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Raffles Institution 2013 9647/Y6/T3/13 [Turn Over
RAFFLES INSTITUTION 2013 YEAR 6 TERM 3 COMMON TEST Higher 2
CHEMISTRY 9647
4 July 2013
2 hours 30 minutes
Additional Materials: OMR Answer Sheet Writing Papers Data
Booklet
READ THESE INSTRUCTIONS FIRST DO NOT open this booklet until you
are told to do so. Write your name and civics tutorial group in the
spaces provided on the cover sheets on pages 11 and 27. This paper
consists of three sections A, B and C. Section A (20 marks)
consists of 20 multiple-choice questions. Record your answers to
this section in soft pencil on the separate OMR Answer Sheet.
Section B (35 marks) consists of 4 structured questions. Answers to
this section are to be written in the spaces provided in the
question paper. Section C (40 marks) consists of 2 free-response
questions. Answers to this section are to be written on the writing
papers provided. You are to begin each question on a fresh page of
paper. You are reminded of the need for good English and clear
presentation in your answers. The number of marks is given in
brackets [ ] at the end of each question or part question. Write in
dark blue or black pen. You may be subject to penalty for writing
answers in pencil.
This document consists of 27 printed pages.
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Section A (20 marks)
For each question, there are four possible answers, A, B, C and
D. Choose the one you consider to be correct and record your choice
on the OMR Answer Sheet provided. 1 The values of some
thermochemical data for barium chloride are given in the table
below.
Lattice energy of barium chloride = 2065 kJ mol1
Standard enthalpy change of hydration of barium ions = 2494 kJ
mol1
Standard enthalpy change of hydration of chloride ions = 363 kJ
mol1
What is the standard enthalpy change of solution of barium
chloride?
A 5285 kJ mol1 B 4922 kJ mol1
C 1155 kJ mol1 D 792 kJ mol1
2 The enthalpy change of neutralisation between aqueous sodium
hydroxide and
hydrochloric acid is 57.2 kJ mol1, but the enthalpy change of
neutralisation
between aqueous sodium hydroxide and ethanoic acid is 55.2 kJ
mol1.
Which statement best explains the numerical difference between
these values?
A The ionisation of ethanoic acid to give hydrogen ions in water
is an
endothermic process.
B Aqueous ethanoic acid contains fewer hydrogen ions than
hydrochloric acid of
the same concentration.
C The reaction between aqueous sodium hydroxide and aqueous
ethanoic acid
produces less than 1 mole of water.
D A smaller volume of aqueous ethanoic acid than that of aqueous
hydrochloric
acid of the same concentration is required for the
neutralisation.
3 Which statement about the equilibrium shown below is
correct?
[Fe(H2O)6]3+(aq) + H2O(l) [Fe(H2O)5OH]
2+(aq) + H3O+(aq) H > 0
lilac orange A The equilibrium constant has no units.
B The solution turns lilac when pH is increased.
C The equilibrium constant increases when the mixture is
diluted.
D The rate constant of the backward reaction increases with
temperature.
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4 A gaseous reactant, R was injected into a vessel and allowed
to reach equilibrium
with its gaseous product, P. The production of P is
endothermic.
The following graph shows the change in concentrations of R and
P with time.
Which of the following changes occurred at t2?
A More R was added.
B The temperature was increased.
C An inert gas was added at constant pressure.
D The volume of the vessel was reduced at constant
temperature.
5 A pure sample of NH3(g) is introduced into an evacuated vessel
of constant volume.
This vessel is maintained at constant temperature such that the
equilibrium below is
established.
2NH3(g) N2(g) + 3H2(g)
The value of the final pressure is then found to be 40% greater
than if only NH3 were
present. What is the mole fraction of H2 in the reaction
mixture?
A 0.14 B 0.28 C 0.43 D 0.71
6 A 25.0 cm3 sample of 0.35 mol dm3 HCOOH is titrated with 0.20
mol dm3 KOH.
What is the pH of the solution after an equal volume of KOH has
been added to the
acid? Given: Ka (HCOOH) = 1.77 104 mol dm3.
A 3.75.1/0.075 B 3.88pH C 8.50pH D 11.74pH
time / min
concentration
t1 t2 t3
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7 A diprotic acid H2A has Ka1 = 1 104 mol dm3 and Ka2 = 1 10
8 mol dm3. The
corresponding base A2 is titrated with aqueous HCl, both
solutions being
0.1 mol dm3. Which of the following diagrams best represents the
titration curve?
A
B
C
D
8 Reaction Observation
Metal X is placed in a solution of metal ions Y2+.
X dissolves and Y2+ is displaced from the solution as Y.
Metal Y is placed in acid solution. Gas bubbles form on the
surface of Y.
Metal X is placed in a solution of metal ions Z2+.
No observable reaction. There is no observable reaction.
Which reaction would not occur spontaneously?
A X(s) + 2H+(aq) H2(g) + X
2+(aq)
B Z(s) + X2+(aq) X(s) + Z2+(aq)
C Z(s) + 2H+(aq) H2(g) + Z2+(aq)
D Y(s) + Z2+(aq) Z(s) + Y2+(aq)
9 An electric current of 4 A is passed for 200 minutes through
molten aluminium oxide
using inert electrodes. What will be the volume of gas liberated
at s.t.p.?
