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2
For
Examiner’s
Use
Section A
Answer all the questions in the spaces provided.
1
(a) What is meant by the term standard electrode potential, SEP?
...........................................................................................................................................
...........................................................................................................................................
[2]
(b) Draw a fully labelled diagram of the apparatus you could use to measure the SEP of the
Fe3+ / Fe2+ electrode.
[5]
(c) The reaction between Fe3+ ions and I– ions is an equilibrium reaction.
2Fe3+(aq) + 2I–(aq)
(i) Use the Data Booklet to calculate the
2Fe2+(aq) + I2(aq)
for this reaction.
....................................................................................................................................
(ii) Hence state, with a reason, whether there will be more products or more reactants
at equilibrium.
....................................................................................................................................
....................................................................................................................................
(iii) Write the expression for Kc for this reaction, and state its units.
Kc =
units .................................................
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An experiment was carried out using solutions of Fe3+(aq) and I–(aq) of equal
concentrations. 100 cm3 of each solution were mixed together, and allowed to reach
equilibrium.
For
Examiner’s
Use
The concentrations at equilibrium of Fe3+(aq) and I2(aq) were as follows.
[Fe3+(aq)] = 2.0 × 10–4 mol dm–3
[I2(aq)]
= 1.0 × 10–2 mol dm–3
(iv) Use these data, together with the equation given in (c), to calculate the concentrations
of Fe2+(aq) and I–(aq) at equilibrium.
[Fe2+(aq)] = ............................... mol dm–3
[I–(aq)] = ............................... mol dm–3
(v) Calculate the Kc for this reaction.
Kc = ......................................................
[8]
[Total: 15]
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2
For
Examiner’s
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Ethyl ethanoate is hydrolysed slowly by water in the following acid-catalysed reaction.
H+
CH3CO2CH2CH3 + H2O
CH3CO2H + CH3CH2OH
The concentration of ethyl ethanoate was determined at regular time intervals as the reaction
progressed.
Two separate experiments were carried out, with different HCl concentrations.
The following graph shows the results of an experiment using [HCl ] = 0.1 mol dm–3.
0.20
0.18
0.16
0.14
0.12
[CH3CO2CH2CH3]
0.10
/ mol dm–3
0.08
0.06
0.04
0.02
0
0
20
40
60
80
100
120
time / min
(a) When the experiment was carried out using [HCl ] = 0.2 mol dm–3, the following results
were obtained.
time / min
[CH3CO2CH2CH3]
/ mol dm–3
0
0.200
10
0.160
25
0.115
50
0.067
75
0.038
100
0.022
125
0.013
(i) Plot these data on the axes above, and draw a line of best fit.
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(ii) Use one of the graphs to show that the reaction is first order with respect to
CH3CO2CH2CH3.
For
Examiner’s
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Show all your working, and show clearly any construction lines you draw on the
graphs.
(iii) Use the graphs to calculate the order of reaction with respect to HCl.
Show all your working, and show clearly any construction lines you draw on the
graphs.
(iv) Write the rate equation for this reaction, and calculate the value of the rate constant.
rate =
[7]
(b) (i) Why is it not possible to determine the order of reaction with respect to water in this
experiment?
....................................................................................................................................
....................................................................................................................................
(ii) Although [CH3CO2CH2CH3] decreases during each experiment, [HCl ] remains the
same as its initial value.
Why is this?
....................................................................................................................................
....................................................................................................................................
[2]
[Total: 9]
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3
For
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(a) (i) What is meant by the density of a substance?
....................................................................................................................................
(ii) Use data from the Data Booklet to explain why the density of iron is greater than that
of calcium.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
[3]
(b) In general, reactions of the compounds of transition elements can be classified under
one or more of the following headings.
acid-base
ligand exchange
precipitation
redox
Choose the most suitable heading to describe each of the following reactions, by placing
a tick () in the appropriate column in the table below.
Only one tick should be placed against each reaction.
reaction
acid-base
ligand
exchange
precipitation
redox
[Cu(H2O)6]2+ + 4NH3 → [Cu(NH3)4]2+ + 6H2O
[Cu(H2O)6]2+ + 4HCl → [CuCl 4]2– + 4H+ + 6H2O
2FeCl 2 + Cl 2 → 2FeCl 3
[Fe(H2O)6]2+ + 2OH– → Fe(OH)2 + 6H2O
2Fe(OH)2 + ½O2 + H2O → 2Fe(OH)3
CrO3 + 2HCl → CrO2Cl 2 + H2O
Cr(H2O)3(OH)3 + OH– → [Cr(H2O)2(OH)4]– + H2O
[Cr(OH)4]– + 1½H2O2 + OH– → CrO42– + 4H2O
[8]
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(c) Alloys of aluminium, titanium and vanadium are used in aerospace and marine equipment,
and in medicine.
For
Examiner’s
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When a powdered sample of one such alloy is heated with an excess of aqueous NaOH,
only the aluminium reacts, according to the following equation.
2Al (s) + 2OH–(aq) + 6H2O(l) → 2[Al (OH)4]–(aq) + 3H2(g)
Reacting 100 g of alloy in this way produced 8.0 dm3 of hydrogen, measured under room
conditions.
Calculate the percentage by mass of aluminium in the alloy.
percentage = ........................ %
[3]
[Total: 14]
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4
Because of the lack of reactivity of the nitrogen molecule, extreme conditions need to be used
to synthesise ammonia from nitrogen in the Haber process.
(a) Suggest an explanation for the lack of reactivity of the nitrogen molecule, N2.
...........................................................................................................................................
...........................................................................................................................................
[1]
(b) Under conditions of high temperature, nitrogen and oxygen react together to give oxides
of nitrogen.
(i) Write an equation for a possible reaction between nitrogen and oxygen.
....................................................................................................................................
(ii) State two situations, one natural and one as a result of human activities, in which
nitrogen and oxygen react together.
....................................................................................................................................
....................................................................................................................................
(iii) What is the main environmental effect of the presence of nitrogen oxides in the
atmosphere?
....................................................................................................................................
[4]
(c) Describe and explain how the basicities of ethylamine and phenylamine compare to that
of ammonia.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[4]
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9
For
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(d) Compound X is a useful intermediate in the synthesis of pharmaceuticals.
X can be synthesised from chloromethylbenzene according to the following scheme.
CH2Cl
CH2CN
step 1
CH2CO2H
step 2
step 3
step 4
W
T
step 5
CH2CH2NH
C
CH2
O
X
(i) What type of reaction is each of the following?
step 1 .........................................................................................................................
step 2 .........................................................................................................................
(ii) Suggest reagents and conditions for
step 1, ........................................................................................................................
step 2. ........................................................................................................................
(iii) Draw the structures of the intermediates T and W in the boxes above.
[6]
[Total: 15]
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5
(a) A series of experiments is carried out in which the reagent shown at the top of the column
of the table is mixed, in turn, with each of the reagents at the side.
Complete the following table by writing in each box the formula of any gas produced.
Write x in the box if no gas is produced.
The first column has been completed as an illustration.
OH
CO2H
OH
H2O
Na
H2
KOH(aq)
x
Na2CO3(aq)
x
[5]
(b) Compound C is responsible for the pleasant aroma of apples. It can be prepared from
phenol by the following 3-step synthesis.
O
OH
OH
OH
step
1
O
step
2
H 3C
C
CH3
CH3
step
3
H 3C
C
CH3
H3C
C
CH3
CH3
CH3
A
B
C
CH3
(i) The only by-product of step 1 is HCl. Suggest the reagent that was used to react
with phenol to produce compound A.
....................................................................................................................................
(ii) What type of reaction is occurring in step 2?
....................................................................................................................................
(iii) What reagents and conditions are required for step 3?
....................................................................................................................................
(iv) State the reagent and conditions needed to convert C back to B, the reverse of
step 3.
....................................................................................................................................
[5]
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11
(c) (i) Either compound A or compound B, or both, react with the following reagents.
For each reagent draw the structure of the organic product formed with A, and with
B. If no reaction occurs, write ‘no reaction’ in the relevant box.
reagent and conditions
product with A
For
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product with B
an excess of Br2(aq)
heat with HBr
pass vapour over
heated Al 2O3
heat with acidified K2Cr2O7
(ii) Choose one of the above reactions to enable you to distinguish between A and B.
State below the observations you would make with each compound.
reagent
observation with A
observation with B
[7]
[Total: 17]
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For
Examiner’s
Use
Section B
Answer all the questions in the spaces provided.
6
There are two important polymerisations that occur within living organisms – protein synthesis
and the formation of DNA.
(a) Complete the table placing a tick () in the correct column to indicate in which process
each substance could be used.
substance
protein synthesis
formation of DNA
adenine
alanine
aspartate
phosphate
[3]
(b) Proteins and DNA form different helical structures. Briefly describe the bonding that
maintains the shape of each of these helical structures.
protein ...............................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
DNA ..................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[4]
(c) Describe the differences in bonding in the primary and tertiary structures of proteins.
Your answer should include reference both to the nature of the bonding and the types of
amino acid causing it.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[3]
[Total: 10]
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7
Modern methods of analysis have had far-reaching effects on a number of branches of
science including medicine, forensic science, environmental monitoring and archaeology.
For
Examiner’s
Use
(a) Outline, in simple terms, the technique of DNA fingerprinting.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[4]
(b) Complete the table by indicating whether the items can be used for DNA fingerprinting.
Use a tick () for items which can be used for DNA fingerprinting and a cross (x) for items
which cannot.
item for testing
suitable for DNA fingerprinting
human hair
piece of a flint tool
piece of Iron Age pot
piece of Roman leather
[3]
(c) Various forms of chromatography can be used to separate and analyse mixtures.
HPLC (high performance liquid chromatography) can be used to separate each of the
following mixtures. State another method of chromatography which would separate each
mixture.
insecticides in a sample of water ......................................................................................
dyes present in a foodstuff ...............................................................................................
drug residue in an athlete’s urine .....................................................................................
[3]
[Total: 10]
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8
In recent years there has been a lot of interest in polymers in the form of gels that absorb
aqueous materials. One of the largest uses of these polymers is in disposable nappies
(diapers). The gel which is used in this case is a polymer of propenoic acid.
O
OH
propenoic acid
(a) (i) Draw a section of the polymer of propenoic acid showing two repeat units.
(ii) By what type of chemical reaction is this polymer formed?
....................................................................................................................................
(iii) By what type of bonding is water held on the polymer?
....................................................................................................................................
[3]
(b) For some disposable nappies (diapers), the monomer is a mixture of propenoic acid and
sodium propenoate. The properties of the polymer are influenced by the proportion of
sodium salt in the monomer mixture.
(i) Suggest and explain how the difference in the structure of this polymer compared to
one formed only from propenoic acid might affect the water absorbing properties of
the polymer.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(ii) Suggest a property the polymer should have in order to be used in disposable
products.
....................................................................................................................................
[3]
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(c) A variation on the gel used for disposable nappies (diapers) containing more sodium
propenoate has been used to treat soils contaminated by heavy metals such as lead
(Pb2+) and cadmium (Cd2+). Suggest why the gel is effective.
For
Examiner’s
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...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[2]
(d) Another variation on this type of polymer is used in hair gels. In these, the polymer chains
are cross-linked by a compound known as pentaerythritol.
HO
OH
HO
OH
pentaerythritol
(i) By what type of chemical reaction are the cross-links in this polymer formed?
....................................................................................................................................
(ii) It is important that the gel should be easily washed out of hair. What is it about the
structure of the polymer that allows this to happen?
....................................................................................................................................
[2]
[Total: 10]
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For
Examiner’s
Use
Section A
Answer all the questions in the spaces provided.
1
A bromoalkane, R–Br, is hydrolysed by aqueous sodium hydroxide.
(a) (i) Write a balanced equation for this reaction.
....................................................................................................................................
(ii) What type of reaction is this?
....................................................................................................................................
[2]
(b) The concentration of bromoalkane was determined at regular time intervals as the
reaction progressed.
Two separate experiments were carried out, with different NaOH concentrations.
The graph below shows the results of an experiment using [NaOH] = 0.10 mol dm–3.
0.010
0.009
0.008
0.007
0.006
[R–Br]
0.005
/ mol dm–3
0.004
0.003
0.002
0.001
0
0
50
100
150
200
250
time / min
When the experiment was repeated using [NaOH] = 0.15 mol dm–3, the following results
were obtained.
time / min
[R–Br] / mol dm–3
0
40
80
120
160
200
240
0.0100
0.0070
0.0049
0.0034
0.0024
0.0017
0.0012
(i) Plot these data on the axes above, and draw a line of best fit.
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(ii) Use one of the graphs to confirm that the reaction is first order with respect to R–Br.
Show all your working, and show clearly any construction lines you draw.
For
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(iii) Use the graphs to calculate the order of reaction with respect to NaOH. Show all
your working, and show clearly any construction lines you draw on the graphs.
(iv) Write the rate equation for this reaction, and calculate the value of the rate constant.
rate =
[7]
(c) Nitric oxide, NO, and bromine vapour react together according to the following equation.
2NO(g) + Br2(g) → 2NOBr(g)
∆H = –23 kJ mol–1
The reaction has an activation energy of +5.4 kJ mol–1.
Use the following axes to sketch a fully-labelled reaction pathway diagram for this
reaction.
Include all numerical data on your diagram.
2NO + Br2
energy
/ kJ mol–1
extent of the reaction
[2]
[Total: 11]
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2
(a) (i) With the aid of a fully-labelled diagram, describe the standard hydrogen electrode.
(ii) Use the Data Booklet to calculate the standard cell potential for the reaction between
Cr2+ ions and Cr2O72– ions in acid solution, and construct a balanced equation for the
reaction.
= ......................... V
equation .....................................................................................................................
(iii) Describe what you would see if a blue solution of Cr2+ ions was added to an acidified
solution of Cr2O72– ions until reaction was complete.
....................................................................................................................................
....................................................................................................................................
[8]
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5
(b) A buffer solution is to be made using 1.00 mol dm–3 ethanoic acid, CH3CO2H, and
1.00 mol dm–3 sodium ethanoate, CH3CO2Na.
Calculate to the nearest 1 cm3 the volumes of each solution that would be required to
make 100 cm3 of a buffer solution with pH 5.50.
Clearly show all steps in your working.
Ka (CH3CO2H) = 1.79 × 10–5 mol dm–3
For
Examiner’s
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volume of 1.00 mol dm–3 CH3CO2H = ......................... cm3
volume of 1.00 mol dm–3 CH3CO2Na = ......................... cm3
[4]
(c) Write an equation to show the reaction of this buffer solution with each of the following.
(i) added HCl .................................................................................................................
(ii) added NaOH ..............................................................................................................
[2]
(d) Choose one reaction in organic chemistry that is catalysed by an acid, and write the
structural formulae of the reactants and products in the boxes below.
H+
[3]
[Total: 17]
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(a) Describe the reagents and conditions required to form a nitro compound from the
following.
CH3
(i)
methylbenzene
.......................................................
OH
(ii)
phenol
.......................................................
[3]
(b) Draw the structure of the intermediate organic ion formed during the nitration of benzene.
[1]
(c) In the box over the arrow below, write the reagents needed to convert nitrobenzene into
phenylamine.
NO2
NH2
[1]
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For
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(d) Phenylamine can be converted into the organic compounds A and B.
(i) Suggest the structural formulae of A and B in the boxes below.
(ii) Suggest suitable reagents and conditions for step 1, and write them in the box over
the arrow.
N
NH2
N
+
Cl –
step 1
O– Na+
Br2(aq)
A
B
[3]
(e) When phenylamine is treated with propanoyl chloride a white crystalline compound, C,
C9H11NO, is formed.
(i) Name the functional group formed in this reaction. ...................................................
(ii) Calculate the percentage by mass of nitrogen in C.
percentage = ........................ %
(iii) Draw the structural formula of C.
[3]
[Total: 11]
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(a) (i) Suggest why transition elements show variable oxidation states in their compounds
whereas s-block elements like calcium do not.
....................................................................................................................................
....................................................................................................................................
(ii) Calculate the oxidation number of the metal in each of the following ions.
VO2+
.......................................
CrF62–
.......................................
MnO42– .......................................
[4]
(b) Explain why transition element complexes are often coloured whereas compounds of
s-block elements such as calcium and sodium are not.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[4]
(c) SO2 and MnO4– react together in acidic solution.
(i) Use the Data Booklet to construct a balanced equation for this reaction.
....................................................................................................................................
(ii) Describe the colour change you would see when SO2(aq) is added to a sample of
acidified KMnO4 until the SO2 is in excess.
from ............................................................ to ........................................................
[3]
(d) Describe the observations you would make when NH3(aq) is added gradually to a solution
containing Cu2+ ions, until the NH3 is in an excess.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[3]
[Total: 14]
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9
5
For
Examiner’s
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Coffee beans contain chlorogenic acid.
OH
O
OH
OH
O
HO
O
OH
HO
chlorogenic acid
(a) (i) Draw circles around any chiral centres in the above structure.
(ii) Write down the molecular formula of chlorogenic acid.
....................................................................................................................................
(iii) How many moles of H2(g) will be evolved when 1 mol of chlorogenic acid reacts with
an excess of sodium metal?
....................................................................................................................................
(iv) How many moles of NaOH(aq) will react with 1 mol of chlorogenic acid under each
of the following conditions?
in the cold ...............................................
on heating ...............................................
[6]
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(b) On heating with dilute aqueous acid, chlorogenic acid produces two compounds, D and
E.
OH
chlorogenic acid
dil. H+(aq)
OH
OH
O
+
heat
HO
conc.
H2SO4
heat
OH
HO
OH
O
HO
D
E
Br2(aq)
in excess
C7H6O3
F
G
(i) What type of reaction is chlorogenic acid undergoing when D and E are formed?
....................................................................................................................................
When compound D is heated with concentrated H2SO4, compound F, C7H6O3, is formed.
Compound F evolves CO2(g) when treated with Na2CO3(aq), and decolourises Br2(aq),
giving a white precipitate. It does not, however, decolourise cold dilute acidified KMnO4.
When compound E is treated with an excess of Br2(aq), compound G is produced.
(ii) If the test with cold dilute acidified KMnO4 had been positive, which functional group
would this have shown to be present in F?
....................................................................................................................................
(iii) Name the functional groups in compound F that would react with the following.
Na2CO3(aq) ................................................. Br2(aq) .................................................
(iv) Suggest structures for compounds F and G and draw them in the relevant boxes
above.
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For
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(v) Compound E is one of a pair of stereoisomers.
What type of stereoisomerism is shown by compound E?
....................................................................................................................................
(vi) Draw the structure of the other stereoisomer in the box below.
[8]
(c) Calculate the volume of 0.1 mol dm–3 NaOH that is needed to react completely with 0.1 g
of compound E.
volume = ....................... cm3
[3]
[Total: 17]
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For
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Section B
Answer all the questions in the spaces provided.
6
There are two important polymerisations that occur within living organisms – protein synthesis
and the formation of DNA.
(a) Complete the table by placing a tick () in the correct column to indicate in which process
each substance could be used.
substance
protein synthesis
formation of DNA
cysteine
cytosine
glutamine
guanine
[3]
(b) DNA consists of a double helical structure.
(i) Describe the bonding between the two strands in DNA and state which part of each
strand is joined by it.
....................................................................................................................................
....................................................................................................................................
(ii) How does the strength of this bonding relate to the mechanism of the replication of
DNA?
....................................................................................................................................
....................................................................................................................................
[4]
(c) Some diseases are caused by changes in the structure of proteins. Explain the genetic
basis of these changes.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[3]
[Total: 10]
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7
The techniques of mass spectrometry and NMR spectroscopy are useful in determining the
structures of organic compounds.
(a) The three peaks of highest mass in the mass spectrum of organic compound L
correspond to masses of 142, 143 and 144.
The ratio of the heights of the M : M+1 peaks is 43.3 : 3.35, and the ratio of heights of
the M : M+2 peaks is 43.3 : 14.1.
(i) Use the data to calculate the number of carbon atoms present in L.
(ii) Explain what element is indicated by the M+2 peak.
....................................................................................................................................
....................................................................................................................................
Compound L reacts with sodium metal. The NMR spectrum of compound L is given
below.
2
1
4
9
8
7
6
5
4
δ / ppm
3
2
1
0
(iii) What does the NMR spectrum tell you about the number of protons in L and their
chemical environments?
....................................................................................................................................
....................................................................................................................................
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(iv) Use the information given and your answers to (i), (ii) and (iii) to deduce a structure
for L.
Explain how you arrive at your answer.
For
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structure of L
[7]
(b) The molecular formula C3H6 represents the compounds propene and cyclopropane.
H
C
H
CH3CH
CH2
H
C
H
propene
H
C
H
cyclopropane
(i) Suggest one difference in the fragmentation patterns of the mass spectra of these
compounds.
....................................................................................................................................
....................................................................................................................................
(ii) Suggest two differences in the NMR spectra of these compounds.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
[3]
[Total: 10]
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8
In recent years there has been considerable interest in a range of polymers known as
‘hydrogels’. These polymers are hydrophilic and can absorb large quantities of water.
(a) The diagram shows part of the structure of a hydrogel.
O
O
C
CH2
CH
CH2
CH
C
O
O
CH2
HO
CH2
C
CH2
OH
CH2
O
O
C
CH2
CH
CH2
CH
C
O
O
The hydrogel is formed from chains of one polymer which are cross-linked using another
molecule.
(i) Draw the structure of the monomer used in the polymer chains.
(ii) State the type of polymerisation used to form these chains.
....................................................................................................................................
....................................................................................................................................
(iii) Draw the structure of the molecule used to cross-link the polymer chains.
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17
(iv) During the cross-linking, a small molecule is formed as a by-product. Identify this
molecule.
For
Examiner’s
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....................................................................................................................................
[5]
(b) Once a hydrogel has absorbed water, it can be dried and re-used many times.
Explain why this is possible, referring to the structure on the opposite page.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[2]
(c) Not every available side chain in the polymer is cross-linked, and the amount of
cross-linking affects the properties of the hydrogel.
(i) The amount of cross-linking has little effect on the ability of the gel to absorb water.
Suggest why this is the case.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(ii) Suggest one property of the hydrogel that will change if more cross-linking takes
place. Explain how the increased cross-linking brings about this change.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
[3]
[Total: 10]
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Use
Section A
Answer all the questions in the spaces provided.
1
(a) Gaseous ammonia reacts with gaseous hydrogen chloride to form solid ammonium
chloride.
NH3 + HCl → NH4Cl
The bonding in ammonium chloride includes ionic, covalent and co-ordinate (dative
covalent) bonds.
Complete the following ‘dot-and-cross’ diagram of the bonding in ammonium chloride.
For each of the six atoms show all the electrons in its outer shell. Three electrons have
already been included.
Use the following code for your electrons.
● electrons from chlorine
x electrons from hydrogen
o electrons from nitrogen
+
H
x
–
H
●
o
N
H
Cl
H
[3]
(b) When a sample of dry ammonia is needed in the laboratory, the gas is passed through a
tower containing lumps of solid calcium oxide, CaO.
(i) Suggest why the usual drying agent for gases, concentrated H2SO4, is not used for
ammonia.
....................................................................................................................................
(ii) Write an equation for the reaction between CaO and H2O.
....................................................................................................................................
(iii) Suggest why CaO rather than MgO is used to dry ammonia.
....................................................................................................................................
[3]
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(c) (i) Write an equation showing the thermal decomposition of calcium nitrate, Ca(NO3)2.
For
Examiner’s
Use
....................................................................................................................................
(ii) State and explain how the thermal stabilities of the nitrates vary down Group II.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
[4]
[Total: 10]
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2
For
Examiner’s
Use
(a) The melting points of some Group IV elements are given below.
element
melting point / K
C
3925
Si
1683
Ge
1210
Sn
505
Suggest an explanation for each of the following.
(i) The melting point of silicon is less than that of carbon.
....................................................................................................................................
....................................................................................................................................
(ii) The melting point of tin is less than that of germanium.
....................................................................................................................................
....................................................................................................................................
[2]
(b) Using data from the Data Booklet where appropriate, write equations for the following
reactions of compounds of Group IV elements.
(i) SiCl 4(l) + H2O(l)
....................................................................................................................................
(ii) the action of heat on PbCl 4(l)
....................................................................................................................................
(iii) SnCl 2(aq) + FeCl 3(aq)
....................................................................................................................................
(iv) SnO2(s) + NaOH(aq)
....................................................................................................................................
[4]
[Total: 6]
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3
(a) (i) Using the symbol HZ to represent a Brønsted-Lowry acid, write equations which
show the following substances acting as Brønsted-Lowry bases.
NH3 +
→
CH3OH +
→
(ii) Using the symbol B– to represent a Brønsted-Lowry base, write equations which
show the following substances acting as Brønsted-Lowry acids.
NH3 +
→
CH3OH +
→
[4]
(b) State briefly what is meant by the following terms.
(i) reversible reaction
....................................................................................................................................
(ii) dynamic equilibrium
....................................................................................................................................
....................................................................................................................................
[2]
(c) (i) Explain what is meant by a buffer solution.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(ii) Explain how the working of a buffer solution relies on a reversible reaction involving
a Brønsted-Lowry acid such as HZ and a Brønsted-Lowry base such as Z–.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
[4]
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7
For
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(d) Propanoic acid, CH3CH2CO2H, is a weak acid with Ka = 1.34 × 10–5 mol dm–3.
