioxide as one of the two
products. In part (c) the majority of students scored the first mark but some just stated that
sulfur dioxide was toxic and failed to mention acid rain. A few students suggested that the
sulfur compounds themselves escaped into the atmosphere without any mention of
combustion. The equation in part (d)(i) was well done; the most common error was having
the correct products but then failing to balance the equation. Answers to part (d)(ii) were
poor with relatively few stating a correct substance made. Part (d)(iii) was answered by a
majority of students; the most common error was to draw propene rather than the
functional group isomer. The structure in part (c) was also well done by the majority of
students, although some students left out a hydrogen atom from the chain and could not
score the mark.

Q26.
Part (a) was very well answered but many students could not give a correct balanced
equation in part (b); some gave carbon as a gaseous product. Answers to part (c) were
mixed. Some were excellent and gave the correct answer and condition but far too many
thought that the nitrogen was from a nitrogen-containing impurity in the paraffin. Equations
given in part (c)(ii) were generally good but many students found writing the equation in
part (c)(iii) more difficult.

The general formula of the alkanes was well known in part (d)(i). Answers to part (d)(ii)
suggested that many students did not read the question carefully and so did not write
equations giving two molecules with equal numbers of carbon atoms. Due to this error, the
empirical formula was often incorrect. A range of catalysts was seen but many did know
the correct one. In part (d)(iii), far too many students thought that covalent bonds were
broken during melting. When students realise that the van der Waals forces are broken
they must state that these forces are between the molecules. In a few answers, students
referred to van der Waals bonds breaking and this is unclear. The IUPAC name in part (e)
proved difficult for many students, especially the numbers of the substituent groups. The
type of isomerism in part (e) was well known by most students; the most common
incorrect answer was positional isomerism.

Q27.
Fewer than a third of students scored both marks for the definition in part (a)(i), often
missing the requirement to state that stereoisomers are compounds with the same
structural formula. Part (b) was generally well answered with most students scoring all 3
marks. Part (c)(ii) required appreciation of the fingerprint region or some equivalent idea
and only about one-third of students scored this mark. The displayed formula in part (d)
caused the usual problems and few were able to score this mark. The mechanisms in
parts (e)(i) and (f) were the most discriminating questions on the paper, producing a good
spread of marks. Part (e)(ii) required an explanation involving the relative stability of
carbocations, with a low demand and a much higher demand mark and only the highest-
scoring students scored both marks. It was a surprise to see answers that referred to the

Page 84 of 87
‘Markownikoff rule’ without any explanation in terms of the stability of carbocations.

Q28.
The nucleophilic addition-elimination mechanism in part (a)(i) presented a real challenge
to many students, who were confused by the cyclic nature of the product, failed to identify
the correct nucleophile and suggested either separate nucleophiles such as H2O, CH3OH
and OH– or alternatively loss of the proton from the OH group before nucleophilic attack.
Most students gave the correct range for the carbon atom labelled b, but often the range
for the carbon atom labelled a was given as 160–185 as for a carbonyl carbon. In part (a)
(ii), the repeating unit for the polyester was answered well although some students gave
twice the repeating unit.

The distinguishing test in part (b) was well done, although a significant number of students
thought that substance K was an acid and wrongly suggested NaHCO3 or Na2CO3 to
distinguish between the compounds. It was common for students to fail to see the
symmetry of J and so to predict, incorrectly, three peaks in its proton n.m.r. spectrum.
Five peaks was a common incorrect answer for K, suggesting that students had misread
the question and given the 13C n.m.r. result.

Part (c) of this question proved to be very challenging and fewer than 10% of students
scored full marks. Isomer Q was found particularly difficult where many students omitted
one of the O atoms from their suggested structure. Other common errors included missing
the double bond in L, giving the structure of P as the structure of N (which suggests a
failure to recognise that optical isomerism is a form of stereoisomerism) or writing an
unbranched carbon chain for the acid N. Answers to part (c) were often very badly
presented, with a great deal of crossing out, duplication of answers and poor labelling of
structures.

Q29.
Most students answered part (a) well although there were a few who omitted the key word
‘molecular’ in molecular formula. Most students could give the correct IUPAC name in part
(a)(ii) but the name in part (a)(iii) was more problematic. Part (a)(iv) was reasonably well
done although some students showed a cyclobutane structure without showing the
displayed formula as asked for in the question. The solid product in part (b)(i) was often
given as CO or CO2 and hence the mark for the hazard could not be scored in part (b)(ii).
Many those who correctly gave C as the product, simply stated that it was a pollutant
without further qualification. Part (c)(i) was answered well as was part (c)(ii). Common
incorrect answers to part (c)(ii) were bitumen and plastics. The equation in part (d)(i) was
generally answered well although again there were a lot of students who gave the formula
of nitrogen gas as N. The catalyst in part (d)(ii) was usually correct with the most common
answer being platinum.