A 2.8 dm3 0.125 mol x 22.4
B 5.6 dm3 0.25 mol x 22.4
C 8.4 dm3 (3/4)x0.5 mol x 22.4
D 11.2 dm3
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10 The sketch below shows a physical property of seven
consecutive elements of
Periods 2 and 3 in increasing proton number.
Which physical property does this sketch depict?
A melting point
B atomic radius
C electronegativity
D electrical conductivity
11 T, U and V are oxides of Period 3 elements. The following
table lists some
properties of the oxides:
melting point / oC pH when mixed with water
T 920 13
U 1610 7
V 300 2
Which of the following represents the correct set of oxides?
T U V
A MgO Al2O3 P4O10
B SiO2 Al2O3 SO2
C Al2O3 MgO SO2
D Na2O SiO2 P4O10
proton number
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12 Which compound will give a poor yield when synthesised
directly from propene?
A 1-bromopropane B propan-2-ol
C 1-bromopropan-2-ol D ethanoic acid
13 Halogenoalkane is a starting material for synthesising
Grignard reagent, which is a
useful intermediate in organic synthesis as shown below.
Which of the following is not a possible product of the
following reaction?
A
B
C
D
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14 Compound X has the following structure:
Which of the following is formed when X is heated with iodine in
alkaline solution?
A
B
C
D
15 LSD is a stimulant drug that is often used by the Hippies in
the 1970s. Part of the
structure of LSD is shown below.
Which of the following properties can be deduced about LSD from
the partial
structure shown above?
A It is insoluble in aqueous nitric acid.
B It reacts with two moles of hydrogen bromide.
C It reacts with ethanoyl chloride to give off pungent white
fumes.
D It gives off a fishy smell when heated with aqueous
hydrochloric acid.
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For each of the following questions, one or more of the three
numbered statements 1 to 3 may be correct. Decide whether each of
the statements is or is not correct (you may find it helpful to put
a tick against the statements that you consider to be correct).
The responses A to D should be selected on the basis of
A B C D
1, 2 and 3 are
correct
1 and 2 only are correct
2 and 3 only are correct
1 only is
correct
No other combination of statements is used as a correct
response.
16 Which of the following statements regarding buffer solutions
are correct?
1 A CH3COOH / CH3COO buffer can be produced by adding a strong
acid to a
solution of CH3COO ions.
2 Within its effective buffering range, increasing the
concentrations of the
components of a buffer solution will increase its buffering
capacity.
3 If the pH of an acidic buffer solution is greater than the pKa
value of the acid, it will have a greater capacity to neutralise
added base than added acid.
17 Which statements are correct for a cell set up under standard
conditions using the
half-cells below?
Co2+(aq) / Co(s) E = 0.28 V Sn2+(aq) / Sn(s) E = 0.14 V
1 Electrons flow in the external circuit from Co electrode to Sn
electrode.
2 The concentration of Co2+(aq) will increase.
3 Reduction occurs at the Sn electrode.
18 Element Z forms a chloride ZCln. When 0.500 g of the chloride
reacts with excess
silver nitrate, 1.72 g of AgCl are formed.
Another 0.500 g sample of the chloride is heated strongly. When
the residue is
treated with an excess silver nitrate solution, only 1.57 g of
AgCl is precipitated.
Which of the following statements about the element are
correct?
1 Z burns in oxygen with a yellow flame.
2 The oxidation state of Z in the residue is +3.
3 Z is in Period 3.
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The responses A to D should be selected on the basis of
A B C D
1, 2 and 3 are
correct
1 and 2 only are correct
2 and 3 only are correct
1 only is
correct
No other combination of statements is used as a correct
response. 19 Which of the following naturally-occurring molecules
have all of the features listed
below?
At least five chiral carbons.
At least one secondary alcohol.
Either a carboxylic acid or a carboxylic acid derivative.
1
Thromoxane (TXA2)
2
Queuosine
3
Cortisol
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The responses A to D should be selected on the basis of
A B C D
1, 2 and 3 are
correct
1 and 2 only are correct
2 and 3 only are correct
1 only is
correct
No other combination of statements is used as a correct
response. 20 Citric acid, which causes the sharp taste of lemon
juice, has the following structure.
Which of the following reacts in a stoichiometric ratio with 1
mol of citric acid?
1 1.5 mol of Mg(s)
2 3 mol of Na2CO3(s)
3 4 mol of HCl(g)
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Raffles Institution 2013 9647/Y6/T3/13 [Turn Over
RAFFLES INSTITUTION 2013 Year 6 Term 3 Common Test
H2 Chemistry
COVER SHEET
Name: ( )
CT Group:
For Examiners Use Only
Section
Marks
A / 20
B
Q1 / 10
Q2 / 8
Q3 / 6
Q4 / 11
C
Q1 / 20
Q2 / 20
Penalty (Circle) 0 / 1
Total / 95
Percentage / 100
Grade
Penalty
Incorrect number of significant figures.
Missing OR wrong units.