(i) Calculate the pH of a 0.500 mol dm–3 solution of propanoic acid.
Buffer solution F was prepared by adding 0.0300 mol of sodium hydroxide to 100 cm3 of
a 0.500 mol dm–3 solution of propanoic acid.
(ii) Write an equation for the reaction between sodium hydroxide and propanoic acid.
....................................................................................................................................
(iii) Calculate the concentrations of propanoic acid and sodium propanoate in buffer
solution F.
[propanoic acid] = ................................ mol dm–3
[sodium propanoate] = ................................ mol dm–3
(iv) Calculate the pH of buffer solution F.
pH = ................................
[6]
(e) Phenyl propanoate cannot be made directly from propanoic acid and phenol.
Suggest the identities of the intermediate G, the reagent H and the by-product J in the
following reaction scheme.
ONa
O
H
CH3CH2CO2H
G
+
J
O
G is ..........................................................
H is ..........................................................
J is ..........................................................
[2]
[Total: 18]
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4
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(a) Explain what is meant by the term bond energy.
...........................................................................................................................................
...........................................................................................................................................
[2]
(b) (i) Describe and explain the trend in bond energies of the C–X bond in halogenoalkanes,
where X = F, Cl, Br or I.
....................................................................................................................................
....................................................................................................................................
(ii) Describe the relationship between the reactivity of halogenoalkanes, RX, and the
bond energies of the C–X bond.
....................................................................................................................................
....................................................................................................................................
[3]
(c) Use the Data Booklet to suggest an explanation as to why CFCs such as CF2Cl 2 are
much more harmful to the ozone layer than fluorocarbons such as CF4 or hydrocarbons
such as butane, C4H10.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[3]
(d) Predict the products of the following reactions and draw their structures in the boxes
below. The molecular formula of each product is given, where X = Cl , Br or I.
H 2O
+
Cl
Cl
C3H5O2X
O
H 2O
+
I
Cl
C3H7OX
Br
H 2O
+
Br
C7H7OX
[3]
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For
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(e) Ethane reacts with chlorine according to the following equation.
C2H6 + Cl 2 → C2H5Cl + HCl
(i) State the conditions needed for this reaction.
....................................................................................................................................
(ii) State the type of reaction occurring here.
....................................................................................................................................
One of the steps during this reaction is the following process.
Cl ● + CH3CH3 → HCl + CH3CH2●
(iii) Use the Data Booklet to calculate the enthalpy change, ∆H, of this step.
∆H = ................................ kJ mol–1
(iv) Use the Data Booklet to calculate the enthalpy change, ∆H, of the similar reaction:
I● + CH3CH3 → HI + CH3CH2●
∆H = ................................ kJ mol–1
(v) Hence suggest why it is not possible to make iodoethane by reacting together iodine
and ethane.
....................................................................................................................................
(vi) Complete the following equations of some possible steps in the formation of
chloroethane.
Cl 2 → ..............
Cl ● + CH3CH3 → HCl + CH3CH2●
CH3CH2● + .............. → ........................ + ..............
.............. + .............. → CH3CH2Cl
[8]
[Total: 19]
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5
Super-absorbent polymers have the ability to absorb 200-300 times their own mass of water.
They are classified as hydrogels and they are widely used in personal disposable hygiene
products such as babies’ nappies (diapers).
These polymers are commonly made by the polymerisation of compound K mixed with
sodium hydroxide in the presence of an initiator.
H
CH2
C
CO2H
K
(a) (i) Explain what is meant by the term polymerisation.
....................................................................................................................................
....................................................................................................................................
(ii) What type of polymerisation is involved in the formation of hydrogels?
....................................................................................................................................
(iii) Describe the changes in chemical bonding that occur during the polymerisation of K.
....................................................................................................................................
....................................................................................................................................
[3]
(b) Acrylic acid is the common name for compound K.
Suggest the systematic (chemical) name of K.
...........................................................................................................................................
[1]
(c) (i) Draw the structure of at least two repeat units of the polymer formed by the above
method from acrylic acid, K, when mixed with NaOH.
(ii) The C–C–C bond angle in compound K changes when the polymer is formed.
State and explain how the C–C–C bond angle differs between a molecule of K and
the polymer.
angle changes from ............................................ to .................................................
explanation ................................................................................................................
....................................................................................................................................
[4]
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11
(d) (i) Draw a detailed diagram of a portion of the polymer you have drawn in (c)(i) to
explain how it can absorb a large volume of water.
For
Examiner’s
Use
(ii) A student added 0.10 g of the polymer to 10 cm3 of aqueous copper(II) sulfate
solution.
Predict, with a reason, what you expect to observe.
....................................................................................................................................
....................................................................................................................................
[4]
(e) Compound L, CH2=CHCONH2, can also be polymerised to form a super-absorbent
polymer.
(i) Name the two functional groups in compound L.
....................................................................................................................................
....................................................................................................................................
Compound K can be converted into compound L by the following two-step route.
H
C
H 2C
H
C
step 1
CO2H
H2C
H
C
step 2
CO2 NH4+
H 2C
K
CONH2
L
(ii) Suggest a reagent for step 1.
....................................................................................................................................
(iii) What other product is formed in step 2?
....................................................................................................................................
(iv) State the reagents and conditions necessary to re-form K from L.
....................................................................................................................................
[5]
[Total: 17]
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For
Examiner’s
Use
Section B
Answer all the questions in the spaces provided.
6
(a) Protein molecules are formed by the polymerisation of amino acids in the body. The
structures of three amino acids are given.
O
OH
H 2N
O
glycine (gly)
HO
O
OH
NH2
serine (ser)
OH
NH2
valine (val)
(i) How many different tripeptides can be made using one molecule of each of the
amino acids shown?
....................................................................................................................................
(ii) Draw the tripeptide ser-gly-val, showing the peptide bonds in displayed form.
(iii) Within the tripeptide, which amino acid provides a hydrophobic side chain?
....................................................................................................................................
(iv) Polypeptide chains can form bonds giving proteins their secondary and tertiary
structures.
Using the tripeptide in (ii), state two types of bonding that can be formed and the
groups in the tripeptide that are involved in this bonding.
bond .................................................... groups ........................................................
bond .................................................... groups ........................................................
[6]
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(b) Enzymes are particular types of proteins that catalyse chemical reactions. The efficiency
of enzymes can be reduced by the presence of other molecules known as inhibitors.
Explain how both competitive and non-competitive inhibitors prevent enzymes from
working efficiently.
For
Examiner’s
Use
(i) competitive inhibitors .................................................................................................
....................................................................................................................................
....................................................................................................................................
(ii) non-competitive inhibitors ..........................................................................................
....................................................................................................................................
....................................................................................................................................
(iii) The graph shows the rate of an enzyme-catalysed reaction against the substrate
concentration in the absence of an inhibitor.
rate of
reaction
concentration of substrate
On the same axes, sketch a graph showing the rate of this reaction if a
non-competitive inhibitor was present.
[4]
[Total: 10]
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7
Electrophoresis is a technique which can be used to separate amino acids or peptide
fragments present in a mixture.
(a) Draw a diagram to show the apparatus used to carry out electrophoresis. You should
label each of the relevant parts of the apparatus.
[4]
(b) How far an amino acid will travel during electrophoresis depends on the pH of the solution.
For a given potential difference, state two other factors that will affect how far a given
amino acid travels in a fixed time during electrophoresis.
1. .......................................................................................................................................
...........................................................................................................................................
2. .......................................................................................................................................
...........................................................................................................................................
[2]
(c) A number of analytical and separation techniques rely on substances having different
partition coefficients.
State what is meant by the term partition coefficient.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[1]
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15
For
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(d) The partition coefficient of X between ethoxyethane and water is 40.0.
A solution contains 4.00 g of X dissolved in 0.500 dm3 of water.
Calculate the mass of X that can be extracted from this aqueous solution by shaking it
with
(i) 0.050 dm3 of ethoxyethane,
(ii) two successive portions of 0.025 dm3 of ethoxyethane.
[4]
[Total: 11]
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8
In a world with a rapidly increasing population, access to clean drinking water is critical. For
many countries, groundwater sources, rather than stored rainwater or river-water, are vital.
Groundwater is water that exists in the pore spaces and fractures in rock and sediment
beneath the Earth's surface. The World Health Organisation (WHO) provides maximum
recommended concentrations for different ions present in drinking water.
(a) The geological nature of the soil determines the chemical composition of the groundwater.
The table shows some ions which may contaminate groundwater.
ion present
WHO maximum permitted
concentration / mg dm–3
Ba2+
0.30
Cl –
250.00
NO3–
50.00
Pb2+
0.01
Na+
20.00
SO42–
500.00
(i) Nitrate, NO3–, ions are difficult to remove from groundwater.
What is the reason for this?
....................................................................................................................................
(ii) State which ions in the table above are likely to be removed from the water by
treatment with powdered limestone, CaCO3, giving reasons for each of your answers.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
[4]
(b) Nitrates and phosphates can enter water courses such as rivers or streams as a result
of human activity. Both of these ions are nutrients for algae.
(i) What is the origin of these nitrates?
....................................................................................................................................
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17
For
Examiner’s
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(ii) Suggest an origin for the phosphates found in water courses.
....................................................................................................................................
(iii) What effect do nitrates and phosphates have on water courses?
....................................................................................................................................
....................................................................................................................................
[3]
(c) Acid rain can have a major impact on natural waters, particularly lakes. In recent years
there has been a worldwide effort to reduce the amount of acid rain produced.
(i) Write equations to show the production of acid rain from sulfur dioxide, SO2.
....................................................................................................................................
....................................................................................................................................
(ii) The use of fossil fuels is one major source of sulfur dioxide.
Name another major industrial source.
....................................................................................................................................
[2]
[Total: 9]
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For
Examiner’s
Use
Section A
Answer all the questions in the spaces provided.
1
(a) The nitrate ion, NO3–, contains a dative covalent bond.
Complete the following ‘dot-and-cross’ diagram of the bonding in the nitrate ion. For
each of the four atoms show all the electrons in its outer shell. Three electrons have
already been included.
Use the following code for your electrons.
● electrons from oxygen
x electrons from nitrogen
□ added electron(s) responsible for the overall negative charge
–
O
x●
N
O
O
●
[3]
(b) (i) Write an equation showing the action of heat on magnesium nitrate, Mg(NO3)2.
....................................................................................................................................
(ii) Describe and explain the trend that is observed in the thermal stabilities of the
Group II nitrates.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
[4]
(c) When concentrated nitric acid, HNO3, is added to copper turnings, a brown gas is evolved.
Use data from the Data Booklet to construct an ionic equation for this reaction.
...........................................................................................................................................
...........................................................................................................................................
[2]
[Total: 9]
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2
For
Examiner’s
Use
(a) State two assumptions of the kinetic theory of gases, as applied to ideal gases.
...........................................................................................................................................
...........................................................................................................................................
[2]
(b) (i) State the conditions of temperature and pressure under which real gases behave
least like an ideal gas.
....................................................................................................................................
(ii) Explain why real gases do not behave ideally under these conditions.
....................................................................................................................................
....................................................................................................................................
[2]
(c) Gaseous aluminium chloride is dimeric at low temperatures, but the dimer dissociates on
heating.
Al 2Cl 6(g)
2Al Cl 3(g)
(i) State whether this dissociation is endothermic or exothermic. Explain your answer.
....................................................................................................................................
....................................................................................................................................
(ii) Choose one reaction in organic chemistry that is catalysed by Al Cl 3, and write the
structural formulae of the reactants and products in the boxes below.
Al Cl 3
[3]
[Total: 7]
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3
(a) Write equations, with state symbols, to define the following.
(i) the C–Br bond energy in CH3Br
....................................................................................................................................
(ii) the Al –Cl bond energy in Al Cl 3
....................................................................................................................................
[3]
(b) (i) Describe and explain the trend in bond energies of the bonds in Cl 2, Br2 and I2.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(ii) Fluorine, F2, does not follow this trend.
Suggest a possible reason why.
....................................................................................................................................
....................................................................................................................................
[3]
(c) (i) Use data from the Data Booklet to calculate the enthalpy change of the following
reaction.
H2(g) + X2(g) → 2HX(g)
when X = Cl
∆H = ........................ kJ mol–1
when X = I
∆H = ........................ kJ mol–1
(ii) Use these results to describe and explain the trend in the thermal stabilities of the
hydrides of Group VII.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
[5]
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5
(d) Bromine reacts with hot NaOH(aq) to give a solution which on cooling produces white
crystals of compound A.
A has the following percentage composition by mass: Na, 15.2; O, 31.8; Br, 53.0.
For
Examiner’s
Use
The remaining solution contains mostly NaBr, with a little of compound A.
(i) Calculate the empirical formula of A.
(ii) Construct an equation for the reaction between Br2 and hot NaOH(aq).
....................................................................................................................................
[4]
[Total: 15]
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4
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(a) The electrical conductivities of some Group IV elements are given below.
element
electrical
conductivity / Ω–1 cm–1
C (graphite)
6.1 × 102
Si
2.5 × 10–6
Ge
1.5 × 10–2
Sn
9.2 × 104
From a consideration of the structures, suggest reasons for the following.
(i) The electrical conductivity of silicon is less than that of graphite.
....................................................................................................................................
....................................................................................................................................
(ii) The electrical conductivity of tin is more than that of germanium.
....................................................................................................................................
....................................................................................................................................
[2]
(b) Using data from the Data Booklet where appropriate, write equations for the following
reactions of compounds of Group IV elements.
(i) the action of heat on PbO2(s)
....................................................................................................................................
(ii) PbO2(s) + HCl (aq)
....................................................................................................................................
(iii) SnO(s) + NaOH(aq)
....................................................................................................................................
(iv) GeCl 4(l) + H2O(l)
....................................................................................................................................
[4]
[Total: 6]
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5
(a) Bromine reacts with a variety of organic compounds.
For each of the following reactions,
●
complete and balance the equation, including the structural formula of the organic
product,
●
state the specific conditions (if any) under which the reaction takes place and the
type of reaction that occurs.
OH
(i) ............Br2 +
reaction conditions .....................................................................................................
type of reaction ..........................................................................................................
(ii) ............Br2 +
reaction conditions .....................................................................................................
type of reaction ..........................................................................................................
(iii) ............Br2 +
reaction conditions .....................................................................................................
type of reaction ..........................................................................................................
[10]
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9
(b) When hydrocarbon B is heated with concentrated manganate(VII) ions, three organic
compounds, C, D and E, are formed.
For
Examiner’s
Use
C
hot MnO4
D
B
E
(i) Suggest the identities of compounds C, D and E, drawing their structures in the
boxes above.
(ii) Use the relevant letter, C, D or E, to identify which of your compounds will react with
each of the following reagents.
Each reagent may react with more than one of C, D and E, in which case state all
the compounds that may react with each reagent.
●
2,4-dinitrophenylhydrazine ..............................
●
alkaline aqueous iodine ...................................
●
aqueous sodium hydroxide ..............................
[6]
[Total: 16]
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6
Naturally-occurring α-amino acids, RCH(NH2)CO2H, can be classified as amphiprotic
substances. An amphiprotic substance is one which can act as both a Brønsted-Lowry acid
and base.
α-amino acid
R group
alanine
CH3–
aspartic acid
HO2CCH2–
glycine
H–
lysine
H2N(CH2)4–
threonine
CH3CH(OH)–
serine
HOCH2–
(a) What is the Brønsted-Lowry definition of an acid?
...........................................................................................................................................
...........................................................................................................................................
[1]
(b) (i) All α-amino acids are soluble in water since they can form hydrogen bonds with
water molecules and can also exist as zwitterions.
Draw diagrams to show how the carboxylic acid and amino groups of alanine can
form hydrogen bonds with water molecules.
H
O
O
H
H
C
N
carboxylic acid
amino group
(ii) Draw the structure of the zwitterionic form of glycine.
[5]
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11
(c) The amino acid alanine can be formed by the reaction of CH3CHCl CO2H with an excess
of ammonia.
Outline a mechanism for this reaction using curly arrows.
For
Examiner’s
Use
[3]
(d) Amino acids can form different ions at different pH values.
Suggest the structures of the ions formed from the α-amino acids below at the respective
pH value.
lysine at pH 1
aspartic acid at pH 14
[2]
(e) (i) How many different dipeptides is it possible to synthesise, each containing two of
the three amino acids alanine, serine and lysine?
......................................
(ii) Write the structural formula of one of these dipeptides incorporating serine and
alanine.
[3]
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(f) Most naturally-occurring amino acids have a chiral centre and exhibit stereoisomerism.
(i) Define the term stereoisomerism.
....................................................................................................................................
....................................................................................................................................
There are four optical isomers of threonine.
Some of these optical isomers are drawn below.
H
HO2C
CH3
H2N
OH
H2N
OH
H
H
HO2C
F
HO2C
OH
H
H
H2N
H
H
H
G
CH3
H2N
CH3
CH3
HO2C
OH
J
H
When answering this question, remember that completely free rotation about a C–C
single bond occurs in these compounds.
(ii) Which of the structures G, H or J is identical to structure F? ....................................
(iii) The other two of the structures G, H or J represent two of the three other possible
optical isomers of threonine.
Complete the following partial structure of the fourth optical isomer.
H
CH3
[3]
[Total: 17]
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14
Section B
Answer all the questions in the spaces provided.
7
(a) Enzymes are particular types of proteins that catalyse chemical reactions. The efficiency
of enzymes can be reduced by the presence of other substances known as inhibitors.
(i) State one example of a substance that can act as a non-competitive inhibitor in
enzyme reactions.
....................................................................................................................................
(ii) For the inhibitor you have identified, explain why it is a non-competitive inhibitor.
....................................................................................................................................
....................................................................................................................................
(iii) The graph shows the rate of an enzyme-catalysed reaction against the substrate
concentration in the absence of an inhibitor.
rate of
reaction
concentration of substrate
On the same axes, sketch a graph showing the rate of this reaction if a competitive
inhibitor was present.
[4]
© UCLES 2013
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For
Examiner’s
Use
15
For
Examiner’s
Use
(b) DNA is responsible for encoding the amino acid sequence to produce proteins.
Ribosome, tRNA and mRNA are all involved in the process of protein synthesis.
(i) Write ribosome, tRNA and mRNA in the boxes below to show the correct sequence
in which they are involved.
DNA
protein
(ii) Sequences of three bases code for specific amino acids. The code UGA however
does not usually code for an amino acid. Suggest its use.
....................................................................................................................................
[3]
(c) Much of the energy used in biochemical reactions is provided by the hydrolysis of the
molecule ATP.
(i) What are the breakdown products of the hydrolysis of ATP?
....................................................................................................................................
(ii) Give two uses for the energy released by ATP hydrolysis in cells.
1. ................................................................................................................................
2. ................................................................................................................................
[3]
[Total: 10]
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8
Instrumental analysis plays an increasingly important role in modern chemistry. Two important
techniques are NMR spectroscopy and X-ray crystallography.
(a) Both techniques use part of the electromagnetic spectrum.
Which technique uses radiation with the longer wavelength, and in which part of the
spectrum is it found?
...........................................................................................................................................
[1]
(b) NMR spectroscopy provides detailed information about protons, but X-ray crystallography
is unable to detect them. Explain these facts.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[2]
(c) The protein found in hair contains the amino acid cysteine, C3H7SNO2. Crystalline
cysteine was examined using X-ray crystallography. State which atom produced the
strongest reflection, explaining your answer.
...........................................................................................................................................
...........................................................................................................................................
[1]
(d) Compound P is an alcohol that can be converted into compound Q in the following
reaction sequence.
P → CxH6O → Q
Spectral analyses of P and Q were carried out.
(i) The mass spectrum of P shows an M : M+1 peak ratio of 4.5 : 0.15.
Calculate the number of carbon atoms in P.
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Examiner’s
Use
17
For
Examiner’s
Use
The NMR spectra of P and Q are shown below.
P
11
10
9
8
7
6
5
δ / ppm
4
3
2
1
0
Q
12
10
8
6
δ / ppm
4
2
0
(ii) In the spectrum of P, clearly label the peak due to the –OH group with an X.
(iii) State how many different proton environments are present in compound Q.
......................................
(iv) What evidence is there in these spectra that P is a primary rather than a secondary
alcohol?
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(v) Draw a structure for Q.
[6]
[Total: 10]
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9
Until 1985, carbon was thought to exist in only two structural forms or allotropes. In 1985
another form, buckminsterfullerene, was discovered, in which the carbon exists as spherical
molecules.
(a) The other two forms of carbon have very different structures.
(i) Name these two forms.
.............................................................. and ..............................................................
(ii) Give three differences in physical properties between these two forms.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
[4]
(b) The diagram shows the structure of buckminsterfullerene.
buckminsterfullerene
The molecule of buckminsterfullerene contains 60 carbon atoms. Suggest a reason why
buckminsterfullerene reacts with hydrogen under suitable conditions and give a formula
for the product.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
[2]
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19
(c) In 2010, two scientists from the University of Manchester were awarded the Nobel Prize
for Physics for their work on graphene, a new structural form of carbon. Graphene
is one of the new ‘nano-materials’ being developed for commercial uses in the next
10 years.
graphene
(i) Graphene is in the form of sheets of carbon one atom thick. Calculate the number
of carbon atoms present in a sheet of graphene with a mass of one thousandth of a
gram (0.001 g).
The number of hexagons in a large sheet of graphene can be assumed to be one half of
the number of carbon atoms. Each hexagon has an area of 690 nm2.
(ii) Calculate the area of the sheet of graphene in (i).
area of sheet = .......................... nm2
(iii) Would you expect samples of graphene and buckminsterfullerene to be electrical
conductors? Explain your answers.
graphene ...................................................................................................................
....................................................................................................................................
buckminsterfullerene .................................................................................................
....................................................................................................................................
[4]
[Total: 10]
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2
Section A
Answer all the questions in the spaces provided.
1
(a) (i) State how the melting point and density of iron compare to those of calcium.
melting point of iron: ...........................................................................................................
density of iron: ....................................................................................................................
(ii) Explain why these differences occur.
melting point: ......................................................................................................................
.............................................................................................................................................
density: ...............................................................................................................................
.............................................................................................................................................
[4]
(b) The following diagram shows the apparatus used to measure the standard electrode potential,
E o, of a cell composed of a Cu(II) / Cu electrode and an Fe(II) / Fe electrode.
(i) Finish the diagram by adding components to show the complete circuit. Label the
components you add.
A
B
C
D
(ii) In the spaces below, identify or describe what the four letters A-D represent.
A .........................................................................................................................................
B .........................................................................................................................................
C .........................................................................................................................................
D .........................................................................................................................................
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(iii) Use the Data Booklet to calculate the E o for this cell.
.............................................................................................................................................
(iv) Predict how the size of the overall cell potential would change, if at all, as the concentration
of solution C is increased.
Explain your reasoning.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
[8]
(c) The iron(II) complex ferrous bisglycinate hydrochloride is sometimes prescribed, in capsule
form, to treat iron deficiency or anaemia.
A capsule containing 500 mg of this iron(II) complex was dissolved in dilute H2SO4 and titrated
with 0.0200 mol dm–3 KMnO4.
18.1 cm3 of KMnO4 solution were required to reach the end point.
The equation for the titration reaction is as follows.
5Fe2+ + MnO4– + 8H+  5Fe3+ + Mn2+ + 4H2O
(i) Describe how you would recognise the end point of this titration.
.............................................................................................................................................
(ii) Calculate
●
the number of moles of Fe2+ in the capsule,
●
the mass of iron in the capsule,
●
the molar mass of the iron(II) complex, assuming 1 mol of the complex contains 1 mol
of iron.
[4]
[Total: 16]
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2
The ions of transition elements form complexes by reacting with ligands.
(a) (i) State what is meant by the terms:
complex, .............................................................................................................................
.............................................................................................................................................
ligand. .................................................................................................................................
.............................................................................................................................................
(ii) Two of the complexes formed by copper are [Cu(H2O)6]2+ and CuCl 42–.
Draw three-dimensional diagrams of their structures in the boxes and name their shapes.
[Cu(H2O)6]2+
CuCl 42–
shape: ..............................................
shape: ..............................................
(iii) Platinum forms square-planar complexes, in which all four ligands lie in the same plane as
the Pt atom.
There are two isomeric complexes with the formula Pt(NH3)2Cl 2.
Suggest the structures of the two isomers, and, by comparison with a similar type of
isomerism in organic chemistry, suggest the type of isomerism shown here.
Structures of isomers:
isomer 1
isomer 2
Type of isomerism: .............................................................................................................
[7]
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(b) Copper forms two series of compounds, one containing copper(II) ions and the other containing
copper(I) ions.
(i) Complete the electronic structures of these ions.
Cu(II)
[Ar] ..................................................................................................................
Cu(I)
[Ar] ..................................................................................................................
(ii) Use these electronic structures to explain why
copper(II) salts are usually coloured,
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
copper(I) salts are usually white or colourless.
.............................................................................................................................................
.............................................................................................................................................
[5]
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(c) Copper(I) oxide and copper(II) oxide can both be used in the ceramic industry to give blue,
green or red tints to glasses, glazes and enamels.
values for some compounds.