Q30.
Part (a) was done well but part (b) proved more difficult for some students. Many simply
named the isomer given in part (b)(i) and few knew of the existence of cyclic alkanes in
part (b)(ii). Part (c) produced many careless responses; students should know that all
equations should be balanced. The type of cracking was not always specified in part (c)(ii)
and many students referred to the usefulness of the products rather than to their value. It
should be noted that cracking does not produce plastics; it produces alkenes that can be
polymerised. Answers to part (c)(iii) showed that some students think that intermolecular
forces are the only bonds broken in cracking. There were a vast number of incorrect
reagents stated in part (d)(i) and many gave names rather than formulae as asked for in
the question. The equation in part (d)(iii) was often not balanced and many students
showed carbon monoxide as the solid product. There were many students who did not

Page 85 of 87
know the identity of the toxic gas in (d)(iv) and therefore did not know a chemical that
could remove it.

The answers to (d)(v) were very varied. Only the students that knew the answer to part (d)
(iv) could get this right. Answers to part (e) showed that many students thought that
boiling involved the breaking of covalent bonds.

Q31.
The majority of students knew the answers to parts (a)(i) and (a)(ii) although a common
wrong answer to part (a)(ii) was cracking. Deducing the number of structural isomers in
part (b)(i) caused problems for many students and several students showed a lot of
working but then did not write a number in the box as instructed in the question. The type
of structural isomerism in part (b)(ii) was well known but many wrong answers for the
molecular formula were seen in part (c)(i). Many students lost marks in part (c)(ii) by
identifying the wrong type of cracking. Even when thermal cracking was identified
correctly, some students lost a mark by not stating the full conditions.

Most students scored the mark in part (c)(iii) although a few still gave answers in terms of
usefulness rather than demand. Most students realised that the product in part (d)(i) was
corrosive although ‘acidic’ was often seen. The atom economy was well answered in part
(d)(ii) although weaker students did not give the correct number for the denominator or
forgot to multiply by 100. The name in part (e) proved difficult for students with many
omitting the numbers or giving the wrong numbers and many putting the chloro and
methyl in the wrong order. The empirical formula was generally answered better although
a lot of students just gave the molecular formula.

Q32.
The general formula of alkanes was well known although some candidates did not write
clearly and the subscripts were often very difficult to read. The displayed formula in part
(b) was generally well done although there are still many candidates who do not
understand what a displayed formula is. The type of structural isomerism was generally
well known.

The molecular formula in part (c) was generally well answered but many candidates could
not give a clear answer as to why cracking reactions occur. Many simply stated that ‘the
chain was broken’ with no reference to bonds breaking. There are still a considerable
number of candidates who do not understand the concept of ‘supply and demand’ as
applied to the fractions obtained from crude oil. In part (d) equations were often given with
no solid product and consequently these candidates could not state the environmental
problem. The percentage atom economy in part (e) was generally well attempted although
many candidates truncated their answers rather than rounding up. Candidates gave a
wide range of answers for the number of isomers. The expected answer of three was
often seen since there are three straight chain structural isomers of C5H11Cl. However,
there is also an optical isomer of one of the straight chain isomers and candidates
repeating this unit with knowledge of CHEM4 may have answered four and so this was
also allowed. In part (f) the naming of the organic compound discriminated well but there
are quite a number of candidates who did not know the difference between empirical and
molecular formula.

Q33.
This was a relatively high-scoring question, although the correct name was only given by
33% of the candidates in part (a). Infrared spectroscopy is an area which candidates are
finding very accessible and although 90% identified the correct isomer in part (e), only
51% were able to obtain both marks in part (e)(ii).

Page 86 of 87
Q34.
The idea of boiling point was generally well known although a few stated melting point as
being the property in part (a). The definition in (b)(i) was well done with only a few missing
the idea of isomers having the same molecular formula. The name in (b)(ii) proved difficult
for a large number of candidates and the idea of cyclic alkanes in (b)(iii) was only
achieved by the most able candidates. Part (c) was answered reasonably well although
many candidates thought that the ethene itself was used as a plastic rather than being
used to make plastics.

Q35.
The answers to part (a) were generally quite good although there were some candidates
who quoted ‘similar properties’ without reference to chemical or physical properties. Less
able candidates thought that members of the series had the same molecular or empirical
formulae. The most common incorrect answer in part (b) was cracking. Part (c) was not
well answered. A surprisingly high number of candidates did not know the correct
definition and many candidates could not give the name of the structure. Some candidates
did not seem to understand how to deduce the empirical formula and often quoted the
molecular formula instead. Very few candidates scored full marks in part (d). Many
candidates realised that there would be fewer van der Waals forces in the branched chain
isomer but found difficulty with the idea of less surface contact. A disappointing number of
answers referred to breaking the covalent bonds in the molecules.

Page 87 of 87

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