The table lists the
compound
/ kJ mol–1
Cu2O(s)
–168.6
CuO(s)
–157.3
Cu(NO3)2(s)
–302.9
NO2(g)
+33.2
(i) Copper(II) oxide can be produced in a pure form by heating copper(II) nitrate. Use suitable
values from the table to calculate the H o for this reaction.
Cu(NO3)2(s)  CuO(s) + 2NO2(g) +
1
2
O2(g)
H o = ......................... kJ mol–1
(ii) Copper(I) oxide can be produced from copper(II) oxide.
●
Use suitable
values from the table to calculate H o for the reaction.
2CuO(s)
Cu2O(s) +
1
2
O2(g)
H o = ......................... kJ mol–1
●
Hence suggest whether a low or a high temperature of oxidation would favour the
production of copper(I) oxide. Explain your reasoning.
.............................................................................................................................................
.............................................................................................................................................
[4]
[Total: 16]
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3
Piperine is the compound responsible for the hot taste of black pepper.
O
O
N
O
piperine
Piperine is an amide and can be broken down as follows:
O
O
O
N
O
O
OH + HN
O
piperine
piperic acid
piperidine
(a) Suggest reagents and conditions for this reaction.
.............................................................................................................................................. [1]
(b) (i) How many stereoisomers are there with the same structural formula as piperic acid
(including piperic acid itself)?
.............................................................................................................................................
(ii) Draw the skeletal structure of a stereoisomer of piperic acid, different to the one shown
above.
(iii) Suggest structures for the compounds that would be formed when piperic acid is treated
with an excess of hot concentrated acidified KMnO4.
[4]
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(c) (i) Write the expression for Kw.
.............................................................................................................................................
(ii) Use your expression and the value of Kw in the Data Booklet to calculate the pH of
0.150 mol dm–3 NaOH(aq).
(iii) The pH of a 0.150 mol dm–3 solution of piperidine is 11.9.
HN
piperidine
Suggest why this answer differs from your answer in (c)(ii).
.............................................................................................................................................
.............................................................................................................................................
(iv) How would you expect the basicity of piperidine to compare to that of ammonia?
Explain your reasoning.
.............................................................................................................................................
.............................................................................................................................................
[5]
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(d) 20.0 cm3 of 0.100 mol dm–3 HCl was slowly added to a 10.0 cm3 sample of 0.150 mol dm–3
piperidine. The pH was measured throughout the addition.
(i) Calculate the number of moles of HCl remaining at the end of the addition.
moles of HCl = .....................
(ii) Hence calculate the [H+] and the pH at the end of the addition.
pH = .....................
(iii) On the following axes, sketch how the pH will change during the addition of a total of
20.0 cm3 of 0.100 mol dm–3 HCl. Mark clearly where the end point occurs.
14
pH
7
0
0
5
10
15
20
volume HCl added / cm3
(iv) From the following list of indicators, put a tick in the box by the side of the indicator most
suitable for this titration.
indicator
pH at which
colour changes
A
0-1
B
3-4
C
11 - 12
D
13 - 14
place one tick only
in this column
[6]
[Total: 16]
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4
Noradrenaline is a hormone and neurotransmitter, which is released during stress to stimulate the
heart and increase blood pressure.
OH
HO
NH2
HO
noradrenaline
(a) State the names of three functional groups in the noradrenaline molecule.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
(b) (i) Consider the following two-stage synthesis of noradrenaline from dihydroxybenzaldehyde.
H
HO
OH
O
step 1
step 2
HO
HO
NH2
HO
dihydroxybenzaldehyde
●
●
Z
noradrenaline
Draw the structure of the intermediate Z in the box.
Suggest reagents for steps 1 and 2.
step 1 ..................................................................................................................................
step 2 ..................................................................................................................................
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(ii) Dihydroxybenzaldehyde reacts with Br2(aq).
●
Describe what you would see during this reaction.
......................................................................................................................................
●
Draw the structure of the product.
[5]
(c) Draw the structures of the products when noradrenaline is reacted with
(i) dilute NaOH(aq),
(ii) dilute HCl (aq),
(iii) an excess of ethanoyl chloride, CH3COCl.
[4]
(d) Name the new functional groups formed in the reaction in (c)(iii).
....................................................................................................................................................
.............................................................................................................................................. [2]
[Total: 14]
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5
The two compounds V and W are isomers with the molecular formula C4H8O, and show the following
properties and reactions.
●
●
●
●
Both compounds react with sodium metal, and both decolourise bromine water.
Compound V forms a yellow precipitate with alkaline aqueous iodine, whereas compound
W does not.
When reacted with cold KMnO4(aq), both V and W produce the same neutral compound
X, C4H10O3.
Both V and W exist as pairs of stereoisomers.
(a) Suggest which functional groups are responsible for the reactions with
(i) sodium,
.............................................................................................................................................
(ii) bromine water,
.............................................................................................................................................
(iii) alkaline aqueous iodine.
.............................................................................................................................................
[3]
(b) Suggest structures for V and W.
V
W
[2]
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(c) State the type of stereoisomerism shown by compound V and draw the structures of the
stereoisomers.
type of stereoisomerism .............................................................................................................
structures of stereoisomers
isomer 1
isomer 2
[2]
(d) Suggest the structure of the neutral compound X.
X
[1]
[Total: 8]
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Section B
Answer all the questions in the spaces provided.
6
Proteins and deoxyribonucleic acid, DNA, are two important polymers that occur within living
organisms.
(a) Proteins have a number of ‘levels’ of bonding: primary, secondary and tertiary.
Complete the table to indicate the level of bonding responsible for the features described.
feature
level of bonding
formation of -helix
formation of disulfide bonds
formation of ionic bonds
linking amino acids
[3]
(b) The diagram shows part of a DNA molecule. Study the diagram and give the correct names for
the blocks labelled J, K, L and M.
J
guanine
K
M
adenine
L
block letter
name
J
K
L
M
[4]
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(c) The DNA molecule is formed from two polymer strands which are held together until DNA
replication occurs.
(i) What type of bonding holds the strands together?
.............................................................................................................................................
(ii) Explain why this type of bonding allows the base pairs within the strands to separate
during replication at normal body temperature.
.............................................................................................................................................
.............................................................................................................................................
[2]
(d) In the polymer RNA, the identities of two of the blocks, J, K, L or M, are different.
For one of these blocks that are different, give its correct name in DNA and in RNA.
DNA: ..........................................................................................................................................
RNA: ..........................................................................................................................................
[1]
[Total: 10]
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7
The combination of mass spectroscopy and NMR spectroscopy provides a powerful method of
analysis for organic compounds.
(a) The mass spectrum of a compound G contains M and M+1 peaks in the ratio of their heights
of 74 : 2.5.
Use these data to calculate the number of carbon atoms present in G. Show your working.
[2]
(b) The NMR spectrum of compound G is shown.
12
10
8
6
4
2
0
δ / ppm
(i) Use the Data Booklet and your knowledge of NMR spectroscopy to identify the type of
proton responsible for each of the three absorptions.
 / ppm
type of proton
1.1
2.2
11.8
(ii) The addition of D2O causes one of these absorptions to disappear.
Explain why this happens and state which absorption is affected.
.............................................................................................................................................
.............................................................................................................................................
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(iii) Draw the structural formula of G.
[6]
(c) Several structural isomers of G exist.
(i) Draw the structural formula of an isomer of G with only two absorptions in its NMR
spectrum.
(ii) Use the Data Booklet to suggest where these absorptions would occur.
peak
 / ppm
1
2
[3]
[Total: 11]
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8
(a) Many common drugs are taken orally, but some medications, such as those based on protein
molecules, are injected to prevent them being broken down in the digestive system.
(i) Name a functional group present in drug molecules that might be broken down by acid in
the stomach.
.............................................................................................................................................
(ii) State the type of reaction that would cause such a breakdown.
.............................................................................................................................................
(iii) Which one of the following compounds would not be suitable to be taken orally?
OH
O
CH3
HO
OCH3
O
CH3O
OH
N
CH3
H 3C
N
HO
OCH3
N
O
O
O
A
B
CH3
CH3
C
compound .......................
(iv) On the structure of your chosen compound in (iii), circle all the functional groups that
might be broken down by acid.
[5]
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(b) One way of protecting drug molecules that are taken orally is to enclose them in liposomes.
These are artificially created spheres made from phospholipids which have an ionic phosphate
‘head’ and two hydrocarbon ‘tails’.
P
Q
phospholipid
R
liposome
(i) State and explain in which location, P, Q or R, a hydrophobic drug could be carried.
.............................................................................................................................................
.............................................................................................................................................
(ii) By considering the nature of the functional groups in A, B and C, explain why these drugs
can be carried at position R in the liposome.
.............................................................................................................................................
.............................................................................................................................................
[2]
(c) Another method of protecting drug molecules is to ‘trap’ them inside gold nano-cages. When
they reach the site where they are needed, such as a tumour, the drug is released by exposing
the site to infra-red radiation.
(i) Suggest the size of the nano-cages in metres.
.............................................................................................................................................
(ii) Suggest why infra-red, rather than higher frequency radiation is used.
.............................................................................................................................................
.............................................................................................................................................
[2]
[Total: 9]
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Section A
Answer all the questions in the spaces provided.
1
(a) (i) On the diagrams below, show the outer electron arrangements of the atoms and ions
indicated. (Use the symbol  to represent a pair of electrons in an orbital.)
4s
4s
4s
3d
3d
3d
Fe
Fe2+(aq)
Zn2+(aq)
(ii) Use the above diagrams to explain why Fe2+(aq) ions are coloured, whereas Zn2+(aq) ions
are colourless.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
[4]
(b) When concentrated HCl is added to a solution of Cu2+(aq) ions, the solution turns yellow.
(i) State the formula of the species responsible for the yellow colour and name the type of
reaction that has occurred.
.............................................................................................................................................
.............................................................................................................................................
(ii) Ammonia can react as a base or as a ligand.
Describe the colour changes that occur when NH3(aq) is gradually added, with stirring, to
the yellow solution, until the NH3(aq) is in excess.
Identify the three ions or compounds responsible for the new colours.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
[7]
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(c) When aqueous solutions of KI and K2S2O8 are mixed almost no reaction occurs, but when a
few drops of Fe2+(aq) or Fe3+(aq) are added, iodine, I2(aq), is produced at a steady rate.
(i) Write an equation for the overall reaction.
.............................................................................................................................................
(ii) State the precise role of the iron ions during this reaction.
.............................................................................................................................................
(iii) By means of equations or otherwise, explain why the presence of either Fe2+ or Fe3+ is able
to speed up the reaction.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
[3]
[Total: 14]
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2
Lead(II) chloride, PbCl 2, can be used in the manufacture of some types of coloured glass.
PbCl 2 is only sparingly soluble in water. The [Pb2+] in a saturated solution of PbCl 2 can be estimated
by measuring the cell potential, Ecell, of the following cell.
A
H2(g)
1 atm, 298 K
salt bridge
B
D
saturated solution
of PbCl 2
C
solid PbCl 2
(a) In the spaces below, identify what the four letters A-D in the above diagram represent.
A .................................................................
B ................................................................
C .................................................................
D ................................................................
[4]
(b) In a saturated solution of PbCl 2, [PbCl 2(aq)] = 3.5  10–2 mol dm–3.
(i) The E o for the Pb2+ / Pb electrode is – 0.13 V. Predict the potential of the right-hand electrode
in the diagram above. Indicate this by placing a tick in the appropriate box in the table
below.
electrode
potential / V
place one tick only
in this column
– 0.17
– 0.13
– 0.09
0.00
Explain your answer.
.............................................................................................................................................
.............................................................................................................................................
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(ii) Write an expression for the solubility product, Ksp, of PbCl 2.
.............................................................................................................................................
(iii) Calculate the value of Ksp, including units.
Ksp = .......................................
units .......................................
[5]
(c) The behaviours of PbCl 2 and SnCl 2 towards reducing agents are similar, but their behaviours
towards oxidising agents are very different.
(i) Illustrate this comparison by quoting and comparing relevant E o values for the two metals
and their ions. Explain what the relative E o values mean in terms of the ease of oxidation
or reduction of these compounds.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(ii) Writing a balanced molecular or ionic equation in each case, suggest a reagent to carry
out each of the following reactions.
the reduction of PbCl 2
.............................................................................................................................................
the oxidation of SnCl 2
.............................................................................................................................................
[5]
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(d) (i) Write an equation to represent the lattice energy of PbCl 2. Show state symbols.
.............................................................................................................................................
(ii) Use the following data, together with appropriate data from the Data Booklet, to calculate
a value for the lattice energy of PbCl 2.
electron affinity of chlorine
enthalpy change of atomisation of lead
enthalpy change of formation of PbCl 2(s)
= –349 kJ mol–1
= +195 kJ mol–1
= –359 kJ mol–1
lattice energy = ............................. kJ mol–1
(iii) How might the lattice energy of PbCl 2 compare to that of PbBr2? Explain your answer.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
[6]
[Total: 20]
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3
The following four isomeric esters with the molecular formula C7H14O2 are used as artificial flavours
in drinks and sweets to give a pear, banana or plum taste to foodstuffs.
O
O
O
O
A
B
O
O
O
O
C
D
(a) In each of the spaces below, write one or more of the letters A-D, as appropriate.
(i) Which of these compounds can exist as optical isomers?
.............................................................................................................................................
(ii) On hydrolysis, which of these compounds produce(s) a secondary alcohol?
.............................................................................................................................................
[3]
(b) The hydrolysis of all these compounds produces ethanoic acid, CH3CO2H, as one of the
products.
State the reagents and conditions needed for this hydrolysis.
.............................................................................................................................................. [1]
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(c) The acid dissociation constant, Ka, of ethanoic acid is 1.75  10–5 mol dm–3.
(i) Explain why this value of Ka is
●
much larger than that of ethanol, CH3CH2OH,
.............................................................................................................................................
.............................................................................................................................................
●
smaller than that of chloroethanoic acid, Cl CH2CO2H.
.............................................................................................................................................
.............................................................................................................................................
(ii) Calculate the pH of a 0.100 mol dm–3 solution of ethanoic acid.
[4]
(d) 20.0 cm3 of 0.100 mol dm–3 NaOH were slowly added to a 10.0 cm3 sample of 0.100 mol dm–3
ethanoic acid, and the pH was measured throughout the addition.
(i) Calculate the number of moles of NaOH remaining at the end of the addition.
(ii) Calculate the [OH–] at the end of the addition.
(iii) Using the expression Kw = [H+][OH–] and your value in (ii), calculate [H+] and the pH of the
solution at the end of the addition.
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(iv) On the following axes, sketch how the pH will change during the addition of a total of
20.0 cm3 of 0.100 mol dm–3 NaOH. Mark clearly where the end point occurs.
14
pH
7
0
0
5
10
15
20
volume NaOH added / cm3
(v) From the following list of indicators, put a tick in the box by the side of the indicator you
consider most suitable for this titration.
indicator
pH at which
colour changes
malachite green
0-1
thymol blue
1-2
bromophenol blue
3-4
thymolphthalein
9 - 10
place one tick only
in this column
[7]
[Total: 15]
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4
Both ethene and benzene react with bromine.
H 2C
CH2
+
+
Br2
Br2
room
temperature
BrCH2CH2Br
Al Br3 + heat
Br
+
HBr
(a) What type of reaction is the reaction of bromine with
(i) ethene,
.............................................................................................................................................
(ii) benzene?
.............................................................................................................................................
[1]
(b) Write an equation to show the formation of the electrophile during the reaction between bromine
and benzene.
.............................................................................................................................................. [1]
(c) Each of these reactions involves an intermediate.
(i) Draw the structure of the intermediate in each reaction.
H 2C
CH2 + Br2 →
+
Br2
(ii) Suggest why the product of the reaction between bromine and benzene, bromobenzene,
is still unsaturated.
.............................................................................................................................................
[3]
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11
(d) When methylbenzene is nitrated, 4-nitromethylbenzene is formed, but when benzoic acid is
nitrated, 3-nitrobenzoic acid is produced.
Consider the following synthesis of 3-chlorobenzoic acid, F, from methylbenzene.
Use the information given above to suggest
●
●
the structure of the intermediate E,
the reagents and conditions needed for reactions 1 and 2.
CH3
CO2H
reaction 1
reaction 2
Cl
F
E
reagents and conditions for reaction 1
....................................................................................................................................................
reagents and conditions for reaction 2
....................................................................................................................................................
[3]
(e) Consider the following synthesis of 3-chlorophenylmethylamine, H, from F.
Suggest
●
●
the structure of the intermediate G,
the reagents for reactions 3 and 4.
CO2H
CONH2
reaction 3
NH3
reaction 4
Cl
Cl
F
CH2NH2
Cl
H
G
reagents for reaction 3
....................................................................................................................................................
reagents for reaction 4
....................................................................................................................................................
[3]
[Total: 11]
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5
Although now remembered for his music, the Russian composer Alexander Borodin was a chemist.
He is credited with the discovery of the aldol reaction, a product of which is compound J.
J shows the following properties:
●
●
●
●
●
its molecular formula is C4H8O2,
it is neutral,
it reacts with sodium metal,
it reacts with Fehling's solution,
it does not react with aqueous bromine.
(a) Suggest which functional groups are responsible for the reactions with
(i) sodium,
.............................................................................................................................................
(ii) Fehling's solution.
.............................................................................................................................................
[2]
(b) The result of the bromine test shows a functional group is absent from compound J.
Suggest the identity of this functional group.
.............................................................................................................................................. [1]
(c) In the boxes below, draw three possible straight-chain structures for J that fit the above
results, and that are structural isomers of each other.
K
L
M
[3]
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(d) Compound J reacts with alkaline aqueous iodine to give a pale yellow precipitate.
(i) Which functional group does this reaction show that J contains?
.............................................................................................................................................
(ii) Which of your three structures K, L or M contains this group and is therefore J?
.............................................................................................................................................
[2]
(e) Compound J exists as stereoisomers.
(i) Name the type of stereoisomerism shown by J.
.............................................................................................................................................
(ii) Draw two structures of J to illustrate this stereoisomerism.
[2]
[Total: 10]
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14
Section B
Answer all the questions in the spaces provided.
6
This question looks at the formation and breakdown of protein chains in the body.
(a) Proteins are formed from chains of amino acid monomers joined together.
The structures of two amino acids, valine and serine are shown.
CH3
O
O
OH
CH3
OH
HO
NH2
NH2
valine (val)
serine (ser)
(i) Draw the structure of the dipeptide val-ser, showing the peptide bond in displayed form.
(ii) What type of reaction has taken place in order to form this dipeptide?
.............................................................................................................................................
(iii) Identify the other molecule produced in this reaction.
.............................................................................................................................................
[4]
(b) Both DNA and RNA are involved in protein synthesis.
Complete the table to show three differences between the structures of DNA and RNA.
DNA
RNA
1
2
3
[3]
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15
(c) In protein synthesis, sections of the DNA are copied by mRNA and this, in turn, is read by the
ribosome in order to assemble the amino acids for the new protein chain. Each group of three
bases codes for one amino acid, with some amino acids having several codes. The codes are
summarised in the table.
UUU
UUC
UUA
UUG
phe
phe
leu
leu
UCU
UCC
UCA
UCG
ser
ser
ser
ser
UAU
UAC
UAA
UAG
tyr
tyr
stop
stop
UGU
UGC
UGA
UGG
cys
cys
stop
trp
CUU
CUC
CUA
CUG
leu
leu
leu
leu
CCU
CCC
CCA
CCG
pro
pro
pro
pro
CAU
CAC
CAA
CAG
his
his
gln
gln
CGU
CGC
CGA
CGG
arg
arg
arg
arg
AUU
AUC
AUA
AUG
ile
ile
ile
ACU
ACC
ACA
ACG
thr
thr
thr
thr
AAU
AAC
AAA
AAG
asn
asn
lys
lys
AGU
AGC
AGA
AGG
ser
ser
arg
arg
GCU
GCC
GCA
GCG
ala
ala
ala
ala
GAU
GAC
GAA
GAG
asp
asp
glu
glu
GGU
GGC
GGA
GGG
gly
gly
gly
gly
GUU
GUC
GUA
GUG
met/
start
val
val
val
val
In general the amino acid chains start with the code AUG, and end with one of the three ‘stop’
codes shown in the table.
(i) Use the abbreviations to show the sequence of amino acids in the peptide for the base
sequence shown.
– AUGCUAACACCGGAGUAA –
.............................................................................................................................................
(ii) Sometimes an error can occur in the base sequence.
What are these errors called?
.............................................................................................................................................
(iii) This type of error can lead to the formation of a protein with a different structure from
the original, as in sickle cell anaemia. In this case the amino acid glutamic acid (glu) is
replaced by valine (val) in the protein as a result of one base being changed in a three
base code.
Use the table to suggest the change of base that causes this.
.............................................................................................................................................
[3]
[Total: 10]
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7
Modern methods of chemical analysis often rely on the interpretation of data gathered from
instrumental techniques.
(a) Electrophoresis and paper chromatography can both be used to separate amino acids from a
mixture obtained from polypeptides.
d.c. power
supply
+
lid
glass slides
–
paper
solvent
front
mixtures placed
here
amino acid
mixture placed here
filter paper soaked
in buffer solution
electrophoresis
solvent
paper chromatography
In each case, give one property of the amino acids that causes their separation.
electrophoresis ..........................................................................................................................
....................................................................................................................................................
paper chromatography ..............................................................................................................
....................................................................................................................................................
[2]
(b) Amino acids are colourless.
How are the positions of the different amino acids made visible so that measurements can be
made?
....................................................................................................................................................
.............................................................................................................................................. [1]
(c) Which measurements need to be made in order to identify individual amino acids in paper
chromatography?
....................................................................................................................................................
.............................................................................................................................................. [1]
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(d) The diagram shows the results of electrophoresis on a mixture of the amino acids glycine,
lysine and glutamic acid at pH 7.0. The structures of the amino acids at pH 7.0 are shown.
glycine:
lysine:
glutamic acid:
H3N+CH2CO2–
H3N+CH(CH2CH2CH2CH2NH3+)CO2–
H3N+CH(CH2CH2CO2–)CO2–
–
+
spot of mixture
applied here
–
+
R
S
T
Identify the amino acids responsible for the spots labelled R, S and T.
R ................................................................................................................................................
S ................................................................................................................................................
T ................................................................................................................................................
[3]
(e) This diagram shows the results of two-way paper chromatography of a mixture of amino acids.
solvent 1
mixture
applied here
X
solvent 2
To answer these questions you need to indicate clearly on the diagram above as directed in
the questions.
(i) Put a U next to the amino acid that travelled furthest in solvent 2.
(ii) Put a ring around the two amino acids that were not separated in solvent 1.
(iii) Put a W next to the amino acid that was very soluble in both solvents.
[3]
[Total: 10]
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8
Polymers consist of monomers joined by either addition or condensation reactions.
(a) Name an example of a synthetic addition polymer and a synthetic condensation polymer.
addition polymer ........................................................................................................................
condensation polymer ...............................................................................................................
[2]
(b) Addition polymers are long-term pollutants in the environment but condensation polymers are
often biodegradable.
(i) What type of reaction occurs when condensation polymers biodegrade?
.............................................................................................................................................
(ii) Identify two functional groups that could undergo this type of reaction.
.............................................................................................................................................
[2]
(c) Petroleum is a non-renewable resource from which a wide range of useful polymers is currently
produced. Current polymer research is looking at renewable plant material as a potential
source of monomers.
Two monomers obtained from plants are shown.
CH3CH(OH)COOH
HOCH2COOH
Draw the displayed formula of the repeat unit of a polymer using both monomers.
[2]
(d) Monomers obtained from plant sources do not usually form addition polymers.
Suggest why this is.
....................................................................................................................................................
.............................................................................................................................................. [1]
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(e) The diagrams show sections of two polymers Y and Z.
O
H
N
O
N
N
O
H
Y
H
Z
(i) What would be the main force between the chains in each polymer?
Y .........................................................................................................................................
Z .........................................................................................................................................
(ii) Which is likely to be the more hydrophilic of these two polymers? Explain your answer.
.............................................................................................................................................
.............................................................................................................................................
[3]
[Total: 10]
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2
Section A
Answer all the questions in the spaces provided.
1
(a) The oxidation of nitrogen(II) oxide is shown in the equation.
2NO(g) + O2(g) → 2NO2(g)
The initial rate of this reaction was measured, starting with different concentrations of the two
reactants. The following results were obtained.
experiment
number
[NO]
/ mol dm–3
[O2]
/ mol dm–3
initial rate
/ mol dm–3 s–1
1
0.032
0.012
4.08 × 10–3
2
0.032
0.024
8.15 × 10–3
3
0.064
0.024
3.28 × 10–2
4
0.096
0.036
(i) Use the data in the table to determine the order with respect to each reactant. Show your
reasoning.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(ii) Calculate the initial rate in experiment 4. Give your answer to two significant figures.
initial rate = ............................. mol dm–3 s–1
(iii) Write the rate equation for this reaction.
.............................................................................................................................................
(iv) Use the results of experiment 1 to calculate the rate constant, k, for this reaction.
Include the units of k.
rate constant, k = .......................................... units ..........................................
[6]
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(b) (i) On the following axes
●
●
draw two Boltzmann distribution curves, at two different temperatures, T1 and T2 (T2 > T1),
label the curves and the axes.
(ii) State and explain, using your diagram, the effect of increasing temperature on the rate of
reaction.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
[5]
(c) The compound nitrosyl fluoride, NOF, can be formed by the following reaction.
2NO(g) + F2(g)
2NOF(g)
The rate is first order with respect to NO and F2.
The reaction mechanism has two steps.
Suggest equations for the two steps of this mechanism, stating which is the rate determining
slower step.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
[Total: 13]
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2
(a) Complete the electron configurations for Ni and Ni2+.
3d
Ni
[Ar]
Ni2+
[Ar]
4s
[2]
(b) The presence of electrons in d orbitals is responsible for the colours of transition element
compounds.
(i) The d orbitals in an isolated transition metal atom or ion are all at the same energy level.
What term is used to describe orbitals that are at the same energy level?
.............................................................................................................................................
(ii) Complete the diagram to show the splitting of the d orbital energy levels in an octahedral
complex ion.
energy
(iii) On the axes below, sketch the shapes of one d orbital from the lower energy level and one
d orbital from the higher energy level.
lower energy level
higher energy level
z
z
x
x
y
y
[4]
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(c) The octahedral complex [Ni(H2O)6]2+ is green. Explain the origin of the colour of this complex.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
(d) When NH3(aq) is added to the green solution containing [Ni(H2O)6]2+, a grey-green precipitate,
A, is formed. This precipitate dissolves in an excess of NH3(aq) to give a blue-violet solution, B.
Suggest formulae for A and B and write equations for the two reactions producing A and B.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [4]
[Total: 13]
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3
(a) Natural phosphorus consists of one isotope, 31P. Chlorine exists naturally as two isotopes, 35Cl
and 37Cl, in the relative abundance ratio of 3 : 1.
(i) The mass spectrum of PCl 3 contains several peaks corresponding to a number of
molecular fragments.
Suggest the isotopic composition of the fragments with the following mass numbers.
mass number
isotopic composition
101
103
105
(ii) Predict the relative ratios of the peak heights of the three peaks corresponding to these
fragments.
.............................................................................................................................................
[4]
(b) Phosphorus reacts with chlorine to form a variety of chlorides.
PCl 5 is an example of a compound that exists as two structures depending on the conditions.
2PCl 5(g)
[PCl 4]+[PCl 6]–(s)
(i) Draw a ‘dot-and-cross’ diagram to show the bonding in PCl 5. Show the outer electrons
only.
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7
(ii) Draw diagrams to suggest the shapes of [PCl 4]+ and [PCl 6]–.
[PCl 4]+
[PCl 6]–
[3]
(c) (i) Phosphorus(III) oxide, P4O6, contains no P–P or O–O bonds.
In the P4O6 molecule, all oxygen atoms are divalent and all phosphorus atoms are trivalent.
Sketch a structure for P4O6.
(ii) P4O6 can act as a ligand.
What is meant by the term ligand ?
.............................................................................................................................................
.............................................................................................................................................
[2]
(d) Phosphate ions in water can be removed by adding a solution containing Ca2+(aq) ions, which
form a precipitate of calcium phosphate, Ca3(PO4)2.
(i) Write an expression for the Ksp of Ca3(PO4)2.
Ksp =
(ii) The solubility of Ca3(PO4)2 is 2.50 × 10–6 mol dm–3 at 298 K.
Calculate the solubility product, Ksp, of Ca3(PO4)2 at this temperature. Include the units.
Ksp = ..................................................................
© UCLES 2014
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[4]
[Turn over
8
(e) (i) What is meant by the term lattice energy?
.............................................................................................................................................
.............................................................................................................................................
(ii) Explain why the lattice energy of calcium phosphate is less exothermic than that of
magnesium phosphate.
.............................................................................................................................................
.............................................................................................................................................
[3]
[Total: 16]
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4
(a) Methylbenzene undergoes electrophilic substitution with nitronium ions, NO2+.
Nitronium ions are generated by the reaction between concentrated sulfuric acid and
concentrated nitric acid.
(i) Construct an equation for the formation of nitronium ions, NO2+, by this method.
.............................................................................................................................................
(ii) Complete the scheme to show the mechanism for this reaction. Use curly arrows to show
the movement of electron pairs.
CH3
NO2+
[4]
(b) (i) Describe and explain the relative acidities of chloroethanoic acid and ethanoic acid.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(ii) Describe and explain the relative acidities of phenol and ethanol.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
[3]
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(c) Phenyl 2-hydroxybenzoate is an antiseptic.
O
O
OH
phenyl 2-hydroxybenzoate
Complete the following table about the reactions of phenyl 2-hydroxybenzoate with the three
reagents.
reagent
structure of product(s)
type of reaction
Na
excess
Br2(aq)
excess hot
NaOH(aq)
[6]
[Total: 13]
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5
(a) Organohalogen compounds can undergo hydrolysis.
R–Cl + H2O → R–OH + HCl
State the relative rates of hydrolysis of the following compounds.
CH3CH2CH2Cl
CH3CH2COCl
C6H5Cl
Explain your answer.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
(b) Aminolaevulinic acid is involved in the synthesis of haemoglobin and chlorophyll.
O
H 2N
OH
O
aminolaevulinic acid
Name the three functional groups in aminolaevulinic acid.
............................................................................................................................................. [2]
(c) Aminolaevulinic acid reacts readily with bromoethane.
(i) Show the mechanism of the first step of this reaction on the diagram. Include all necessary
curly arrows, lone pairs and relevant dipoles.
O
O
H 2N
OH
intermediate
H 3C
O
H 3C
CH2
© UCLES 2014
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OH
O
13
(ii) Name the mechanism in (c)(i).
.............................................................................................................................................
(iii) Identify the non-organic product formed in this reaction.
.............................................................................................................................................
[5]
(d) Three reactions of aminolaevulinic acid are shown. Draw the structures of the products W, X
and Y in the boxes below.
O
NaBH4
H2N
OH
O
aminolaevulinic acid
CH3COCl
Y
HCl (aq), warm
X
W
[3]
(e) Aminolaevulinic acid can undergo polymerisation.
Draw the structure of the polymer showing two repeat units. The linkages between the
monomer units should be shown fully displayed.
[2]
[Total: 15]
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Section B
Answer all the questions in the spaces provided.
6
(a) A mixture of amino acids can be separated by electrophoresis. During an electrophoresis
experiment,
●
●
●
different amino acids move in different directions,
different amino acids move at different speeds,
some amino acids do not move at all.
Explain these observations.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
(b) (i) A mixture of amino acids can also be separated by thin-layer chromatography.
Identify the mobile and the stationary phases in this type of chromatography.
mobile phase ......................................................................................................................
stationary phase .................................................................................................................
(ii) What is the process by which thin-layer chromatography can separate a mixture?
.............................................................................................................................................
[3]
(c) State three structural features of DNA.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
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(d) Some diseases are caused by a mutation in the DNA base sequence which results in one
amino acid being replaced by another during protein synthesis.
Suggest what changes in the interactions that form the tertiary structure would result from a
mutation that replaced a valine residue with a serine residue.
O
NH
CH
HC
C
O
replaced by
CH3
NH
CH
C
CH2
OH
CH3
val
ser
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
[Total: 11]
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7
(a) Oseltamivir is an antiviral drug that slows the spread of the influenza (flu) virus.
O
O
O
HN
O
NH2
oseltamivir
Circle two bonds, each in a different functional group, that could be easily hydrolysed in the
body.
[2]
(b) Oseltamivir is a chiral drug. This drug is usually taken as a single optical isomer rather than as
a mixture of isomers.
Suggest one benefit of taking a drug in this way.
....................................................................................................................................................
.............................................................................................................................................. [1]
(c) Oseltamivir is a competitive inhibitor of an enzyme produced by the flu virus.
Explain the meaning of the term competitive inhibitor and state how its action could be
overcome.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
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(d) ATP plays an important role in metabolic reactions in living organisms.
NH2
N
N
N
O
O
N
H
H
HO
H
CH2O
P
H
O–
O
O
P
O–
O
O
P
O–
O–
OH
ATP
What is the function of ATP in living organisms?
....................................................................................................................................................
.............................................................................................................................................. [1]
[Total: 7]
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8
T is a saturated alcohol. It was analysed by mass spectroscopy and NMR spectroscopy.
In the mass spectrum, the molecular ion peak, M, was at an m/e value of 74 and the ratio of the
heights of the M and M+1 peaks was 20.4 : 0.9.
(a) (i) Use the ratio of the heights of the M and M+1 peaks to calculate the number of carbon
atoms in a molecule of T.
(ii) What is the molecular formula of T?
molecular formula = .....................................
[3]
(b) The NMR spectrum of T given below shows four absorptions. The absorption at 1.8 ppm is a
multiplet and that at 2.5 ppm is a singlet.
11
10
9
8
7
6
5
δ / ppm
4
3
2
1
0
(i) Use this information and your answer to (a)(ii) to deduce the structure of T.
T
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19
(ii) Describe and explain which type of proton is responsible for each of the absorptions.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(iii) The absorption at 1.8 ppm is a multiplet and that at 2.5 is a singlet.
State and explain the splitting patterns of the other absorptions, at 0.9 and 3.4 ppm.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(iv) Describe and explain how the NMR spectrum of T dissolved in D2O would differ from the
one shown.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
[9]
[Total: 12]
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2
Section A
Answer all the questions in the spaces provided.
1
(a) Chlorine exists naturally as a mixture of two isotopes, 35Cl and 37Cl , in the abundance ratio of 3 : 1.
The mass spectrum of chlorine consists of five peaks.
(i) Suggest the mass numbers for these five peaks and the identities of the species
responsible.
mass number
formula of species
(ii) Predict the ratios of the abundances of the three species with the highest mass numbers.
ratio of abundances = ........................................
[4]
(b) Strontium chloride, SrCl 2, can be used to produce a red colour in fireworks.
(i) Draw the ‘dot-and-cross’ diagram for strontium chloride. Show outer shell electrons only.
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3
(ii) Use the following data, together with relevant data from the Data Booklet, to calculate
a value for the lattice energy of strontium chloride. You may find it helpful to construct a
Born-Haber cycle.
electron affinity per mole of chlorine atoms
–349 kJ mol–1
standard enthalpy of atomisation of Sr(s)
+164 kJ mol–1
standard enthalpy of formation of SrCl 2(s)
–830 kJ mol–1
lattice energy = .................. kJ mol–1
[5]
(c) Strontium nitrate, Sr(NO3)2, can also be used to produce a red colour in fireworks.
(i) Strontium nitrate can easily be prepared from strontium carbonate, SrCO3.
Suggest an equation for this preparation of strontium nitrate.
.............................................................................................................................................
(ii) Write an equation for the reaction that occurs when strontium nitrate is heated.
.............................................................................................................................................
[2]
(d) Describe and explain the trend in the thermal stabilities of the nitrates of the Group II elements.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
[Total: 14]
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2
(a) Bromate(V) ions, BrO3–, react with bromide ions in the presence of acid to produce bromine.
Write an ionic equation for this reaction.
....................................................................................................................................................
.............................................................................................................................................. [2]
(b) The initial rate of this reaction was measured, starting with different concentrations of the three
reactants.
The following results were obtained.
experiment
number
[BrO3–]
/ mol dm–3
[Br –]
/ mol dm–3
[H+]
/ mol dm–3
initial rate
/ mol dm–3 s–1
1
0.040
0.020
0.50
2.64 × 10–4
2
0.040
0.020
1.00
1.06 × 10–3
3
0.040
0.080
0.50
1.06 × 10–3
4
0.080
0.020
0.50
5.21 × 10–4
(i) Use the data in the table to determine the order with respect to each reactant. Show your
reasoning.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(ii) Write the rate equation for this reaction.
.............................................................................................................................................
(iii) Use the results of experiment 1 to calculate the rate constant, k, for this reaction.
Include the units of k.
rate constant, k = .......................................... units ..........................................
[6]
[Total: 8]
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3
Transition elements have characteristic properties due to their partially-filled d orbitals.
(a) (i) Which two elements in the first row of the d-block have only one electron in the 4s orbital of
their neutral atoms?
.............................................................................................................................................
(ii) The d orbitals in an isolated transition metal atom or ion are described as being degenerate.
What is meant by the term degenerate?
.............................................................................................................................................
(iii) Sketches of the shapes of the atomic orbitals from the d subshell are shown.
In an octahedral complex, the d orbitals are split into two groups at different energy levels.
On the diagram below, write an ‘H’ in the box under each of the orbitals at the higher
energy level.
z
z
x
y
y
z
x
z
x
y
y
z
x
x
y
[4]
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6
(b) The following scheme shows some reactions of Cu2+(aq).
a few drops of NH3(aq)
2+
Cu (aq)
pale blue precipitate A
concentrated
HCl
excess NH3(aq)
solution of C
solution of B
heat with Cu(s)
[CuCl 2]–(aq)
(i) Suggest the formula of each of the following.
A .........................................................................................................................................
B .........................................................................................................................................
C .........................................................................................................................................
(ii) State the colour of the following solutions.
solution of B ........................................................................................................................
solution of C ........................................................................................................................
(iii) Name the type of reaction that occurs when C is heated with copper.
.............................................................................................................................................
Deduce the role of the copper metal in this reaction.
.............................................................................................................................................
[6]
(c) When the solution containing the complex [CuCl 2]– is poured into water, a precipitate of CuCl
is formed. CuCl is white because it does not absorb visible light.
Explain why CuCl does not absorb visible light.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
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(d) The complex ion [Cr(H2O)6]3+ is coloured because it absorbs visible light. The absorption
spectrum for [Cr(H2O)6]3+ is shown below.
absorbance
400
500
violet
600
red
wavelength / nm
Suggest the colour of this complex ion. Explain your answer.
....................................................................................................................................................
.............................................................................................................................................. [2]
[Total: 14]
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8
4
(a) The following circuits were set up using aqueous hydrochloric and aqueous ethanoic acids as
electrolytes. Assume that the two circuits were identical apart from the electrolyte.
bulb
1
graphite
electrodes
bulb
2
switch
1 mol dm–3
HCl (aq)
graphite
electrodes
switch
1 mol dm–3
CH3CO2H(aq)
When the switches were closed, bulb 1 was brighter than bulb 2. Explain why.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
(b) (i) State what is meant by a buffer solution.
.............................................................................................................................................
.............................................................................................................................................
(ii) Outline how a buffer solution can be prepared from ethanoic acid and a named base.
.............................................................................................................................................
.............................................................................................................................................
[4]
(c) Amino acids such as alanine, CH3CH(NH2)CO2H, can act as a buffer solution.
Construct two equations to illustrate this.
equation 1
equation 2
[2]
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9
(d) Tartaric acid is present in many plants.
OH
O
HO
OH
O
OH
tartaric acid
(i) Tartaric acid has two dissociation constants, K1 and K2, for which the pKa values are 2.99
and 4.40.
Suggest equations showing the two dissociations that give rise to these pKa values.
pKa 2.99
pKa 4.40
(ii) One stereoisomer of tartaric acid is shown.
HO
H
CO2H
HO2C
H
OH
Complete the diagrams showing two other stereoisomers of tartaric acid.
CO2H
CO2H
[4]
[Total: 12]
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10
5
L-DOPA is used in the treatment of Parkinson's disease. It can be prepared from vanillin.
HO
HO
NH2
CO2H
HO
H
CH3O
O
L-DOPA
vanillin
(a) L-DOPA and vanillin each contain an aromatic benzene ring.
Describe, with the aid of a diagram, the bonding and shape of a molecule of benzene, C6H6.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [5]
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(b) A student carried out some reactions with samples of L-DOPA and vanillin using reagents X, Y
and Z.
●
●
●
Reagent X reacted with L-DOPA and with vanillin.
Reagent Y reacted with L-DOPA but not with vanillin.
Reagent Z reacted with vanillin but not with L-DOPA.
Assume that the CH3O– group in vanillin does not react.
Suggest possible identities of reagents X, Y and Z and give the structures of the organic
products that were formed.
Reagent X ..................................................................................................................................
product with L-DOPA
product with vanillin
Reagent Y ..................................................................................................................................
product with L-DOPA
Reagent Z ..................................................................................................................................
product with vanillin
[7]
[Total: 12]
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6
Methoxetamine is a derivative of the pharmaceutical drug, ketamine.
O
OCH3
NHCH2CH3
methoxetamine
(a) (i) What is the molecular formula of methoxetamine?
.............................................................................................................................................
(ii) On the diagram above, circle any chiral centres that are present in methoxetamine.
(iii) Name two functional groups in methoxetamine, in addition to the aryl group.
.............................................................................................................................................
[4]
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(b) In the table, complete the structure of each of the compounds formed when methoxetamine is
reacted with the following reagents.
State the type of reaction in each case.
reagent
structure of product
type of reaction
(i) LiAl H4
OCH3
(ii) HCl (aq)
OCH3
(iii) CH3COCl
OCH3
[6]
[Total: 10]
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14
Section B
Answer all the questions in the spaces provided.
7
(a) Explain what is meant by the term partition coefficient.
....................................................................................................................................................
.............................................................................................................................................. [2]
(b) When 20 cm3 of ethoxyethane were shaken with 75 cm3 of an aqueous solution containing
5.00 g of an organic compound, J, in 75 cm3 of water, it was found that 2.14 g of J were extracted
into the ethoxyethane.
Calculate the partition coefficient, Kpartition, of J between ethoxyethane and water.
Kpartition = ...................... [2]
(c) In a new experiment
●
●
●
10 cm3 of ethoxyethane were shaken with 75 cm3 of an aqueous solution containing 5.00 g
of J and the layers were separated.
The aqueous layer was shaken with a second 10 cm3 portion of ethoxyethane and the
layers were separated.
The two organic layers were combined.
Use the value of Kpartition you calculated in (b) to calculate the total mass of J extracted by this
procedure.
total mass of J = ...................... [2]
(d) Paper chromatography and gas / liquid chromatography both rely on the partition of compounds
between mobile and stationary phases.
(i) Identify the mobile phase in paper chromatography.
.............................................................................................................................................
(ii) Suggest what type of liquid is used for the stationary phase in gas / liquid chromatography.
.............................................................................................................................................
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(iii) Both these techniques can be used to separate mixtures.
State what you would measure in order to distinguish between the components in the mixture
in
1. paper chromatography, ..................................................................................................
2. gas / liquid chromatography. ...........................................................................................
[4]
(e) A mixture of three compounds was analysed by paper chromatography using a non-polar
solvent. The resulting chromatogram is shown.
solvent front
1
2
3
mixture
Identify which compound is responsible for each spot.
compound
spot
CO2H
CH2OH
CO2H
CO2H
[1]
[Total: 11]
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8
(a) Analysis of a sample of DNA showed that 33% of the nitrogenous bases present was guanine.
Calculate the percentages of the other bases in this sample of DNA.
adenine ...........................%
cytosine ...........................%
thymine ...........................%
[2]
(b) Many drug molecules are chiral, but are often produced as a mixture of optical isomers.
(i) Suggest why a larger mass of the mixture is required than of a single optical isomer.
.............................................................................................................................................
.............................................................................................................................................
(ii) Suggest a problem that might arise as a result of taking a mixture of optical isomers.
.............................................................................................................................................
.............................................................................................................................................
[2]
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17
(c) There are four structural isomers with the molecular formula C5H10O that are aldehydes.
(i) Draw the structures of these aldehydes.
P
Q
R
S
(ii) The NMR spectrum of one of these isomers contains four absorptions.
Which isomer P, Q, R or S gives this spectrum?
isomer ...............................................
(iii) Predict the number of absorptions that would be given by each of the other three isomers.
isomer letter (P, Q, R or S)
number of absorptions
[6]
[Total: 10]
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18
9
(a) Polymers can be formed by addition or condensation polymerisation.
Complete the table.
polymer
method of polymerisation
nylon
PVC (polychloroethene)
Terylene
[1]
(b) Nomex is a polymeric material with excellent flame-resistant properties.
It contains a polymer made from the two monomers shown below.
H 2N
NH2
HO2C
CO2H
Draw the structure of the polymer showing two repeat units. The linkages between monomer
units should be shown fully displayed.
[2]
(c) Proteins are natural polymers. Explain what is meant by the primary structure of a protein.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [1]
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(d) Use the diagram to show an example of how the α-helix secondary structure in proteins is
stabilised.
....................................................................................................................................................
.............................................................................................................................................. [2]
(e) The tertiary structure of a protein is destroyed during the process of denaturation.
Explain how this can occur by
(i) the addition of alkali,
.............................................................................................................................................
.............................................................................................................................................
(ii) the addition of Hg2+ ions,
.............................................................................................................................................
.............................................................................................................................................
(iii) heating to 70 °C.
.............................................................................................................................................
.............................................................................................................................................
[3]
[Total: 9]
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2
Section A
Answer all the questions in the spaces provided.
1
(a) Complete the electronic configurations of the following atoms.
oxygen: 1s2..........................................
fluorine: 1s2..........................................
[1]
(b) A compound of fluorine and oxygen contains three atoms in each molecule.
(i)
Predict its formula.
....................................................................................................................................... [1]
(ii)
Draw a ‘dot-and-cross’ diagram to show its bonding.
[1]
(iii)
Suggest the shape of this molecule.
....................................................................................................................................... [1]
(c) (i) Use E o values from the Data Booklet to predict the relative oxidising abilities of fluorine
and chlorine.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(ii)
Predict the type of reaction that would occur between the interhalogen compound chlorine
fluoride, Cl F, and potassium bromide solution.
....................................................................................................................................... [1]
(iii)
Construct an equation for this reaction.
....................................................................................................................................... [1]
[Total: 8]
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2
(a) Both chloroalkanes and acyl chlorides react with water, but only acyl chlorides fume in moist
air.
(i)
State which product causes the fumes in this reaction.
....................................................................................................................................... [1]
(ii)
Explain why the reactivities of chloroalkanes and acyl chlorides differ.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [1]
(b) Compound R is a useful intermediate in the synthesis of pharmaceutical compounds. It can be
made from compound P by the following route.
CO2H
step 1
COCl
step 2
COCl
CO2H
step 3
CH3CH2NH2
P, C8H10
NCH2CH3
step 4
R
Q, C10H9NO2
(i)
Suggest structures for the starting material P and the intermediate Q.
(ii)
Suggest reagents and conditions for the following steps in the above scheme.
[2]
step 1 ..................................................................................................................................
step 2 ..................................................................................................................................
step 4 ..................................................................................................................................
[3]
[Total: 7]
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4
3
(a) The mass spectrum of the element magnesium is shown below.
relative
abundance
(%)
50
0
23
24
25
26
27
m/e
(i)
From the mass spectrum, complete the table with the relative abundances of the three
isotopes.
isotope
24
Mg
25
Mg
26
Mg
relative abundance
[1]
(ii)
Use your values in (i) to calculate the relative atomic mass, Ar, of magnesium to two
decimal places.
Ar (Mg) = ........................... [1]
© UCLES 2015
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5
(b) (i) Describe and explain the trend in the thermal stabilities of the nitrates of the Group II
elements down the group.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [3]
When lithium nitrate, LiNO3, is heated, it readily decomposes giving off a brown gas. This
reaction is similar to that which occurs when magnesium nitrate is heated, but it does not occur
with other Group I nitrates.
(ii)
Suggest an equation for the action of heat on LiNO3.
....................................................................................................................................... [1]
(iii)
Suggest why the Group I nitrates other than LiNO3 do not decompose in this way when
heated.
.............................................................................................................................................
....................................................................................................................................... [1]
[Total: 7]
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4
(a) Silver sulfate, Ag2SO4, is sparingly soluble in water. The concentration of its saturated solution
is 2.5 × 10–2 mol dm–3 at 298 K.
(i)
Write an expression for the solubility product, Ksp, of Ag2SO4, and state its units.
Ksp =
(ii)
units: .............................. [1]
Calculate the value for Ksp(Ag2SO4) at 298 K.
Ksp = ............................................... [1]
(b) Using Ag2SO4 as an example, complete the following Hess' Law energy cycle relating the
,
●
lattice energy,
●
enthalpy change of solution,
●
enthalpy change of hydration,
, and
.
On your diagram:
●
include the relevant species in the two empty boxes,
●
label each enthalpy change with its appropriate symbol,
●
complete the remaining two arrows showing the correct direction of enthalpy change.
..............................
Ag2SO4(s)
..............................
..............................
[4]
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7
(c) An electrochemical cell is set up as follows.
V
Pt
Ag
Ag2SO4(aq)
Fe2(SO4)3(aq)
+
FeSO4(aq)
(i)
Ag2SO4(s)
Use the Data Booklet to calculate the value of
which electrode is the positive one.
= ..............................
(ii)
under standard conditions, stating
positive electrode: .............................. [1]
How would the actual Ecell of the above cell compare to the
Explain your answer.
under standard conditions?
.............................................................................................................................................
....................................................................................................................................... [1]
(iii)
How would the Ecell of the above cell change, if at all, if a few cm3 of concentrated Na2SO4(aq)
were added to
•
the beaker containing Fe3+(aq) + Fe2+(aq),
.............................................................................................................................................
•
the beaker containing Ag2SO4(aq)?
.............................................................................................................................................
[2]
(iv)
Explain any changes in Ecell you have stated in (iii).
.............................................................................................................................................
....................................................................................................................................... [1]
(d) Solutions of iron(III) sulfate are acidic due to the following equilibrium.
[Fe(H2O)6]3+(aq)
[Fe(H2O)5(OH)]2+(aq) + H+(aq)
Ka = 8.9 × 10–4 mol dm–3
Calculate the pH of a 0.1 mol dm–3 solution of iron(III) sulfate, Fe2(SO4)3.
pH = .........................
[2]
[Total: 13]
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5
(a) Atoms and ions of elements are made up from the three subatomic particles, protons, electrons
and neutrons, in varying amounts.
Complete the following table to show the number of each particle in 14C2–.
protons
14
electrons
neutrons
C2–
[2]
(b) Describe the observations you would make during the reactions, if any, of the following chlorides
with water.
Write equations for any reactions that occur.
CCl 4
observation ..................................................................................................................
......................................................................................................................................
equation .......................................................................................................................
GeCl 4 observation ..................................................................................................................
......................................................................................................................................
equation .......................................................................................................................
SnCl 4
observation ..................................................................................................................
......................................................................................................................................
equation .......................................................................................................................
[4]
(c) Suggest a reason for any difference in the reactivities of the chlorides given in (b).
....................................................................................................................................................
.............................................................................................................................................. [1]
(d) Use data from the Data Booklet to explain why an aqueous solution of SnCl 2 reacts with Cl 2(g)
but an aqueous solution of PbCl 2 does not.
Write an equation for the reaction.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
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(e) (i) State the relationship between the Faraday constant and the Avogadro constant.
....................................................................................................................................... [1]
(ii)
When a current of 1.2 A was passed through dilute sulfuric acid for 30 minutes, it was
found that 130 cm3 of oxygen, measured at 25 °C and 1 atm, was collected at the anode.
The following reaction takes place.
2H2O(l) → 4H+(aq) + O2(g) + 4e–
Use these data and data from the Data Booklet to calculate a value for the Avogadro
constant, L, by calculating
•
•
•
•
•
the number of moles of oxygen produced,
the number of moles of electrons needed for this,
the number of coulombs passed,
the number of electrons passed,
the number of electrons in one mole of electrons (L).
L = ............................................... mol–1
[4]
[Total: 15]
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6
1,3-dimethylbenzene is a useful starting material for several commercially important compounds.
(a) The artificial ‘musk ketone’, A, is a perfume agent added to many cosmetics and detergents. It
is made from 1,3-dimethylbenzene by the following route.
O
step 1
step 2
O
step 3
O2N
NO2
1,3-dimethylbenzene
‘musk ketone’ A
(i)
The only by-product of step 2 is HCl.
Suggest the reagent that was used in this step.
....................................................................................................................................... [1]
(ii)
Suggest the type of reaction that is occurring during both step 2 and step 3.
....................................................................................................................................... [1]
(iii)
State the reagents and conditions needed for step 3.
....................................................................................................................................... [1]
(iv)
Suggest the structures of the two products formed when A is reacted with alkaline aqueous
iodine.
[2]
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11
(b) 1,3-dimethylbenzene is also a starting material for the synthesis of the polymer Nomex, used
in fireproof protective clothing worn by firefighters, military pilots and racing car drivers. The
polymer is made from 1,3-dimethylbenzene and 1,3-dinitrobenzene by the following route.
step 1
HO2C
CO2H
step 2
H 2N
NH2
1,3-dimethylbenzene
O2N
NO2
1,3-dinitrobenzene
step 3
Nomex
(i)
Draw the structure of one repeat unit of Nomex in the box above.
(ii)
What type of polymer is Nomex?
[1]
....................................................................................................................................... [1]
(iii)
Suggest the by-product formed during step 3.
....................................................................................................................................... [1]
(iv)
Suggest reagents and conditions for step 2.
....................................................................................................................................... [1]
(v)
Suggest how and why the properties of the polymer might change if some of the diamine
monomer were replaced with 1,3,5-triaminobenzene.
H 2N
NH2
NH2
1,3,5-triaminobenzene
.............................................................................................................................................
....................................................................................................................................... [1]
[Total: 10]
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7
(a) Long chain alkanes such as 4-methylheptane can be ‘cracked’ to produce shorter chain
hydrocarbons.
B
C 3H 8
+
a mixture of C, D and E
(isomers of C5H10)
4-methylheptane
(i)
State the conditions necessary for this reaction to take place.
....................................................................................................................................... [1]
(ii)
Suggest the structure of B.
B
[1]
(iii)
Compounds C, D and E are isomers with the molecular formula C5H10.
On heating with concentrated acidified KMnO4,
●
compound C gives CO2 and compound F (C4H8O2),
●
D and E each give a 1 : 1 mixture of compounds G (C2H4O2) and H (C3H6O2).
Suggest structures for compounds C - H.
C
D
E
F
G
H
[3]
(iv)
Name the type of isomerism shown between D and E.
....................................................................................................................................... [1]
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13
(b) Propene, CH3CH=CH2, reacts with bromine to give 1,2-dibromopropane.
(i)
How is this reaction usually carried out?
....................................................................................................................................... [1]
(ii)
State the type of reaction that is occurring here.
....................................................................................................................................... [1]
(iii)
Draw the mechanism of this reaction, including the structures of any intermediates, and
any dipoles, lone pairs and curly arrows to show the movements of electrons.
[2]
[Total: 10]
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14
Section B
Answer all the questions in the spaces provided.
8
Proteins are formed by the polymerisation of amino acids.
(a) (i) State the type of chemical reaction used to form these polymer chains.
....................................................................................................................................... [1]
(ii)
The amino acids serine and valine can combine together to form a dipeptide.
OH
O
H 2N
OH
H 2N
OH
O
valine, val
serine, ser
Draw the skeletal structure of the dipeptide ‘val-ser’.
[2]
(iii)
Suggest how the type of amino acids in a protein determines its three-dimensional
structure.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
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(b) Using labelled diagrams or words as appropriate, explain
(i)
why a particular enzyme may only catalyse a specific reaction on a specific substrate,
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(ii)
how non-competitive inhibition of an enzyme-catalysed reaction can occur.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [3]
[Total: 10]
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16
9
(a) DNA fingerprinting has become a very important technique for analysing samples from living
or once-living organisms.
(i)
After extraction and purification, what is the first step in analysing a sample of DNA?
.............................................................................................................................................
....................................................................................................................................... [1]
(ii)
What can be done to increase the amount of DNA for analysis?
.............................................................................................................................................
....................................................................................................................................... [1]
(iii)
During electrophoresis, it is observed that amino acids can move in different directions or
not at all, whilst DNA fragments always move in the same direction.
Explain these two observations.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(iv)
DNA fingerprinting can also be useful in archaeology.
Which of the following would not be suitable for analysis by DNA fingerprinting?
Put a cross (x) in the appropriate box(es).
a piece of leather from an Egyptian tomb
a sample of skin from a mummified body
a fragment of ancient pottery
a piece of wood from a Roman chariot
[1]
(b) (i) X-ray crystallography can be used to help analyse the structure of macromolecules.
What does this technique tell us about a particular macromolecule?
.............................................................................................................................................
....................................................................................................................................... [1]
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17
(ii)
Which element will show up most strongly in the X-ray crystallography of a biological
polymer of general formula CvHwPxNyOz?
Explain your answer.
.............................................................................................................................................
....................................................................................................................................... [1]
(c) (i) Explain what is meant by a partition coefficient.
.............................................................................................................................................
....................................................................................................................................... [1]
(ii)
The partition coefficient of a particular pesticide between hexane and water is 6.0.
A solution contains 0.0042 g of the pesticide dissolved in 25 cm3 of water. The solution is
shaken with 25 cm3 of hexane.
Calculate the mass of pesticide that will be dissolved in the hexane layer at equilibrium.
[2]
[Total: 10]
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18
10 In recent years there has been worldwide interest in the possible extraction of ‘shale gas’ (a form
of natural gas) as an important energy source.
(a) One of the problems associated with using shale gas is its variable composition.
Table 1 shows the percentage composition of shale gas from four different sources J, K, L and M.
source
CH4
C 2 Hx
C 3H y
CO2
N2
J
80.3
8.1
2.3
1.4
7.9
K
82.1
14.0
3.5
0.1
0.3
L
88.0
0.8
0.7
10.4
0.1
M
77.5
4.0
0.9
3.3
14.3
In the formulae above, x and y are variables.
Table 1
(i)
Draw the structures of three possible compounds with the formula C3Hy.
[2]
(ii)
Which source of shale gas, J, K, L or M, will provide the most energy when burned?
Explain your answer.
.............................................................................................................................................
....................................................................................................................................... [1]
(iii)
Suggest two methods by which carbon dioxide can be removed from shale gas.
1 ..........................................................................................................................................
.............................................................................................................................................
2 ..........................................................................................................................................
.............................................................................................................................................
[2]
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(b) Table 2 shows a comparison of the relative amounts of pollutants produced when shale gas,
fuel oil and coal are burned to produce the same amount of energy.
air pollutant
CO2
shale gas
117
fuel oil
164
coal
208
CO
0.040
0.033
0.208
NO2
0.092
0.548
0.457
SO2
0.001
1.12
2.59
particulates
0.007
0.84
2.74
Table 2
(i)
Suggest why shale gas produces the smallest amount of CO2.
.............................................................................................................................................
....................................................................................................................................... [1]
(ii)
Explain which of the three fuels, shale gas, fuel oil or coal, is the largest contributor to
‘acid rain’.
fuel .................
.............................................................................................................................................
....................................................................................................................................... [1]
(iii)
Suggest a reason why fuel oil and coal produce more NO2 than shale gas.
.............................................................................................................................................
....................................................................................................................................... [1]
(iv)
State one environmental consequence of raised levels of
●
CO, ..............................................................................................................................
●
CO2. .............................................................................................................................
[2]
[Total: 10]
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2
Section A
Answer all the questions in the spaces provided.
1
(a) Complete the electronic configurations of the following atoms.
fluorine: 1s2..........................................
sulfur:
1s2..........................................
[1]
(b) (i) Write an equation to show the thermal decomposition of HCl.
....................................................................................................................................... [1]
(ii)
Using all relevant bond energy values from the Data Booklet, explain why the thermal
stability of HF is much more than that of HCl.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [1]
(c) Explain what is meant by the term electronegativity, and how it relates to the concept of bond
polarity.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
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(d) Sulfur and fluorine react together to give the covalent compound SF4.
(i)
Draw a ‘dot-and-cross’ diagram to show the bonding in SF4. Include all outer shell electrons
in your diagram.
[2]
(ii)
State whether a molecule of SF4 has a dipole moment. Explain your answer.
.............................................................................................................................................
....................................................................................................................................... [1]
(e) Suggest a reason why sulfur can form both SF4 and SF6 whereas oxygen can only form OF2.
....................................................................................................................................................
.............................................................................................................................................. [1]
(f)
(i) State a major source of atmospheric sulfur dioxide.
....................................................................................................................................... [1]
(ii)
State one environmental consequence of atmospheric sulfur dioxide.
....................................................................................................................................... [1]
[Total: 11]
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4
2
(a) A sample of lead consists of the following isotopes in the percentage abundances stated.
isotope
% abundance
204
Pb
1.9
206
Pb
24.8
207
Pb
21.4
208
Pb
51.9
Use these data to calculate the relative atomic mass of the sample of lead to two decimal
places.
Ar (Pb) = ........................... [2]
(b) Tin and lead both form oxides in oxidation states (II) and (IV).
(i)
How does the acid-base nature of tin(II) oxide compare to that of tin(IV) oxide?
....................................................................................................................................... [1]
(ii)
Illustrate your answer to (i) with equations, showing the reaction of each oxide with a
suitable acid or base, as appropriate.
SnO ....................................................................................................................................
SnO2 ...................................................................................................................................
[2]
(iii)
Describe the reactions, if any, that occur when separate samples of tin(IV) oxide and
lead(IV) oxide are heated in air.
Include any relevant observations and write equations for any reactions that occur.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [3]
[Total: 8]
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3
(a) Complete the table with the symbol of the ion that contains the number of protons, electrons
and neutrons stated in the following table. The first line has been completed as an example.
protons
electrons
neutrons
3
2
4
15
16
18
symbol
Li+
7
[2]
(b) Describe and explain the trend in the solubilities of the sulfates of the Group II elements down
the group.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [4]
(c) Calcium sulfate is sparingly soluble in water.
Describe and explain what you would see when a few cm3 of concentrated Na2SO4(aq) were
added to a saturated solution of CaSO4(aq).
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
(d) When a solution of a chromium salt X is electrolysed, chromium metal is deposited on the
cathode, according to the following equation.
Crn+(aq) + ne– → Cr(s)
When a current of 1.8 A was passed for 40 minutes through a solution of salt X, it was found
that 0.776 g of chromium had been deposited.
Calculate the value of n in the above equation. Show your working.
n = ...................... [4]
[Total: 12]
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4
(a) (i) What is meant by the term buffer solution?
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(ii)
Write equations to show how the hydrogencarbonate ion, HCO3–, controls the pH of blood.
.............................................................................................................................................
....................................................................................................................................... [2]
(iii)
A solution containing both Na2HPO4 and NaH2PO4 is commonly used as a buffer solution.
The following equilibrium is present in the solution.
H2PO4–(aq)
HPO42–(aq) + H+(aq)
Ka = 6.2 × 10–8 mol dm–3
Calculate the pH of a buffer solution made by mixing 100 cm3 of 0.5 mol dm–3 Na2HPO4 and
100 cm3 of 0.3 mol dm–3 NaH2PO4.
pH = ........................ [2]
(b) Silver phosphate, Ag3PO4, is sparingly soluble in water.
(i)
Write an expression for the solubility product, Ksp, of Ag3PO4, and state its units.
Ksp =
(ii)
units: .............................. [1]
The numerical value of Ksp is 1.25 × 10–20 at 298 K. Use this value to calculate [Ag+(aq)] in
a saturated solution of Ag3PO4.
[Ag+(aq)] = ............................................... mol dm–3 [3]
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(c) The half-equation for the redox reaction between phosphoric(III) acid and phosphoric(V) acid is
shown.
H3PO4(aq) + 2H+(aq) + 2e–
H3PO3(aq) + H2O(l)
E o = –0.28 V
Find suitable data from the Data Booklet to write an equation for the reaction between H3PO3
and Fe3+(aq) ions, and calculate the
for the reaction.
equation: ....................................................................................................................................
= ..................... V [2]
[Total: 12]
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5
(a) Compound B is a component of several perfumes and flavourings. It can be obtained by the
hydrogenation of compound A.
During the reaction, the hydrogen atoms all add onto the same side of the benzene ring.
+ 6[H]
OH
A
(i)
OH
B
Suggest reagents and conditions for this reaction.
....................................................................................................................................... [1]
(ii)
Circle all the chiral atoms on the structure of B above.
[1]
(iii)
How many possible optical isomers are there with the same structural formula as B?
....................................................................................................................................... [1]
(iv)
Complete the following part-structure to show the structure of one of the isomers of B that
would be formed during the above reaction.
[1]
(b) Compound A can be obtained from propan-2-ylbenzene by the following route.
step 1
propan-2-ylbenzene
step 2
NO2
NH2
step 3
step 4
heat in water
OH
A
(i)
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C
Suggest the structure of the intermediate cation C and draw it in the box above.
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9
(ii)
Suggest reagents and conditions for the following steps.
step 1 ..................................................................................................................................
step 2 ..................................................................................................................................
step 3 ..................................................................................................................................
[4]
(c) Suggest the structures of the organic products of the reactions between each of the compounds
A and B and the following reagents. If no reaction occurs write ‘no reaction’ in the relevant box.
product with A,
product with B,
reagent
OH
OH
HBr
Na
NaOH(aq)
[5]
[Total: 14]
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6
(a) Carboxylic acids can be converted into primary amines by the following sequence of reactions.
RCO2H
step 1
step 2
RCONH2
step 3
RCH2NH2
D
(i)
Suggest the identity of intermediate D and write its structure in the box above.
(ii)
Suggest the reagents for
[1]
step 1 ..................................................................................................................................
step 2 ..................................................................................................................................
step 3 ..................................................................................................................................
[2]
(b) Four compounds, E, F, G and H, are isomers of each other.
Each compound contains an aromatic ring and two functional groups from the following list.
•
•
•
•
•
•
(i)
alcohol
amide
amine
carboxylic acid
ester
phenol
Which of these functional groups react readily with cold HCl (aq)?
....................................................................................................................................... [1]
(ii)
Which of these functional groups react readily with cold NaOH(aq)?
....................................................................................................................................... [1]
The molecular formula of the four isomers, E, F, G and H, is C8H9NO2. All four compounds are
insoluble in water. Table 1 shows their solubilities in acid or alkali.
compound
solubility in HCl (aq)
solubility in NaOH(aq)
E
insoluble
insoluble
F
soluble
soluble
G
soluble
insoluble
H
insoluble
soluble
Table 1
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(iii)
Use this information to suggest the two functional groups, taken from the list on page 10,
that each compound contains.
compound
first functional group
second functional group
E
F
G
H
[4]
(iv)
Suggest a structure for each compound.
E
F
G
H
[4]
[Total: 13]
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12
Section B
Answer all the questions in the spaces provided.
7
This question is about the structures and roles of DNA and RNA in protein synthesis.
(a) Study the structures of the three molecules below.
One of the molecules could be a building block for a protein while the other two could be
building blocks for other biological polymers.
J
K
L
CH2OH
HO
OH
O
H
H
OH
H
H
O
OH
H
OH H
H
H
O
OH
H
HO
H
HO
NH2
OH
Which of the three could be a building block for a protein? Explain your answer.
.............................................................................................................................................
....................................................................................................................................... [1]
(b) Outline the different roles played by mRNA and tRNA in producing a protein with a specific
primary structure.
mRNA ........................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
tRNA ..........................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
[4]
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(c) Sickle cell anaemia is a genetic-based disease in which one of the glutamic acid residues is
replaced by a valine residue.
O
O
O
HO
OH
NH2
OH
NH2
valine
glutamic acid
Suggest and explain how this change in the primary structure of the protein would affect the
overall structure and function of the protein.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
[Total: 8]
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8
(a) NMR spectroscopy and X-ray crystallography can both be used to examine the structure of
organic compounds.
NMR is very useful at examining hydrogen atoms in compounds, but hydrogen atoms are
invisible to X-rays.
(i)
Explain why NMR spectroscopy can detect hydrogen atoms in molecules.
.............................................................................................................................................
....................................................................................................................................... [1]
(ii)
Explain why hydrogen atoms are invisible to X-rays.
.............................................................................................................................................
....................................................................................................................................... [1]
(iii)
The molecular formula of the amino acid cysteine is C3H7O2NS.
Explain which of the atoms present would show the greatest absorption on exposure to
X-rays.
.............................................................................................................................................
....................................................................................................................................... [1]
(b) The NMR spectrum below was obtained from an organic liquid, P, which contains five carbon
atoms per molecule.
9
2
1
10
(i)
9
8
7
6
5
4
δ / ppm
3
2
1
0
How many protons are present in one molecule of P? Explain your answer.
number of protons ............................
.............................................................................................................................................
....................................................................................................................................... [1]
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(ii)
When a little D2O is added to P, the absorption at δ 2.0 disappears.
Explain what this tells you about the group responsible for this absorption and why.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(iii)
What does the absorption at δ 0.9 tell you about the adjacent carbon atom?
.............................................................................................................................................
....................................................................................................................................... [1]
(iv)
What group(s) is/are responsible for the absorption at δ 0.9?
....................................................................................................................................... [1]
(v)
Suggest a structure for P.
[1]
(c) When an isomer of P is heated with concentrated H2SO4 it forms a new compound, Q. This
new compound Q reacts with bromine to give a dibromide, R.
(i)
A mass spectrum was obtained of R. The ratio of the heights of the M : M+1 peaks
was 9.3 : 0.5.
Show that there are five carbon atoms present in one molecule of R.
[1]
(ii)
Predict the ratio of the heights of the M : M+2 : M+4 peaks as a result of the two bromine
atoms in the dibromide R. Show your working.
ratio ...................................... [1]
(iii)
What is the molecular formula of R?
....................................................................................................................................... [1]
[Total: 12]
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9
Polymers consist of monomers joined either by addition or condensation reactions.
(a) Complete the table by placing a tick () in the correct column to indicate the type of reaction
that would polymerise each of the monomers.
monomer
H
H
N
condensation
both
O
C
H
addition
C
OH
H
OH
H
C
C
H
H
H
CH3
C
H 3C
C
H
[3]
(b) Poly(ethene) bags pollute the environment for a long time because they are non-biodegradable.
Suggest why.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
(c) There has been considerable research into making biodegradable plastic bags. The repeat
unit for one of the polymers used, polylactic acid (PLA), is shown.
O
O
CH3
(i)
n
Draw the structure of the monomer for PLA.
[1]
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(ii)
Suggest why PLA breaks down more easily in the environment than poly(ethene).
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [1]
(d) The table shows the melting points of three polymers.
polymer
melting point / °C
polyethene
137
polychloroethene (PVC)
212
nylon 6,6
265
Explain the differences in melting point of these three polymers in terms of the intermolecular
forces between the chains.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
[Total: 10]
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Section A
Answer all the questions in the spaces provided.
1
(a)Calcium has atomic number 20.
Complete the electronic structures for a
calcium atom,
1s22s22p6.................................
calcium ion in the +2 oxidation state.
1s22s22p6.................................
[1]
(b)Calcium nitrate, Ca(NO3)2, is used in fertilisers and can be prepared by an acid-base reaction.
Write an equation for the preparation of calcium nitrate by an acid-base reaction.
.............................................................................................................................................. [1]
(c) (i)When anhydrous calcium nitrate is heated strongly, it decomposes to leave a white solid.
Identify this white solid and suggest another observation for this reaction.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)The ease of thermal decomposition of the Group II nitrates decreases down the group.
Explain this trend.
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [2]
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(d) (i)What is meant by the term standard enthalpy change of hydration,
?
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [2]
(ii)Use the following data to calculate the lattice energy,
You may find it helpful to construct an energy cycle.
enthalpy change
, of calcium nitrate, Ca(NO3)2(s).
value
(Ca2+(g))
–1650 kJ mol–1
(NO3–(g))
–314 kJ mol–1
enthalpy change of solution for Ca(NO3)2(s)
–19 kJ mol–1
Ca(NO3)2(s) = ........................... kJ mol–1 [3]
(e)The standard enthalpy change of hydration for Ba2+,
Suggest an explanation for why the
the Ca2+ ion.
(Ba2+(g)), is –1305 kJ mol–1.
of the Ba2+ ion is less exothermic than the
of
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
[Total: 12]
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4
2
(a)Complete the table to show the number of unpaired electrons in the outer shell of each of the
gaseous atoms, Na to Ar.
Na
Mg
Al
Si
P
S
Cl
Ar
number of
unpaired electrons
[3]
(b) (i)Complete the table for the reactions of two Period 3 chlorides with water.
Period 3 chloride
observations
pH of solution formed
SiCl 4
PCl 5
[3]
(ii)Write an equation for the reaction between SiCl 4 and H2O.
. ...................................................................................................................................... [1]
[Total: 7]
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3The transition element iron is the most abundant element in the Earth’s core.
(a)What is meant by the term transition element?
....................................................................................................................................................
.............................................................................................................................................. [1]
(b)In aqueous solution, iron can form complex ions which contain ligands.
(i)Name the type of bonding that occurs between a ligand and a transition element.
. ...................................................................................................................................... [1]
(ii)Which of the following species can act as a ligand?
Complete the table by placing a tick () in the appropriate column to indicate whether the
species can act as a ligand or not.
species
can act
as a ligand
cannot act
as a ligand
NO3–
BF3
H2NCH2CH2NH2
NH4+
[2]
(c)Manganese ions, Mn2+(aq), show some similar chemical properties to those of copper(II) ions,
Cu2+(aq).
Use this information and the Data Booklet to suggest the formula of the manganese species
formed in each of the following reactions. State the type of reaction taking place in each case.
formula of manganese
species formed
type of
reaction
Mn2+(aq) + NaOH(aq)
Mn2+(aq) + concentrated HCl
Mn2+(aq) + H2O2(aq)
[5]
[Total: 9]
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4In aqueous solution, 2-chloro-2-methylpropane, (CH3)3CCl, reacts with sodium hydroxide, NaOH.
This is a nucleophilic substitution reaction.
(CH3)3CCl (aq) + NaOH(aq) → (CH3)3COH(aq) + NaCl (aq)
(a)Show the mechanism for this reaction. Include all necessary curly arrows, lone pairs and
relevant dipoles.
[3]
The rate of this reaction was investigated using a large excess of sodium hydroxide.
(b)The graph below shows the results of the experiment.
0.60
0.50
0.40
[(CH3)3CCl ]
0.30
/ mol dm–3
0.20
0.10
0
0
20
40
60
80
time / s
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100
120
140
160
7
The reaction is first order with respect to [(CH3)3CCl ]. This can be confirmed from the graph
using half-lives.
(i)What is meant by the half-life of a reaction?
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)Calculate the half-life for this reaction. Show all your working and show clearly any
construction lines on the graph.
[1]
(iii)What would be the effect on the half-life of this reaction if the initial concentration of
[(CH3)3CCl ] was doubled?
. ...................................................................................................................................... [1]
(c) (i)Use the graph in (b) to determine the rate of reaction at 80 s.
Show all your working.
rate = ............................. units ............................. [2]
The rate equation for this reaction is shown.
rate = k [(CH3)3CCl ]
(ii)Calculate the value of the rate constant, k, for this reaction and give its units.
k = ............................. units ............................. [1]
[Total: 9]
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8
5X is a metallic element.
(a) (i)Draw a fully labelled diagram to show how the standard electrode potential, E o, of
X2+(aq) / X(s) could be measured.
[4]
(ii)What are the conditions needed for the value measured to be a standard electrode
potential?
. ...................................................................................................................................... [1]
(iii)State the charge carriers that transfer current through
the solutions, .............................
© UCLES 2015
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[1]
9
(b)An electrochemical cell was set up consisting of an X2+(aq) / X(s) half-cell (E o = –0.40 V) and
an Ag+(aq) / Ag(s) half-cell (E o = +0.80 V).
(i)Write an equation for the reaction that would take place if the electrodes of this cell were
connected by a wire.
. ...................................................................................................................................... [1]
When the current was allowed to pass for a period of time,
•
•
the Ag electrode gained 1.30 g in mass,
the electrode made of metal X lost 0.67 g in mass.
(ii)Calculate the Ar of metal X; hence suggest an identity for X.
Show all your working. Use of the Data Booklet is relevant to this question.
Ar = ...........................
X is ...........................
[4]
[Total: 11]
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6Boron forms many useful compounds.
(a)The compound diborane, B2H6, can be used as a rocket fuel.
It can be prepared by the reaction of boron trifluoride, BF3, with sodium borohydride, NaBH4.
Balance this equation.
.......BF3 + .......NaBH4 → .......B2H6 + .......NaBF4
[1]
(b)Primary and secondary alcohols can be formed by the reaction of carbonyl compounds with
NaBH4, which is a source of hydride ions, H–.
Complete the mechanism for the reaction of butanone with hydride ions, H–, and draw the
intermediate in the box. Include all necessary curly arrows and relevant dipoles.
O
H 3C
C
OH
step 1
H+
H3C
CH2CH3
C
CH2CH3
H
H–
intermediate
[3]
(c)Borane, BH3, is used to synthesise alcohols from alkenes.
The reaction occurs in two steps.
The BH2 group from BH3 bonds to the least substituted carbon atom of the double bond, and
the remaining H from BH3 bonds to the other carbon.
CH3
C
CH3
H
+ BH3
C
CH3
step 1
CH3 H
H
C
C
CH3 CH3
BH2
[O]
CH3 H
H
C
C
OH
CH3 CH3
(i)Suggest the type of reaction in step 1.
. ...................................................................................................................................... [1]
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(ii)The diol Y can be prepared by the same method.
CH3
OH
H 3C
CH3
OH
CH3
Y
Draw the structure of the diene which could be used to prepare diol Y.
[1]
(d)Benzene, C6H6, and borazine, B3N3H6, have planar, cyclic structures.
(i)Describe the structure of and bonding in benzene, C6H6.
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [3]
(ii)In borazine, B3N3H6, the boron and nitrogen atoms alternate around the ring. Each ring
atom has a single hydrogen atom bonded to it.
All boron-nitrogen bonds in borazine are 0.144 nm in length, whereas in simple compounds
B–N and B=N bond lengths are 0.154 nm and 0.136 nm respectively.
Suggest and draw the structure of borazine.
[1]
[Total: 10]
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7
(a)Sunset Yellow is a yellow colouring agent used in food and drinks, which can be made by the
following route.
In step 3 of this synthesis, a phenol-like compound, S, reacts with intermediate T made from
amine R.
Assume that the –SO3– Na+ group does not react.
O2N
SO3– Na+
step 1
Q
R (C6H6NSO3Na)
step 2
+
S
T
step 3
NaOH(aq)
OH
N
N
SO3– Na+
Na+ –O3S
Sunset Yellow
(i)Suggest structures for compounds R, S and T and draw them in the boxes above.
[3]
(ii)Suggest reagents and conditions for
step 1, . ................................................................................................................................
step 2. . ................................................................................................................................
[3]
(iii)What type of organic salt is formed in step 2?
. ...................................................................................................................................... [1]
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(b)Compound W has the following structure.
NH2
H 2N
O
(i)How many σ and π bonds are present in a molecule of W?
σ bonds ....................... π bonds .......................
[2]
(ii)The products of the reactions of W with cold HCl and with CH3CH2Br are soluble in water
but not in organic solvents.
Complete the table for these reactions of W.
reagent
structure of product
(molecular formula given)
type of reaction
HCl
(C4H9N2OCl )
CH3CH2Br
(C6H13N2BrO)
[3]
[Total: 12]
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Section B
Answer all the questions in the spaces provided.
8
(a)The sequence of bases in DNA is a code for the order of amino acids in the primary structure
of proteins.
The diagram represents the stages involved in the formation of a protein from DNA.
stage 1
stage 2
A
DNA
stage 3
ribosome
protein
B1
B2
etc.
(i)Identify the biochemical structures, A and B1, B2 etc.
biochemical structure
identity
A
B1, B2 etc.
[2]
(ii)Name the biochemical processes involved in stages 1 and 3.
process
name of
biochemical process
stage 1
stage 3
[1]
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(b)Adenine is an integral part of DNA.
NH2
N
N
N
H
N
adenine
(i)State the molecular formula of adenine.
. ...................................................................................................................................... [1]
(ii)Identify the three other nitrogenous bases in DNA.
.....................................
.....................................
..................................... [1]
(iii)DNA has a double helical structure that consists of two strands linked together.
What type of bonding exists between the
phosphate and sugar groups within a DNA strand, .............................................................
different bases on the two strands? . ...................................................................................
[2]
(c)The breakdown of adenosine triphosphate, ATP, provides the energy for many cellular reactions.
ATP + H2O → ADP + Pi
What type of chemical reaction is this?
.............................................................................................................................................. [1]
(d)X-ray crystallography can be useful in obtaining information about the structures of large
organic molecules, such as ATP. The technique involves X-rays interacting with the electrons
within the molecule.
(i)Which element in the molecule of ATP will interact most strongly with the X-ray beam?
. ...................................................................................................................................... [1]
(ii)Explain why X-ray crystallography will not detect hydrogen atoms.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
[Total: 10]
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9
(a)Some metals are essential to biochemical processes.
Complete the following table naming one metal in each case.
biochemical process
metal
haemoglobin in oxygen transport
transmission of nerve impulses
enzyme cofactor
[2]
(b)Enzymes are a special type of protein molecule that catalyse biochemical reactions.
Explain briefly the mechanism by which an enzyme breaks down a substrate molecule.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
(c)Disulfide bonds play an important role in the stability of some proteins such as the keratin in
human hair.
The amino acid involved in the formation of a disulfide bond is cysteine, H2NCH(CH2SH)CO2H.
(i)At which level of protein structure (primary, secondary, tertiary) are disulfide bonds formed?
. ...................................................................................................................................... [1]
(ii)Use a functional group in cysteine to show how disulfide bonds are formed.
[1]
(iii)What type of chemical reaction is this?
. ...................................................................................................................................... [1]
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(d)The NMR spectrum of cysteine, H2NCH(CH2SH)CO2H, shows five absorptions.
After shaking a solution of cysteine with a few drops of D2O, the NMR spectrum shows only
two absorptions, E and F, shown below.
E
F
(i)Identify the two types of protons responsible for the absorptions E and F.
E ..........................................................................................................................................
F...........................................................................................................................................
[1]
(ii)State and explain the splitting patterns of the absorptions E and F.
E ..........................................................................................................................................
. ............................................................................................................................................
F ..........................................................................................................................................
. ...................................................................................................................................... [2]
[Total: 11]
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10 (a)Aspartame is an artificial sweetener that has the structure shown below.
O
H3C
O
O
N
H
OH
NH2
O
aspartame
(i)Draw a circle around each chiral centre in aspartame.
[1]
In the stomach, aspartame is hydrolysed by acid to form three organic products.
(ii)On the diagram above, use arrows to indicate the two bonds that would be hydrolysed in
the stomach.
[2]
(iii)Draw the structures of the three products formed after complete acid hydrolysis of
aspartame.
[3]
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(b)Aspartame is soluble in water.
By referring to the structure of aspartame, explain why it is soluble in water.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
(c)Recently, nanotechnology has been involved in the development of a new natural sweetener,
Nano Sugar, extracted from sugar cane.
What is the approximate width of a nanoparticle?
.............................................................................................................................................. [1]
[Total: 9]
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Section A
Answer all the questions in the spaces provided.
1
(a)The dissolving of an ionic compound in water is accompanied by an energy change, the
enthalpy change of solution, ∆H sol.
MgCl 2(s) + aq → Mg2+(aq) + 2Cl –(aq)
Describe, in terms of bond breaking and bond making, what happens to the solid ionic lattice
when an ionic compound dissolves in water.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
(b) (i) What is meant by the term enthalpy change of solution, ∆H sol?
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)Use the following data to calculate the standard enthalpy change of hydration,
chloride ions, Cl –(g).
You may find it helpful to construct an energy cycle.
enthalpy change
(Mg2+(g))
, of
value
–1925 kJ mol–1
lattice energy of MgCl 2(s)
enthalpy change of solution for MgCl 2(s)
–2524 kJ mol–1
–155 kJ mol–1
(Cl –(g)) = ......................... kJ mol–1 [2]
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(iii)The enthalpy change of hydration for Na+,
Suggest an explanation for why the
of the Mg2+ ion.
(Na+(g)), is –410 kJ mol–1.
of the Na+ ion is less exothermic than the
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [2]
(c)Describe and explain how the solubility of the Group II sulfates varies down the group.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [4]
[Total: 11]
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2
(a)Cobalt is a transition element and forms compounds with oxidation numbers +2 and +3.
Complete the electronic structures for
a cobalt atom,
1s22s22p6.................................
cobalt in the +3 oxidation state.
1s22s22p6.................................
[2]
(b) (i)In an aqueous solution of cobalt(II) sulfate the cobalt forms complex ions.
What is meant by the term complex ion?
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)State two chemical properties of cobalt, other than the formation of complexes, that are
not shown by a typical s-block element.
. ............................................................................................................................................
. ...................................................................................................................................... [2]
(c)Cobalt(II) ions, Co2+(aq), show some chemical properties similar to those of copper(II) ions,
Cu2+(aq).
Use this information and the Data Booklet to suggest the formula of the cobalt species formed
in each of the following reactions. State the type of reaction taking place in each case.
formula of cobalt
species formed
type of reaction
Co2+(aq) + an excess of NH3(aq)
Co2+(aq) + OH–(aq)
Co2+(aq) + S2O82–(aq)
[5]
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(d)Some transition elements are present in superconductors. These are materials that conduct
electricity with little or no resistance.
Compound Q is a superconductor and contains 13.4% yttrium, 41.2% barium, 28.6% copper
and 16.8% oxygen by mass.
(i)Show that the empirical formula of Q is YBa2Cu3O7. Show all your working.
[1]
(ii)The table shows the oxidation numbers of yttrium, barium and oxygen in Q.
element
oxidation number
yttrium
+3
barium
+2
oxygen
–2
Calculate the average oxidation number of copper in Q.
[1]
(iii)Hence deduce the oxidation number of each of the three copper atoms in Q.
[1]
[Total: 13]
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3Chlorine gas and iron(II) ions react together in aqueous solution as shown.
Cl 2(g) + 2Fe2+(aq) → 2Cl –(aq) + 2Fe3+(aq)
(a) (i)Complete and label the diagram to show how the standard cell potential,
above reaction could be measured at standard conditions.
, for the
[4]
(ii)Use the Data Booklet to calculate the
for this reaction.
[1]
(b)What colour change would you see when chlorine gas is bubbled through a solution containing
Fe2+(aq) ions until the reaction is complete?
.............................................................................................................................................. [1]
(c)Predict the effect, if any, of decreasing the concentration of Cl –(aq) on the magnitude of the
cell potential in (a)(ii). Explain your answer.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
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(d) (i)A fuel cell is an electrochemical cell that can be used to generate electrical energy.
In the alkaline hydrogen-oxygen fuel cell, H2(g) and O2(g) are passed over two inert
electrodes immersed in an alkaline solution.
Write the half-equations for the reactions taking place at each of these electrodes.
hydrogen electrode . ............................................................................................................
oxygen electrode .................................................................................................................
[2]
(ii)Construct an equation for the overall reaction.
. ...................................................................................................................................... [1]
(iii)Suggest one possible advantage of using a hydrogen-oxygen fuel cell over a conventional
‘simple cell’ battery.
. ...................................................................................................................................... [1]
[Total: 12]
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4 (a) (i)On the grid below, sketch the trend in the melting points of the Group IV elements.
The point for germanium has already been shown.
melting
point
C
Si
Ge
Sn
Pb
[1]
(ii)Suggest an explanation of this trend in terms of structure and bonding of the Group IV
elements.
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(b)GeO2, SnO2 and PbO2 are amphoteric oxides.
(i)What is meant by the term amphoteric?
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)Construct an equation for the reaction of SnO2 with NaOH.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(c) (i)By quoting information from the Data Booklet explain why the reaction between
Cr2O72–(aq) ions and acidified Sn2+(aq) ions is feasible.
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [1]
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(ii)Construct an equation for the reaction in (c)(i) and give any relevant observations.
equation . .............................................................................................................................
observations ........................................................................................................................
. ...................................................................................................................................... [2]
(d) (i)On heating, germanium(II) oxide disproportionates to form germanium(IV) oxide and
germanium.
Describe, using this reaction as an example, what is meant by a disproportionation
reaction.
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)Some of the reactions of cyanogen, NC–CN, are similar to those of chlorine, Cl –Cl.
On treatment with cold, aqueous sodium hydroxide, cyanogen disproportionates in a
similar manner to chlorine.
Complete the equation for this reaction.
(CN)2 + ........NaOH → .............. + .............. + ..............
[1]
(iii)Draw a ‘dot-and-cross’ diagram for NC–CN. Show the outer electrons only.
[1]
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(e)At room temperature, phosphorus atoms form P4 molecules rather than P2 molecules.
The phosphorus molecule, P4, has a cage-like structure containing only P–P single bonds.
All the phosphorus atoms in P4 are trivalent.
(i)Suggest a structure for P4.
[1]
(ii)At a temperature of 1200 K P2 and P4 exist in equilibrium in the gas phase.
P2 molecules contain the P≡P bond.
The average bond energy of P–P is 198 kJ mol–1 while that of P≡P is 489 kJ mol–1.
Use the above bond energies to calculate the enthalpy change, ∆H, for the following
reaction.
2P2(g) → P4(g)
[2]
(f)When phosphorus(V) chloride, PCl 5, is reacted with ammonium chloride, NH4Cl, hydrogen
chloride gas, HCl, is released and a product with the molecular formula P3N3Cl 6 is formed.
(i)Construct an equation for this reaction.
. ...................................................................................................................................... [1]
(ii)P3N3Cl 6 has a cyclic structure containing alternating phosphorus and nitrogen atoms in
the ring system. All the nitrogen atoms are trivalent and all the phosphorus atoms are
pentavalent.
Suggest a structure for P3N3Cl 6.
[1]
[Total: 15]
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5
(a)A student carries out some reactions with separate samples of butanal and butanone.
O
O
H
butanal
butanone
The following results are obtained with reagents L, M and N.
( means a reaction takes place.)
reagent
butanal
butanone
L


M

no reaction
N
no reaction

(i)Suggest a possible identity for each reagent L, M and N.
L ..........................................................................................................................................
M . ........................................................................................................................................
N ..........................................................................................................................................
[3]
(ii)Give the structure of the organic product formed when M reacts with butanal.
[1]
(iii)What is observed when N reacts with butanone?
. ...................................................................................................................................... [1]
(iv) What type of reaction is occurring when N reacts with butanone?
. ...................................................................................................................................... [1]
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(b)The organolithium compound methyl lithium, CH3Li, can act as a source of CH3– ions.
CH3Li
CH3– + Li+
The CH3– ion can act as a nucleophile.
The reaction between methyl lithium and carbonyl compounds can be used to make alcohols.
(i)Suggest a mechanism for the reaction of butanal with CH3– ions. Include all necessary
curly arrows, lone pairs and relevant dipoles.
OH
O
C
H
CH2CH2CH3
step 1
H
+
H
C
CH2CH2CH3
CH3
CH3–
intermediate
[3]
(ii)A chemist decides to prepare the following organic compound G from butanal.
OH
CH3
H3C
CH3
G
Draw the structure of the organolithium reagent which could be used to prepare G from
butanal.
[1]
[Total: 10]
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14
64-nitrophenol can be converted into a range of useful organic products.
O2N
OH
4-nitrophenol
(a)4-nitrophenol can react with three different reagents.
Complete the table by:
•
•
drawing the structures of the organic products formed,
identifying the non-organic products formed.
reagent
organic product structure
identity of
non-organic product
Na(s)
Br2(aq)
CH3COCl (l)
[4]
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(b)4-nitrophenol can also be used in the synthesis of the dye Mordant Brown by the following
route.
In step 2 of this synthesis, 4-nitrophenol reacts with intermediate F made from amine E.
Assume that the –SO3– Na+ group does not react.
E (C6H8N3SO3Na)
step 1
OH
+
F
NO2
step 2
H 2N
NH2
OH
N
NO2
N
SO3– Na+
Mordant Brown
(i)Suggest structures for compounds E and F and draw them in the boxes above.
[2]
(ii)Suggest reagents and conditions for
step 1, . ................................................................................................................................
step 2. . ................................................................................................................................
[3]
[Total: 9]
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Section B
Answer all the questions in the spaces provided.
7DNA is an important biochemical molecule.
(a)DNA has a double helical structure that consists of two strands linked together.
Draw a block diagram of DNA showing two repeat units in each strand.
Label all the components, showing and labelling the bonds between the strands.
[5]
(b)Genetic information is stored in DNA.
Outline the main steps in the replication of DNA.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
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(c)DNA fingerprinting is based on the fact that all humans (apart from genetically identical twins)
have different DNA base sequences. This is regularly used to help investigate serious crimes.
(i)The first stage of DNA fingerprinting requires a sample of DNA to be broken down into
shorter fragments.
What could be used to carry out this fragmentation?
. ...................................................................................................................................... [1]
(ii)Name the analytical technique used to separate these short fragments.
. ...................................................................................................................................... [1]
(iii)After the fragments have been separated, what could the DNA fingerprint be treated with
to reveal the position of the bands?
. ...................................................................................................................................... [1]
(iv)A sample of blood, thought to be from the suspect, was found at a crime scene. The DNA
of the blood sample, and that of four possible suspects, was analysed.
blood
stain
suspect suspect suspect suspect
1
2
3
4
Based on this evidence, circle the suspect who should be arrested.
suspect 1
suspect 2
suspect 3
suspect 4
[1]
[Total: 11]
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8 (a)A mixture of volatile organic compounds X, Y and Z can be separated in a gas chromatograph.
Their identities can be confirmed by measuring their different retention times and comparing to
known values.
A gas chromatogram is shown.
Y
absorption
X
5
Z
10
15
20
time / mins
(i)Suggest what is meant by the term retention time.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)Give an example of a carrier gas used in gas chromatography.
. ...................................................................................................................................... [1]
(iii)Z spends the longest time in the chromatography column.
Suggest why this might be the case.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(iv)Explain a possible limitation of gas / liquid chromatography in separating two esters such
as ethyl methanoate, HCO2CH2CH3, and methyl ethanoate, CH3CO2CH3.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(v)A student works out the areas underneath the three peaks in the chromatogram.
peak
X
Y
Z
area / mm2
22
38
16
Assuming the areas underneath the peaks are proportional to the masses of the respective
components, what percentage of the original mixture was made up of the organic
compound, X?
% of X = ........................ [1]
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(b)The NMR spectrum of Y given below shows four absorptions.
absorption
4
3
2
δ / ppm
1
0
(i)What compound is responsible for the absorption at δ = 0?
. ...................................................................................................................................... [1]
(ii)Compound Y is an ester with the molecular formula C4H8O2.
Complete the table for the NMR spectrum of Y.
The actual chemical shifts for three absorptions in Y and the splitting pattern for the
resonance at δ = 3.7 ppm have been given for you.
Use of the Data Booklet may be helpful.
chemical shift
δ / ppm
type of proton(s)
number of protons
splitting pattern
1.0
2.3
3.7
singlet
[4]
(iii)Use your conclusions to suggest a structure for the ester Y.
[1]
[Total: 11]
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9Prodrugs are compounds that are inactive, but are easily converted in the body to the active drug
by enzyme hydrolysis.
Compound W is a prodrug.
CH3 O
H 2N
NH2
O
O
W
(a)Complete the molecular formula for W.
C H34N O
[1]
(b)Compound W contains a benzene ring in its structure.
Name three other functional groups in W.
..........................................
..........................................
.......................................... [2]
(c) (i)On the diagram above, use an arrow to indicate the bond that would be hydrolysed.
[1]
(ii)Draw the structures of the likely products of the enzyme hydrolysis of compound W.
[2]
(d)What features of the molecule W make it water soluble? Explain your answer.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
[Total: 8]
To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International
Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after
the live examination series.
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Answer all the questions in the spaces provided.
1
(a)Limewater is a saturated solution of Ca(OH)2 in water. It is used to test for the presence of CO2
in a gaseous mixture.
(i)Write an equation for the reaction between limewater and CO2.
. ...................................................................................................................................... [1]
A saturated solution of Ba(OH)2 can be used instead of Ca(OH)2 to test for CO2. A saturated
solution of Mg(OH)2 cannot be used for this test.
(ii)Explain why a saturated solution of Ba(OH)2 can be used to test for CO2.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(iii)Explain why a saturated solution of Mg(OH)2 cannot be used to test for CO2.
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [2]
(b)Describe and explain the trend in the thermal stabilities of the carbonates down Group 2.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
(c)Nickel carbonate, NiCO3, decomposes on heating.
Use the Data Booklet to explain whether NiCO3 will decompose more or less readily than
CaCO3.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
[Total: 9]
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2
(a) (i)Complete the following electronic configurations.
•the cobalt atom, Co
•
the cobalt(II) ion, Co2+
1s22s22p6 .........................................
1s22s22p6 .........................................
[1]
(ii)State the colours you would observe when concentrated HCl (aq) is added to an aqueous
solution of cobalt(II) nitrate, Co(NO3)2.
Give the formulae and geometry of the complexes formed.
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [5]
(b)There are two isomers with the formula Ni(R3P)2I2, but only one structure with the formula
Co(R3P)2I2. (R = alkyl, R3P is a monodentate ligand)
Draw diagrams showing the structure of Co(R3P)2I2 and the two isomers of Ni(R3P)2I2.
Ni(R3P)2I2
Ni(R3P)2I2
Co(R3P)2I2
[3]
[Total: 9]
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4
3One method of producing hydrogen from natural gas is the reaction between hydrogen sulfide and
methane.
2H2S(g) + CH4(g)
CS2(g) + 4H2(g)
(a)Write the expression for Kp for this reaction, and state its units.
Kp =
units .............................
[2]
(b)The initial partial pressures of the two gases in a mixture at 1000 K are recorded.
H2S(g) 200 atm
CH4(g) 100 atm
The mixture is left to reach equilibrium.
It is found that the equilibrium partial pressure of CS2(g) is 2 atm and that of the remaining
CH4(g) is 98 atm.
(i)Calculate the equilibrium partial pressures of H2S(g) and H2(g).
p(H2S) = ............................. atm
p(H2) = ............................. atm
[2]
(ii)Calculate the value of Kp at this temperature.
Kp = ............................. [1]
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(c) (i)Predict the sign of ∆S o for this reaction. Explain your answer.
2H2S(g) + CH4(g)
CS2(g) + 4H2(g)
∆H o = +241 kJ mol–1
. ............................................................................................................................................
. ...................................................................................................................................... [1]
The free energy change, ∆G o, for this reaction at 1000 K is +51 kJ mol–1.
(ii)Calculate the value of ∆S o for this reaction, stating its units.
∆S o = ............................. units ............................. [2]
(d)How would the value of ∆G o, and hence the spontaneity (feasibility) of this reaction change as
the temperature increases? Explain your answer.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
[Total: 10]
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4
(a) (i)Define the term standard cell potential,
.
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [1]
The following incomplete diagram shows the apparatus that can be used to measure the
for a cell composed of the Fe3+ / Fe2+ and Ag+ / Ag half-cells.
A
C
B
D
(ii)Complete the diagram, labelling the components you add.
[1]
(iii)Identify the components A-D.
A ..........................................................................................................................................
B ..........................................................................................................................................
C ..........................................................................................................................................
D ..........................................................................................................................................
[3]
(b) (i)Use E o values to write an equation for the cell reaction that takes place if the two electrodes
in (a) are connected by a wire and the circuit is completed.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)Another electrochemical cell was set up using 0.31 mol dm–3 Ag+(aq) instead of the
standard Ag solution.
Use the Nernst equation, E = E o + 0.059 log [Ag+(aq)], and the relevant E o values to
calculate the new E cell in this experiment.
E cell = .............................. V [2]
[Total: 8]
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5Dicarboxylic acids dissociate in stages.
HO2C(CH2)nCO2H
stage 1
HO2C(CH2)nCO2– + H+
stage 2
–
O2C(CH2)nCO2– + 2H+
(a)The pKa values for stage 1 and stage 2 for some dicarboxylic acids are listed below.
n in HO2C(CH2)nCO2H
pKa(1)
for stage 1
pKa(2)
for stage 2
1
2.83
5.69
2
4.16
5.61
3
4.31
5.41
For comparison, the pKa of ethanoic acid, CH3CO2H, is 4.76.
(i)State the mathematical relationship between pKa and the acid dissociation constant Ka.
. ...................................................................................................................................... [1]
(ii)With reference to the table above, suggest why the pKa(1) values
•are all smaller than the pKa of ethanoic acid,
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
•become larger as n increases.
. ............................................................................................................................................
[3]
(iii)Suggest why all the pKa(2) values in the table above are larger than the pKa of ethanoic
acid.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(b)The monosodium salts of edible dicarboxylic acids are added to some foodstuffs as buffers.
(i)Explain what is meant by the term buffer solution.
. ............................................................................................................................................
. ...................................................................................................................................... [2]
(ii)Write two equations to show how monosodium butanedioate, HO2CCH2CH2CO2Na, acts
as a buffer.
. ............................................................................................................................................
. ...................................................................................................................................... [2]
[Total: 9]
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8
6Nitrobenzene, C6H5NO2, can be reduced to phenylamine, C6H5NH2, in acid solution in a two step
process.
(a) (i)Balance the half-equation for this reaction to work out how many moles of electrons are
needed to reduce one mole of nitrobenzene.
C6H5NO2 + ...........e– + ...........H+ → C6H5NH2 + ...........H2O
[1]
(ii)The reducing agent normally used is granulated tin and concentrated hydrochloric acid.
In the first step, the reduction of nitrobenzene to phenylammonium chloride can be
represented by the equation shown.
Use oxidation numbers or electrons transferred to balance this equation. You might find
your answer to (i) useful.
......C6H5NO2 + ......HCl + ......Sn → ......C6H5NH3Cl + ......SnCl 4 + ......H2O
[2]
(b)When 5.0 g of nitrobenzene was reduced in this reaction, 4.2 g of phenylammonium chloride,
C6H5NH3Cl, was produced.
Calculate the percentage yield.
percentage yield of phenylammonium chloride = ............................. % [2]
(c)Following the reaction in (b), an excess of NaOH(aq) was added to liberate phenylamine from
phenylammonium chloride.
(i)Calculate the mass of phenylamine, C6H5NH2, produced when 4.20 g of phenylammonium
chloride reacts with an excess of NaOH(aq).
mass of phenylamine = ............................. g [1]
The final volume of the alkaline solution of phenylamine in (i) was 25.0 cm3. The phenylamine
was extracted by addition of 50 cm3 of dichloromethane. After the extraction, the dichloromethane
layer contained 2.68 g of phenylamine.
(ii)Use the data to calculate the partition coefficient, K partition, of phenylamine between
dichloromethane and water.
K partition = ............................. [2]
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(d)How does the basicity of phenylamine compare to that of ethylamine? Explain your answer.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
(e)Phenol can be synthesised from phenylamine in two steps.
NH2
OH
step 1
step 2
+ N2
E
(i)State the reagents and conditions for steps 1 and 2.
step 1 . .................................................................................................................................
step 2 . .................................................................................................................................
[2]
(ii)Draw the structure of the intermediate compound E in the box above.
[1]
[Total: 13]
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7
(a) (i)Use the Data Booklet to draw the structure of the tripeptide Ala-Ser-Gly showing its peptide
bonds in full.
Ala-Ser-Gly
[2]
(ii)Calculate the relative molecular mass, Mr, of Ala-Ser-Gly.
Mr = ............................ [1]
(b)Electrophoresis can be used to separate mixtures of amino acids and peptides.
A mixture of the tripeptide Ala-Ser-Gly and its three constituent amino acids was subjected to
electrophoresis in a buffer at pH 11.
(i)Draw the structure of serine at pH 11.
[1]
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11
At the end of the experiment the following results were seen.
F
mixture
applied here
G
H
P
Q
R
S
I
(ii)Identify the components labelled F-I in the above diagram.
F ..........................................................................................................................................
G . ........................................................................................................................................
H ..........................................................................................................................................
I . .........................................................................................................................................
[4]
(iii)Suggest the identities of the species responsible for
spot P, .................................................................................................................................
spot S. .................................................................................................................................
Explain your answers.
. ............................................................................................................................................
. ...................................................................................................................................... [3]
(c) (i)State the reagents and conditions needed for converting the tripeptide into its three
constituent amino acids.
. ...................................................................................................................................... [1]
(ii)Name the type of reaction in (i).
. ...................................................................................................................................... [1]
[Total: 13]
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8
(a)Chromyl chloride, CrO2Cl 2, can be prepared by heating a mixture of potassium dichromate(VI)
and potassium chloride with concentrated sulfuric acid.
K2Cr2O7 + 4KCl + 3H2SO4 → 2CrO2Cl 2 + 3K2SO4 + 3H2O
Use the following data to complete the Hess’ Law cycle and calculate the enthalpy change of
the reaction, ∆Hr.
compound
enthalpy change of
/ kJ mol–1
formation,
K2Cr2O7
–2061
KCl
–437
H2SO4
–814
CrO2Cl 2
–580
K2SO4
–1438
H2O
–286
K2Cr2O7 + 4KCl + 3H2SO4
∆Hr
2CrO2Cl 2 + 3K2SO4 + 3H2O
elements
∆Hr = ............................ kJ mol–1 [2]
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(b)There are two isomeric complex ions with the formula [Cr(NH3)4Cl 2]+. One is green and the
other is violet.
(i)Suggest the type of isomerism shown by these complex ions.
. ...................................................................................................................................... [1]
(ii)Explain why these two complex ions
•are coloured, . ...............................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
•
have different colours. .................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
[4]
[Total: 7]
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9The anti-inflammatory drug ketoprofen can be synthesised from benzene via the following five
steps.
O
step 1
step 2
T, (C15H14O)
O
step 3
Br
step 4
O
CO2H
step 5
ketoprofen
U
(a)Suggest the structures of compounds T and U and draw them in the boxes above.
[2]
(b)Suggest reagents and conditions for steps 1-5.
step 1 . ........................................................................................................................................
step 2 . ........................................................................................................................................
step 3 . ........................................................................................................................................
step 4 . ........................................................................................................................................
step 5 . ........................................................................................................................................
[5]
(c)What types of reaction are steps 1 and 5?
step 1 . ........................................................................................................................................
step 5 . ........................................................................................................................................
[2]
[Total: 9]
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10 (a)Ethanedioic acid, C2O4H2, occurs in many vegetables. The amount that occurs in spinach can
be estimated as follows.
•40.0 g of spinach leaves are crushed and mixed with distilled water, using a mortar and
pestle.
•The mixture is filtered, and the leaves are washed with a little more water.
•The combined filtrate and washings are made up to 100.0 cm3 with water.
•A 25.0 cm3 portion of the resulting solution is added to a conical flask, along with an excess
of dilute sulfuric acid.
•The acidified solution is warmed, and then titrated with 0.0200 mol dm–3 KMnO4.
The equation for the reaction between ethanedioic acid and acidified manganate(VII) ions is
shown.
2MnO4– + 6H+ + 5C2O4H2 → 2Mn2+ + 10CO2 + 8H2O
In the titration, 15.20 cm3 of KMnO4 was required to reach the end-point.
Calculate the percentage by mass of ethanedioic acid in the spinach leaves.
percentage of ethanedioic acid = ............................. % [3]
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(b)Ethanedioic acid can be converted into ethanedioyl chloride:
HO2CCO2H → Cl OCCOCl
(i)State a suitable reagent for this reaction.
. ...................................................................................................................................... [1]
(ii)For the reactions of ethanedioyl chloride below, suggest the structures of compounds J
and K and draw them in the boxes.
CH3OH
COCl
H2NCH2CH2NH2
COCl
J (C4H6O4)
K (C4H6N2O2)
[2]
(c)When ethanedioyl chloride is reacted with silver ethanedioate, AgO2CCO2Ag, in ethoxyethane
at –30 °C, an oxide of carbon, L, is formed. The molecule of L has no overall dipole and has
molecular formula C4O6.
The carbon-13 NMR spectrum of a solution of L in ethoxyethane, CH3CH2OCH2CH3, is shown
below.
150
100
50
0
δ (ppm)
(i)Use the Data Booklet to state in the boxes below the δ values for the peaks in the spectrum
which are due to the carbon atoms in ethoxyethane.
CH3
CH2
O
CH2
CH3
δ values
[2]
(ii)Explain what the rest of the carbon-13 NMR spectrum indicates about the structure of L.
. ...................................................................................................................................... [1]
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(d)When pure L is reacted with an excess of CH3OH, a mixture of three compounds is formed.
L
and
(C4O6)
CH3OH
→
M
and
N
and
O
(C2H2O4)
(C3H4O4)
(C4H6O4)
M is formed as one of the products when either N or O is heated with aqueous acid.
The table gives information of the peaks recorded in the carbon-13 NMR spectra of M, N and O.
compound
peaks recorded in
carbon-13 NMR spectrum
M
δ 162
N
δ 53
O
δ 160
δ 53
δ 162
δ 160
(i)Suggest the structures of M, N and O.
M, (C2H2O4)
N, (C3H4O4)
O, (C4H6O4)
[3]
(ii)Suggest a structure for L that fits all the data given in (c) and (d).
L, (C4O6)
[1]
[Total: 13]
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2
Answer all questions in the spaces provided.
1
(a)Magnesium nitrate, Mg(NO3)2, is very soluble in water. When a hot saturated solution of
magnesium nitrate is cooled, crystals of the hydrate, Mg(NO3)2.6H2O, are formed.
In the crystals, six water molecules bond to each Mg2+ ion, and some of these water molecules
are also bonded to the nitrate ions.
(i)Suggest the type of bonding that occurs between
H2O and Mg2+, . ....................................................................................................................
H2O and NO3–. .....................................................................................................................
[2]
(ii)Describe the arrangement of the water molecules around the Mg2+ ion.
. ...................................................................................................................................... [1]
(iii)Describe in detail what you would observe when crystals of Mg(NO3)2.6H2O are heated in
a boiling tube, gently at first and then more strongly.
Write equations for any reactions that occur.
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [4]
(iv)Calculate the percentage loss in mass when Mg(NO3)2.6H2O is heated strongly to constant
mass.
percentage loss = ............................. % [2]
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(b)Explain why the Group 2 nitrates become more stable to heat down the group.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
(c)Magnesium nitrate and silver nitrate, AgNO3, decompose on heating to produce the same
gases. Silver nitrate also produces silver metal during decomposition.
Write an equation for the decomposition of AgNO3.
.............................................................................................................................................. [1]
[Total: 12]
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2Ethanoic acid is a weak acid.
(a)Explain what is meant by the term weak acid.
....................................................................................................................................................
.............................................................................................................................................. [1]
(b)The pKa values of four acids are listed below.
acid
structural formula
pKa
1
CH3CO2H
4.8
2
CH3CH2CO2H
4.9
3
CH3CHCl CO2H
2.8
4
CH2Cl CH2CO2H
4.0
(i)State the mathematical relationship between pKa and the acid dissociation constant Ka.
. ...................................................................................................................................... [1]
(ii)With reference to acidity, explain the difference in pKa values between
•acid 1 and acid 2,
. ............................................................................................................................................
. ............................................................................................................................................
•
acid 2 and acid 3,
. ............................................................................................................................................
. ............................................................................................................................................
•
acid 3 and acid 4.
. ............................................................................................................................................
. ............................................................................................................................................
[3]
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(c) (i)Draw a fully labelled diagram of the equipment needed to measure the voltage of an
electrochemical cell consisting of the standard hydrogen electrode and the standard
Cu / Cu2+ electrode.
[4]
(ii)For the cell drawn in (i), calculate the
= ......................................
and state which electrode is positive.
identity of the positive electrode .....................................
[1]
(d)A monobasic acid, D, has Ka = 1.23 × 10–5 mol dm–3.
(i)Calculate the pH of a 0.100 mol dm–3 solution of D.
pH = ............................ [2]
(ii)An electrochemical cell similar to the one you have drawn in (c)(i) was set up using a
0.100 mol dm–3 solution of D in the hydrogen electrode instead of the standard solution.
Use the data and the Nernst equation, E = E o + 0.059 log [H+(aq)], to calculate the new E cell
in this experiment.
E cell = ............................ V [2]
[Total: 14]
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3
(a)2-bromopropane can be used to synthesise methylethylamine and 2-methylpropylamine.
NH2
reaction 1
methylethylamine
Br
2-bromopropane
reaction 2
reaction 3
NH2
X
2-methylpropylamine
(i)Draw the structure of the intermediate X in the box above.
[1]
(ii)Suggest reagents and conditions for
•
reaction 1, .....................................................................................................................
•
reaction 2, .....................................................................................................................
•
reaction 3. .....................................................................................................................
[3]
(b) (i)Write an equation showing why aqueous solutions of ethylamine are alkaline.
. ...................................................................................................................................... [1]
(ii)Compare the basicities of ethylamine and ammonia. Explain your answer.
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [2]
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(c)Solutions containing mixtures of amines and their salts are buffer solutions.
(i)Explain what is meant by the term buffer solution.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)Write two equations to show how a solution containing a mixture of CH3NH2 and CH3NH3Cl
acts as a buffer.
. ............................................................................................................................................
. ...................................................................................................................................... [2]
[Total: 10]
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4
(a)There are two isomeric complexes with the formula Pt(NH3)2Cl 2, one of which is an anti-cancer
drug.
(i)Draw diagrams to show the three-dimensional structures of the two isomers.
isomer 1
isomer 2
[2]
(ii)Comment on the polarity of the two isomers of Pt(NH3)2Cl 2. Explain your answer.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
Oxaloplatin is another successful anti-cancer drug in which the stereochemistry around the
platinum atom is the same as that in Pt(NH3)2Cl 2.
NH2
O
Pt
NH2
O
C
C
O
O
oxaloplatin
(iii)Explain why there are no isomers of oxaloplatin.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
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(b)Only one structure of the complex [Ni(R3P)2Cl 2] is known. (R = CH3, R3P is a monodentate ligand)
(i)What does this indicate about the stereochemistry around the nickel atom?
. ...................................................................................................................................... [1]
(ii)Draw a three-dimensional diagram showing the structure of this complex.
[1]
[Total: 6]
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10
5Cadmium ions form complexes with primary amines and with 1,2-diaminoethane.
Cd2+(aq) + 4CH3NH2(aq)
Cd2+(aq) + 2H2NCH2CH2NH2(aq)
[Cd(CH3NH2)4]2+(aq)
Kstab = 3.6 × 106
equilibrium I
[Cd(H2NCH2CH2NH2)2]2+(aq)
Kstab = 4.2 × 1010
equilibrium II
(a) (i)Write an expression for the stability constant, Kstab, for equilibrium I, and state its units.
Kstab =
units ................................................
[2]
Cadmium ions are poisonous and need to be removed from some water supplies. This is often
done by adding a complexing agent.
(ii)In a sample of ground water the concentration of Cd2+(aq) is 1.00 × 10–4 mol dm–3.
Calculate the concentration of CH3NH2(aq) needed to reduce the concentration of Cd2+(aq)
in this dilute solution by a factor of one thousand.
concentration of CH3NH2(aq) = ............................. mol dm–3 [2]
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(b)Values for ∆H o and ∆G o for equilibria I and II, and the value of ∆S o for equilibrium I, are given
in the table below. All values are at a temperature of 298 K.
equilibrium
∆H o / kJ mol–1
∆G o / kJ mol–1
∆S o / J K–1 mol–1
I
–57.3
–37.4
–66.8
II
–56.5
–60.7
to be calculated
(i)Suggest a reason why the ∆H o values for the two equilibria are very similar.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)Calculate ∆S o for equilibrium II.
∆S o = ............................. J K–1 mol–1 [1]
(iii)Suggest a reason for the difference between the ∆S o you have calculated for equilibrium II
and that for equilibrium I given in the table.
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(iv)Which of the two complexes is the more stable? Give a reason for your answer.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
[Total: 8]
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6Esterases are enzymes that hydrolyse esters.
O
R
O
C
+ H2O
O
R
R'
+ HO–R'
C
O
H
Enzymes can be quite specific in the structures of the substrates they act upon. For example, an
esterase isolated from the mould Aspergillus niger will hydrolyse phenyl ethanoate, CH3CO2C6H5,
but not its isomer methyl benzoate, C6H5CO2CH3.
(a)Outline how enzymes catalyse reactions, and explain their specificity.
Use diagrams in your answer where appropriate.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
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(b)Sample bottles of each of the isomers phenyl ethanoate and methyl benzoate have lost their
labels and so have been named isomer A and isomer B.
(i)The carbon-13 NMR spectra of isomers A and B contain the following peaks.
isomer A
isomer B
δ 52
δ 26
δ 128
δ 122
δ 129
δ 126
δ 130
δ 129
δ 133
δ 151
δ 167
δ 169
The identity of the compound responsible for each spectrum can be deduced by studying
the chemical shifts (δ) of the peaks in the spectra.
Use the Data Booklet to assign the correct peaks to the labelled carbon atoms in the
structures of the isomers below. Write each value next to the relevant carbon atom and
hence deduce the identity of each isomer.
...................
O
C
O
CH3
C
...................
phenyl ethanoate is isomer ...............
...................
O
O
CH3
...................
methyl benzoate is isomer ...............
[2]
(ii)These two isomers are difficult to distinguish chemically.
Describe a method of converting them to suitable products in step 1 which can then be
tested in step 2.
You should state the reagents and conditions for each step, and any observations you
would make.
step 1 . .................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
step 2 . .................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
[3]
[Total: 8]
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7
(a)Amino acids can be separated by electrophoresis.
(i)Draw a labelled diagram of the apparatus used to separate a mixture by electrophoresis.
[3]
(ii)Explain the principles of the separation of amino acids by electrophoresis.
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [2]
(b)Electrophoresis is usually carried out in a buffer solution.
Given three buffers, with pH values of 2.0, 7.0 and 12.0, suggest, with a reason, which buffer
would be the most suitable for the separation of the following amino acid mixtures.
Your reasons should refer to the structure of each molecule.
(The structures of these amino acids are given in the Data Booklet.)
(i)Asp and Val
buffer pH ..............................................................................................................................
reason . ................................................................................................................................
. ............................................................................................................................................
(ii)Lys and Ser
buffer pH ..............................................................................................................................
reason . ................................................................................................................................
. ............................................................................................................................................
(iii)Tyr and Phe
buffer pH ..............................................................................................................................
reason . ................................................................................................................................
. ............................................................................................................................................
[3]
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(c) (i)Draw the structure of the dipeptide Gly-Ser, showing the peptide bond in full.
[2]
The infra-red spectrum of Gly-Ser is shown below.
transmittance
100
50
E
0
4000
G
F
3000
2000
1500
wavenumber / cm
1000
500
–1
(ii)Use the Data Booklet to identify the bond in the molecule of Gly-Ser that is responsible for
each of the peaks indicated on the above infra-red spectrum.
E ............................................
F ............................................
G ............................................
[2]
[Total: 12]
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8
(a)Describe and explain the trend in the solubility of the hydroxides down Group 2.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
(b)Calcium reacts vigorously with HCl (aq) producing H2(g).
Ca(s) + 2HCl (aq) → CaCl 2(aq) + H2(g)
(i)How would you expect the enthalpy change for this reaction to compare with the enthalpy
change for the reaction where HNO3(aq) is used in place of HCl but all other conditions
are the same?
Explain your answer.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
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17
(ii)The ionic equation for this reaction is shown.
Ca(s) + 2H+(aq) → Ca2+(aq) + H2(g)
∆H o = x kJ mol–1
Construct a fully labelled Hess’ Law cycle to connect each side of this equation to the
relevant gas phase ions.
Use your cycle, the following data, and data from the Data Booklet, to calculate a value for x.
standard enthalpy of atomisation of Ca(s),
(Ca)
standard enthalpy of hydration of Ca2+(g),
(Ca2+)
standard enthalpy of hydration of H+(g),
(H+)
+178 kJ mol–1
–1576 kJ mol–1
–1090 kJ mol–1
x = ............................ kJ mol–1 [4]
(c)The standard enthalpy change for the reaction between Ca(s) and CH3CO2H(aq) is less
negative than x by 2 kJ mol–1.
Suggest an explanation for this.
....................................................................................................................................................
.............................................................................................................................................. [2]
[Total: 10]
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9The anti-inflammatory drug ibuprofen can be synthesised from benzene via the following six steps.
step 1
step 2
H
OH
step 3
CN
step 4
CO2H
step 5
CO2H
step 6
J
ibuprofen
(a)Draw circles around any chiral carbon atoms in the above five formulae.
[1]
(b)Suggest the structures of compounds H and J and draw them in the boxes above.
[2]
(c)Suggest reagents and conditions for steps 1-6.
step 1 . ........................................................................................................................................
step 2 . ........................................................................................................................................
step 3 . ........................................................................................................................................
step 4 . ........................................................................................................................................
step 5 . ........................................................................................................................................
step 6 . ........................................................................................................................................
[6]
(d)Name the mechanism of step 1 and state the type of reaction for step 6.
step 1 . ........................................................................................................................................
step 6 . ........................................................................................................................................
[2]
[Total: 11]
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10 (a) (i)Complete the electronic configuration of the iron atom.
Fe
1s22s22p6...................................
[1]
(ii)In some of its complexes, the Fe3+ ion has only one unpaired electron in its d orbitals.
Using the symbols ↑ and ↓ to represent electrons of opposite spins, complete the following
diagram to show the d orbital electronic configuration of this Fe3+ ion.
3d
........
........
........
........
energy
........
[1]
(b)A solution containing a mixture of Sn2+(aq) and Sn4+(aq) is added to a solution containing a
mixture of Fe2+(aq) and Fe3+(aq).
Use E o data from the Data Booklet to predict the reaction that might take place when the two
solutions are mixed, and write an equation for the reaction.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
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(c)Hexaaquairon(III) ions are pale violet. They form a colourless complex with fluoride ions, F–,
equilibrium 1, and a deep-red complex with thiocyanate ions, SCN–, equilibrium 2.
[Fe(H2O)6]3+ + F–
violet
[Fe(H2O)6]3+ + SCN–
violet
[Fe(H2O)5F]2+ + H2O
colourless
[Fe(H2O)5SCN]2+ + H2O
deep-red
equilibrium 1 Kstab = 2.0 × 105 mol–1 dm3
equilibrium 2 Kstab = 1.0 × 103 mol–1 dm3
(i)Predict and explain the sequence of colour changes you would observe in each of the
following experiments.
•A few drops of KSCN(aq) are added to 5 cm3 of Fe3+(aq), followed by a few drops of
KF(aq).
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
•A few drops of KF(aq) are added to 5 cm3 of Fe3+(aq), followed by a few drops of
KSCN(aq).
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
[4]
(ii)What type of reaction is occurring during the experiments in (i)?
. ...................................................................................................................................... [1]
[Total: 9]
Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable
effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will
be pleased to make amends at the earliest possible opportunity.
To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International
Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after
the live examination series.
Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local
Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.
© UCLES 2016
9701/42/M/J/16
2
Answer all the questions in the spaces provided.
1Copper is a transition element and has atomic number 29.
(a)Complete the electronic configuration for the copper atom and the copper ion in the +2 oxidation
state.
•
copper atom
[Ar] ...............................................................
•
copper ion in the +2 oxidation state
[Ar] ...............................................................
[2]
(b)The following equilibrium exists between two complex ions of copper in the +2 oxidation state.
[Cu(H2O)6]2+ + 4Cl –
[CuCl 4]2– + 6H2O
(i)Name the type of reaction occurring here.
. ...................................................................................................................................... [1]
(ii)State the colours of these two complex ions.
[Cu(H2O)6]2+ ................................................. [CuCl 4]2– ................................................. [1]
(iii)State the shape of the [CuCl 4]2– ion.
. ...................................................................................................................................... [1]
(iv)Write the expression for the stability constant, Kstab, for this equilibrium.
Kstab =
[1]
(c)Copper also forms the complex ions [Cu(NH3)2(H2O)4]2+ and [Cu(en)(H2O)4]2+ where en is the
bidentate ligand ethane-1,2-diamine, H2NCH2CH2NH2.
[Cu(H2O)6]2+ + 2NH3
[Cu(H2O)6]2+ + en
[Cu(NH3)2(H2O)4]2+ + 2H2O
equilibrium 1
[Cu(en)(H2O)4]2+ + 2H2O
equilibrium 2
(i)What is meant by the term bidentate ligand?
. ............................................................................................................................................
. ...................................................................................................................................... [2]
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(ii)The table lists the values of stability constants for these two complexes.
stability constant, Kstab
[Cu(NH3)2(H2O)4]2+
7.94 × 107
[Cu(en)(H2O)4]2+
3.98 × 1010
What do these Kstab values tell us about the relative positions of equilibria 1 and 2?
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(d)Nickel forms the complex ion [Ni(en)3]2+ in which it is surrounded octahedrally by six nitrogen
atoms.
(i)Name the type of stereoisomerism displayed by [Ni(en)3]2+.
. ...................................................................................................................................... [1]
(ii)Draw three-dimensional diagrams to show the two stereoisomers of [Ni(en)3]2+.
[3]
(e)Ethane-1,2-diamine is a useful reagent in organic chemistry.
(i)Explain how the amino groups in ethane-1,2-diamine allow the molecule to act as a
Brønsted-Lowry base.
. ............................................................................................................................................
. ...................................................................................................................................... [2]
(ii)Write an equation for the reaction of ethane-1,2-diamine with an excess of
hydrochloric acid.
. ...................................................................................................................................... [1]
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(f)
(i)Under certain conditions, ethane-1,2-diamine reacts with ethanedioic acid, HO2CCO2H, to
form the polymer Z.
Draw the structure of this polymer, Z, showing two repeat units.
[2]
(ii)Name the type of reaction occurring during this polymerisation.
. ...................................................................................................................................... [1]
(iii)Polymer Z is an example of a biodegradable polymer.
Name a polymer that is non-biodegradable.
. ...................................................................................................................................... [1]
[Total: 20]
© UCLES 2016
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2
(a)When copper(II) carbonate is heated strongly, it decomposes in a similar way to Group 2
carbonates.
Predict what would be observed when anhydrous copper(II) carbonate is heated.
....................................................................................................................................................
.............................................................................................................................................. [1]
(b)Describe and explain how the thermal stability of the Group 2 carbonates varies down the
group.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
(c)Calcium cyanamide, CaCN2, can be used as a fertiliser.
(i)Complete the ‘dot-and-cross’ diagram for the cyanamide ion, CN22–.
Use the following key for the electrons.
•
×
□
electrons from carbon
electrons from nitrogen
added electron(s) responsible for the overall negative charge
2–
N
C
N
[2]
(ii)CaCN2 decomposes readily on contact with water forming an insoluble white solid and
ammonia only.
Suggest an equation for this reaction.
. ...................................................................................................................................... [2]
[Total: 8]
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3The spontaneity (feasibility) of a chemical reaction depends on the standard Gibbs free energy
change, ∆G o. This is related to the standard enthalpy and entropy changes by the equation shown.
∆G o = ∆H o – T∆S o
(a)State and explain whether the following processes will lead to an increase or decrease in
entropy.
(i)the reaction of magnesium with hydrochloric acid
entropy change . ..................................................................................................................
explanation ..........................................................................................................................
[1]
(ii)solid potassium chloride dissolving in water
entropy change . ..................................................................................................................
explanation ..........................................................................................................................
[1]
(iii)steam condensing to water
entropy change . ..................................................................................................................
explanation ..........................................................................................................................
[1]
(b)Magnesium carbonate can be decomposed.
MgCO3(s) → MgO(s) + CO2(g)
∆H o = +117 kJ mol–1
Standard entropies are shown in the table.
substance
MgCO3(s)
MgO(s)
CO2(g)
S o / J mol–1 K–1
+65.7
+26.9
+214
(i)Calculate ∆G o for this reaction at 298 K.
Include a relevant sign and give your answer to three significant figures.
∆G o = ............................. kJ mol–1 [3]
(ii)Explain, with reference to ∆G o, why this reaction becomes more feasible at higher
temperatures.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
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(c)On heating, sodium hydrogencarbonate decomposes into sodium carbonate as shown.
2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g)
∆H o = +130 kJ mol–1
∆S o = +316 J mol–1 K–1
Calculate the minimum temperature at which this reaction becomes spontaneous (feasible).
Show your working.
temperature = ............................. K [2]
(d)The solubility of Group 2 sulfates decreases down the Group.
Explain this trend.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
[Total: 11]
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4
(a)Cobalt is a transition element that forms complex ions with oxidation states +2 and +3.
Explain what is meant by the term transition element.
....................................................................................................................................................
.............................................................................................................................................. [1]
(b)The following scheme shows some reactions of [Co(H2O)6]2+.
[Co(H2O)6]2+
OH–(aq)
precipitate A
excess
Cl –(aq)
solution of B
excess
NH3(aq)
solution of C
(i)State the formula of each of the following.
A ......................................................
B ......................................................
C ......................................................
(ii)State the colour of the following solutions.
[2]
[Co(H2O)6]2+ .................................................
solution of B . ...............................................
solution of C . ...............................................
[2]
(c)Define the term standard electrode potential.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
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(d)An electrochemical cell was set up to measure the standard electrode potential,
made of a Co2+ / Co half-cell and a Fe3+ / Fe2+ half-cell.
, of a cell
(i)Complete the table with the substance used to make the electrode in each of these
half-cells.
half-cell
electrode
Co2+ / Co
Fe3+ / Fe2+
[1]
(ii)Write the equation for the overall cell reaction.
. ...................................................................................................................................... [1]
(iii)Use the Data Booklet to calculate the
.
= ............................. V [1]
(e)The electrochemical cell in (d) was set up again but this time the concentration of Co2+(aq) was
0.050 mol dm–3.
The Nernst equation can be used to calculate the value of an electrode potential at different
concentrations.
E = E o + (0.059 / z) log [Co2+(aq)]
Nernst equation
(i)Use the Data Booklet and the Nernst equation to calculate the value of E for the
Co2+ / Co half-cell in this experiment.
E for Co2+ / Co = ............................. V [1]
(ii)Suggest how this change will affect the overall cell potential, Ecell, compared to
(d)(iii).
Circle your answer.
less positive
no change
more positive
in
[1]
(f)Iron(III) ions can oxidise vanadium metal.
Construct an equation for the reaction of an excess of iron(III) ions with vanadium metal.
Use of the Data Booklet will be helpful.
.............................................................................................................................................. [2]
[Total: 14]
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5Compound F contains the elements carbon, hydrogen and oxygen only. All carbon-carbon bonds
in F are single bonds. The structure of F was analysed by mass spectrometry and infra-red and
NMR spectroscopy.
(a)The mass spectrum shows that the m / e value for the M peak is 90.
The ratio of the heights of the M and M+1 peaks is 22.1 : 0.7.
(i)Use the ratio of the heights of the M and M+1 peaks to calculate the number of carbon
atoms in a molecule of F.
number of carbon atoms = ............................. [2]
(ii)Suggest the molecular formula of F.
molecular formula =
C H O
[1]
(b)The infra-red spectrum of F was obtained.
Use the Data Booklet and your knowledge of infra-red spectroscopy to identify the type of bond
and the functional group responsible for these three absorptions.
absorption / cm–1
appearance of the peak
3350
broad and strong
2680
very broad and strong
1725
strong
type of bond
functional group
[2]
© UCLES 2016
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(c)F was dissolved in deuterated trichloromethane, CDCl 3, and the proton NMR spectrum of this
solution obtained.
14
13
12
11
10
9
8
7
6
δ / ppm
5
4
3
2
1
0
(i)Use the Data Booklet and your answer to (a)(ii) to complete Table 1 for the proton NMR
spectrum of F.
The actual chemical shifts for the four absorptions in F have been added for you.
Table 1
δ / ppm
type of proton
relative peak area
1.4
3.9
4.7
12.9
[4]
(ii)Describe and explain the splitting pattern for the absorption at δ = 1.4.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(iii)F was dissolved in D2O and the proton NMR spectrum of this new solution obtained.
Two of the absorptions in Table 1 were not present in this spectrum.
Which absorptions were not present?
......................................... and .........................................
[1]
(iv)Suggest the structure of F.
[1]
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(d)Molecules of cycloheptadiene, C7H10, consist of a seven-membered ring with two
carbon-carbon double bonds.
(i)Complete the skeletal formulae of two isomers of cycloheptadiene.
P
Q
[1]
The isomers P and Q were analysed using carbon-13 NMR spectroscopy.
(ii)Predict the number of peaks that will be seen in the carbon-13 NMR spectra of P and Q.
isomer
number of peaks
P
Q
[2]
[Total: 15]
© UCLES 2016
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6Ibuprofen and paracetamol are pain-relief drugs.
O
OH
O
OH
N
H
ibuprofen
paracetamol
(a)Ibuprofen and paracetamol both contain the aryl (benzene) functional group.
Name the other functional groups present in each molecule.
ibuprofen ....................................................................................................................................
paracetamol . ..............................................................................................................................
[2]
(b)Ibuprofen contains a chiral centre and shows stereoisomerism.
(i)State what is meant by the term chiral centre.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
(ii)Draw the two stereoisomers of ibuprofen.
C
C
[2]
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(c)Draw the structures of the organic products when ibuprofen and paracetamol react separately
with LiAl H4.
product with ibuprofen
product with paracetamol
[2]
(d)A student carried out some reactions with solutions of ibuprofen and paracetamol using
reagents D and E and the following results were obtained.
( means a reaction took place.)
reagent
ibuprofen
paracetamol
D


E


(i)Suggest a possible identity for each reagent D and E.
D .............................................
E .............................................
[2]
(ii)Give the structure of the organic product formed when reagent D reacted with ibuprofen.
product with ibuprofen
[1]
(iii)Give the structure of the organic product formed when reagent E reacted with paracetamol.
product with paracetamol
© UCLES 2016
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[1]
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16
(e)One of the steps in the manufacture of ibuprofen is shown.
CH3COCl
Al Cl 3
X
O
Y
(i)Write an equation for the reaction between CH3COCl and Al Cl 3.
. ...................................................................................................................................... [1]
(ii)Complete the mechanism for the conversion of X into Y. Include all necessary curly arrows,
any relevant dipoles and charges.
X
[3]
(iii)Name the mechanism in (ii).
. ...................................................................................................................................... [1]
[Total: 16]
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7
(a)Sodium chlorate(I), NaCl O, is the active ingredient in commercial bleach. The concentration
of chlorate(I) ions was determined by titration.
•10.0 cm3 of a bleach solution was diluted to 250 cm3 in a volumetric flask using distilled
water.
•Dilute sulfuric acid and an excess of potassium iodide solution were added to a
25.0 cm3 portion of this solution to liberate iodine.
•The resulting solution required 20.80 cm3 of 0.100 mol dm–3 aqueous sodium thiosulfate
solution to react with the iodine produced.
The titration reactions are shown.
Cl O– + 2I– + 2H+ → I2 + Cl – + H2O
I2 + 2S2O32– → 2I– + S4O62–
Calculate the concentration, in mol dm–3, of Cl O– ions in the bleach solution.
concentration of Cl O– = ............................. mol dm–3 [3]
(b)An indicator was used in the thiosulfate-iodine titration.
(i)Name a suitable indicator for this titration.
. ...................................................................................................................................... [1]
(ii)State the expected colour change you would observe at the end-point in this titration.
from ............................................................ to ............................................................ [1]
(iii)State when in the procedure you would add the indicator.
. ............................................................................................................................................
. ...................................................................................................................................... [1]
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(c)The concentration of chlorate(I) ions can also be determined by adding an excess of
hydrogen peroxide to the sample of bleach and measuring the volume of oxygen gas produced.
H2O2 + NaCl O → NaCl + O2 + H2O
hydrogen peroxide
oxygen gas
100 cm3 measuring
cylinder
water
5.0 cm3 bleach
When an excess of aqueous hydrogen peroxide was added to 5.0 cm3 of a different bleach
solution, 82 cm3 of oxygen was produced at room temperature and pressure.
Calculate the concentration of Cl O– ions in this bleach solution.
concentration of Cl O– = ............................. mol dm–3 [2]
(d)Trichlorocyanuric acid, C3Cl 3N3O3, acts as a chlorine buffer and disinfectant for swimming
pools. It reacts with water to give chloric(I) acid, HCl O.
C3Cl 3N3O3 + 3H2O
C3H3N3O3 + 3HCl O
(i)Write the expression for Kc for this equilibrium.
Kc =
[1]
(ii)In outdoor swimming pools, the HCl O is decomposed by sunlight. The decomposition of
HCl O is a redox reaction which forms a gas that relights a glowing splint.
Describe and explain the effect of the decomposition of HCl O on the equilibrium in (d).
State the effect on Kc.
. ............................................................................................................................................
. ............................................................................................................................................
effect on Kc ..........................................................................................................................
[2]
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(iii)The decomposition of HCl O is a redox reaction.
Suggest an equation for this reaction.
. ...................................................................................................................................... [1]
(e)The buffer solution in blood is a mixture of carbonic acid, H2CO3, and hydrogencarbonate ions,
HCO3–. Healthy blood has a pH of 7.40.
H2CO3 + H2O
HCO3– + H3O+
Ka = 7.94 × 10–7 mol dm–3
(i)Explain how this buffer system acts to control the blood pH. Include equations in your
answer.
. ............................................................................................................................................
. ............................................................................................................................................
. ............................................................................................................................................
. ...................................................................................................................................... [2]
(ii)A patient’s blood has a [HCO3–] : [H2CO3] ratio of 9.5 : 1.
Calculate the pH of the patient’s blood.
pH = ............................ [2]
[Total: 16]
Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable
effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will
be pleased to make amends at the earliest possible opportunity.
To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International
Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after
the live examination series.
Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local
Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.
© UCLES 2016
9701/41/O/N/16
2
Answer all the questions in the spaces provided.
1
Transition elements are important metals because of their characteristic properties.
(a) Define what is meant by a transition element.
....................................................................................................................................................
.............................................................................................................................................. [1]
(b) (i) For each of the following complexes, state the co-ordination number and the oxidation
number of the transition element present.
co-ordination number
oxidation number
[Ni(CN)2(NH3)2]
[CrCl 2(H2O)4]+
[2]
(ii)
State the type of bonding that exists between the ligand and the metal ion in these
complexes.
....................................................................................................................................... [1]
(iii)
Suggest the structure of [Ni(CN)2(NH3)2] and name its shape.
name of shape ....................................................................................................................
[2]
(c) The complex ion [Cr(H2O)6]3+ can be converted into [CrCl 2(H2O)4]+.
(i)
Suggest a suitable reagent for this conversion.
....................................................................................................................................... [1]
(ii)
State the type of reaction in (i).
....................................................................................................................................... [1]
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(d) The [CrCl 2(H2O)4]+ complex ion shows stereoisomerism.
(i)
Name this type of stereoisomerism.
....................................................................................................................................... [1]
(ii)
Draw three-dimensional diagrams to show the two stereoisomers of [CrCl 2(H2O)4]+.
[3]
[Total: 12]
© UCLES 2016
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2
Most car air bags contain a capsule of sodium azide, NaN3. In a crash, the NaN3 decomposes into
its elements.
(a) Write an equation for the decomposition of NaN3.
.............................................................................................................................................. [1]
(b) Complete the ‘dot-and-cross’ diagram for the azide ion, N3–.
Use the following key for the electrons.


□
electrons from central nitrogen atom
electrons from the other two nitrogen atoms
added electron(s) responsible for the overall negative charge
–
N
N
N
[3]
(c) Lattice energies are always negative showing that they represent exothermic changes.
(i)
Explain what is meant by the term lattice energy.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(ii)
Explain why lattice energy represents an exothermic change.
.............................................................................................................................................
....................................................................................................................................... [1]
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(iii)
Use the following data and any relevant data from the Data Booklet to calculate the
standard enthalpy change of formation,
, of NaN3(s).
Include a sign in your answer. Show all your working.
lattice energy,
–732 kJ mol–1
, of NaN3(s)
standard enthalpy change of atomisation,
, of Na(g)
standard enthalpy change, H o, for 1 12 N2(g) + e–  N3–(g)
+107 kJ mol–1
+142 kJ mol–1
of NaN3(s) = ............................. kJ mol–1 [3]
(iv)
The lattice energy,
, of RbN3(s) is – 636 kJ mol–1.
Suggest why the lattice energy of NaN3(s), –732 kJ mol–1, is more exothermic than that of
RbN3(s).
.............................................................................................................................................
....................................................................................................................................... [1]
[Total: 11]
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3
Iron has atomic number 26.
(a) Complete the electronic configuration for the iron atom and the iron ion in the +3 oxidation
state.

iron atom
[Ar] ................................................

iron ion in the +3 oxidation state
[Ar] ................................................
[2]
(b) Fe3+ can act as a homogeneous catalyst in the reaction between peroxodisulfate ions (S2O82–)
and iodide ions.
(i)
What is meant by a homogeneous catalyst?
.............................................................................................................................................
....................................................................................................................................... [1]
(ii)
Write an equation for the overall reaction between S2O82–(aq) and I–(aq).
....................................................................................................................................... [1]
(iii)
Suggest why, in the absence of a catalyst, the activation energy for this reaction is high.
.............................................................................................................................................
....................................................................................................................................... [1]
(iv)
Write two equations to show how Fe3+(aq) ions can catalyse the reaction between
S2O82–(aq) ions and I–(aq) ions.
equation 1 ...........................................................................................................................
equation 2 ...........................................................................................................................
[2]
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(c) Iron(III) oxide can be reduced to iron metal using carbon monoxide at a temperature of 1000 C.
Fe2O3(s) + 3CO(g)  2Fe(s) + 3CO2(g)
H o = – 43.6 kJ mol–1
Some relevant standard entropies are given in the table.
(i)
substance
Fe2O3(s)
CO(g)
Fe(s)
CO2(g)
S o / J K–1 mol–1
+90
+198
+27
+214
What is meant by the term entropy ?
.............................................................................................................................................
....................................................................................................................................... [1]
(ii)
Calculate the standard entropy change, S o, for this reaction.
S o = ............................. J K–1 mol–1 [2]
(iii)
Calculate the standard Gibbs free energy change, G o, for this reaction at 25 C.
G o = ............................. kJ mol–1 [2]
(iv)
Suggest why a temperature of 1000 C is usually used for this reaction, even though the
reaction is spontaneous (feasible) at 25 C. Explain your answer.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [1]
[Total: 13]
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8
4
(a) Explain why compounds of transition elements are usually coloured.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [3]
(b) Copper is used to make alloys such as brass. The percentage of copper in a sample of brass
can be determined by dissolving the sample in concentrated nitric acid and reacting the mixture
with potassium iodide. The resulting solution is then titrated.
A 1.75 g sample of the brass was dissolved in excess concentrated nitric acid.
The reaction of the copper metal in the brass with the concentrated nitric acid released a brown
gas and formed a green-blue solution.
(i)
Write an equation for this reaction.
....................................................................................................................................... [2]
The resulting solution was neutralised and made up to 250 cm3 in a volumetric flask with distilled
water.
An excess of aqueous potassium iodide was added to a 25.0 cm3 portion of this solution to
liberate iodine.
The resulting solution required 22.40 cm3 of 0.100 mol dm–3 aqueous sodium thiosulfate solution
to react with the iodine produced.
The reactions taking place in this titration are shown.
2Cu2+ + 4I–  2CuI + I2
I2 + 2S2O32–  2I– + S4O62–
(ii)
Calculate the percentage of copper, by mass, in the sample of brass to three significant
figures.
% of copper = ............................. [4]
[Total: 9]
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5
The phosphate buffer system operates in biological cells. The buffer contains dihydrogen phosphate,
H2PO4–, which acts as a weak acid.
H2PO4– + H2O
HPO42– + H3O+
(a) Write an expression for the Ka of H2PO4–.
Ka =
[1]
(b) (i) Explain what is meant by the term buffer solution.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(ii)
Write two equations to show how a solution containing a mixture of H2PO4– and HPO42–
acts as a buffer.
.............................................................................................................................................
....................................................................................................................................... [2]
(c) The pH in many living cells is 7.40.
H2PO4– + H2O
HPO42– + H3O+
Ka = 6.31  10–8 mol dm–3
Calculate the value of [HPO42–] / [H2PO4–] needed to give a pH of 7.40 in the cells.
[HPO42–] / [H2PO4–] = ............................. [3]
(d) (i) The H2PO4– ion can also act as a base.
Write an equation to show H2PO4– acting as a base.
....................................................................................................................................... [1]
(ii)
The HPO42– ion can also act as an acid.
Write an equation to show HPO42– acting as an acid.
....................................................................................................................................... [1]
[Total: 10]
© UCLES 2016
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10
6
Oleocanthal, Q, is a natural compound found in olive oil. It has antioxidant and anti-inflammatory
properties and is thought to have a protective effect against Alzheimer’s disease.
O
O
O
HO
Q
O
(a) Q shows optical and cis-trans isomerism.
On the structure of Q above, circle the functional group that shows cis-trans isomerism and
indicate with an asterisk (*) the chiral carbon atom.
[1]
(b) Q can be isolated from olive oil by partitioning between two solvents.
(i)
Explain what is meant by the term partition coefficient.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(ii)
When 40.0 cm3 of hexane was shaken with 10.0 cm3 of a solution containing 0.25 g of Q in
10.0 cm3 of methanol, it was found that 0.060 g of Q was extracted into the hexane.
Calculate the partition coefficient, Kpartition, of Q between hexane and methanol.
Kpartition = ............................. [2]
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(c) Complete the following table to show the structures of the products formed when Q reacts with
the three reagents.
reagent
structure of product(s)
type of reaction
excess
Br2(aq)
NaBH4
excess hot
NaOH(aq)
[6]
(d) When a sample of Q synthesised in a laboratory was compared to a natural sample from olive
oil, it was found that the therapeutic activity of the synthetic sample was lower.
Suggest a reason for this.
....................................................................................................................................................
.............................................................................................................................................. [1]
[Total: 12]
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13
7
(a) Bromobenzene can be prepared from benzene as shown.
Br2
Al Br3
(i)
Br
Name the mechanism of this reaction.
....................................................................................................................................... [1]
(ii)
Draw the mechanism of this reaction. Include all relevant curly arrows, any dipoles and
charges.
[4]
(b) Two isomeric aromatic compounds, V and W, each contain three functional groups, two of
which are shown in the table.
O
Br
Br
NH
NH
V
O
CH3
CH3
W
Complete the table with the other functional groups present in V and W.
substance
functional groups present
V
bromo group
aryl (benzene) group
............................
W
bromo group
aryl (benzene) group
............................
[1]
© UCLES 2016
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14
(c) Compounds V and W can be synthesised from bromobenzene by the following routes.
Br
CH3
step 2
PCl 5
R
S
step 1
CH3NH2
O
Br
Br
NH
Br
CH3
V
step 3
NO2
step 4
CH3COCl
Br
NH
T
W
(i)
O
CH3
Suggest reagents for each of the steps 1– 4.
step 1 ..................................................................................................................................
step 2 ..................................................................................................................................
step 3 ..................................................................................................................................
step 4 ..................................................................................................................................
[4]
(ii)
Deduce structures for R, S and T and draw their structural formulae in the boxes.
[3]
(d) (i) Draw the structures of the two organic products from the reaction of V and W with LiAl H4.
product from V
product from W
[2]
© UCLES 2016
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(ii)
Name the type of reaction occurring between LiAl H4 and V or W.
....................................................................................................................................... [1]
(e) V and W can be hydrolysed using hot HCl (aq).
(i)
Draw the structures of the two organic products of the hydrolysis of W.
Br
NH
O
HCl (aq)
+
heat
CH3
W
[2]
(ii)
The products formed from the hydrolysis of W are soluble in aqueous acid, whereas a
precipitate, X, is formed on hydrolysing V.
Draw the structure of compound X.
X
[1]
(iii)
Suggest why X is insoluble in water.
.............................................................................................................................................
....................................................................................................................................... [1]
[Total: 20]
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16
8
Compound F is a carboxylic acid.
(a) Compound F contains 31.4% oxygen by mass and its mass spectrum has a molecular ion
peak at m / e = 102.
Use all of this information to show that the molecular formula of compound F is C5H10O2.
Show all your working.
[1]
(b) There are four possible structural isomers of C5H10O2 that are carboxylic acids.
(i)
The first isomer has been drawn.
Draw the skeletal formulae of the three other structural isomers.
O
OH
isomer 1
isomer 2
isomer 3
isomer 4
[2]
(ii)
State the systematic name of isomer 1.
....................................................................................................................................... [1]
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(c) F is one of the four structural isomers in (b)(i). A carbon-13 NMR spectrum of F is shown.
180
(i)
160
140
120
100
80
δ / ppm
60
40
20
0
Use the spectrum to identify isomer F. Draw its structure in the box below.
F
[1]
(ii)
Use the Data Booklet and your knowledge of carbon-13 NMR spectroscopy to identify the
environments and hybridisations of the carbon atoms responsible for each of the three
absorptions.
 / ppm
environment of
the carbon atom
hybridisation of
the carbon atom
27
41
179
[2]
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18
(d) G is another of the four structural isomers in (b)(i). The proton NMR spectrum of G is shown.
12
(i)
11
10
9
8
7
6
5
δ / ppm
4
3
2
1
0
Use the Data Booklet and the spectrum to complete the table below.
The actual chemical shifts for the four absorptions in G and the splitting pattern at
 = 1.6 ppm have been added for you.
 / ppm
type of proton
number of protons
splitting pattern
0.9
1.6
multiplet
2.4
11.5
[4]
(ii)
Deduce which isomer is G and draw its structure in the box.
G
[1]
© UCLES 2016
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(e) Name or give the formula of a suitable solvent for obtaining a proton NMR spectrum.
.............................................................................................................................................. [1]
[Total: 13]
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