Answers written in pencil.
Did not start question in Section C on a fresh page.
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Section B (35 marks)
This section consists of four questions. Answer all the
questions in this section in the spaces provided.
B1 Planning (P) The Matsutake mushroom is a delicacy added to
many Japanese foods. One of the
components isolated from these mushrooms is methyl cinnamate
which gives these mushrooms a rich and spicy aroma. Methyl
cinnamate can be prepared from cinnamic acid and methanol.
OH
O
O
O
+CH3OH+ H2O
cinnamic acid methanol methyl cinnamate
compound cinnamic acid methanol methyl cinnamate
molar mass / g mol1 148 32 162
boiling point / oC 300 65 261
melting point / oC 133 98 38
(a) 10.8 g of cinnamic acid was reacted with 30 cm3 of methanol,
which was in
excess, together with about 8 to 10 drops of concentrated
sulfuric acid. The volume of methanol used was about 10 times more
than the actual volume needed as a reactant. The addition of
concentrated sulfuric acid to the mixture was highly exothermic.
The reaction mixture was then heated under reflux for about five
hours before the unreacted methanol was recovered by
distillation.
(i) Write a plan for the preparation of methyl cinnamate.
In your plan, you should:
give a step-by-step description of the procedures you would use
to prepare methyl cinnamate, and
state the capacities of the apparatus used.
. . . . . . .
For
Examiners
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. . . . . . . . . .
(ii) Draw a labelled diagram of the assembled apparatus to show
how you
would recover the remaining methanol from the reaction mixture.
Indicate on your diagram the reading on the thermometer.
(iii) The excess methanol was used to drive the equilibrium
position to the right. Suggest another reason why methanol was used
in excess for this experiment.
. . .
[6]
For
Examiners
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(b) The methyl cinnamate was purified according to the following
procedure: 1. Transfer the reaction mixture containing methyl
cinnamate and unreacted
cinnamic acid to a separatory funnel.
2. Add 50 cm3 of ethoxyethane, CH3CH2OCH2CH3, to the separatory
funnel.
3. Add 50 cm3 of saturated sodium hydrogencarbonate solution to
the separatory funnel.
4. Shake the mixture and discard the lower aqueous layer.
5. Repeat Steps 3 and 4 until no more effervescence in the
aqueous layer is
observed. Suggest why the mixture must be washed with saturated
sodium hydrogencarbonate solution until no more effervescence was
observed.
[1] (c)
The ethoxyethane layer was collected and dried with anhydrous
calcium chloride. The ethoxyethane was then evaporated to recover
the crude methyl cinnamate, which was subsequently purified by
recrystallisation and air-dried. Two possible solvents, A and B can
be used for the recrystallisation of methyl cinnamate. The table
below gives data about the solubility of methyl cinnamate in
solvents A and B.
Solubility of methyl cinnamate /g per 100 g of solvent
Temperature / oC Solvent A Solvent B
10 6.0 2.0
70 11.0 9.5
During recrystallisation, 50 g of one of these solvents was
saturated with the methyl cinnamate at 70 oC and the solution was
then cooled at 10 oC.
tap
stopper
ethoxyethane layer
sodium hydrogencarbonate layer
separatory funnel
For
Examiners
Use
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(i) Explain why the use of solvent A, rather than solvent B,
would lead to a lower yield of recrystallised methyl cinnamate. . .
. .
(ii) Calculate the final mass of methyl cinnamate that would be
obtained if solvent B was used.
[2] (d) With reference to relevant data on page 12, explain how
you would check the
purity of your product.
[1]
[Total: 10]
For
Examiners
Use
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B2 (a) Iron ore is a mixture of iron(II) and iron(III) oxides.
The ore goes through a series of redox reactions in the blast
furnace to extract iron.
Iron(II) oxide can be reduced by carbon or carbon monoxide as
shown below.
Reaction Hr / kJ mol1 Gr
/ kJ mol1
(1) FeO + C CO + Fe +161 +114
(2) FeO + CO CO2 + Fe 11.01 5.64
(i) Given the above data, calculate the standard entropy change
of
reaction, Sr, of reactions (1) and (2).
(ii) Comment and explain the difference in the values obtained
in (a)(i).
. . . . . . . . .
For
Examiners
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(iii) During the extraction of iron, the interior of the blast
furnace has different temperatures as shown in the diagram below.
This results in different reducing agents reacting with the iron
ore in different regions. Using the information on page 16, deduce
which reactions, (1) or (2), will take place at 700 oC and 1500 oC
respectively. Write down the reaction number in the boxes
below.
[5] (b) Iron(III) oxide, Fe2O3, is also reduced by carbon
monoxide in the blast
furnace. Using the following data, draw an energy cycle and
calculate the standard
enthalpy change of reaction for the reduction of iron(III) oxide
by carbon monoxide to extract iron.
standard enthalpy change of formation of iron(III) oxide = 824
kJ mol1 standard enthalpy change of combustion of carbon monoxide =
283 kJ mol1
[3] [Total: 8]
Reaction ____
Reaction ____
700oC
1500oC
iron slag
hot air out
hot air in
iron ore and limestone
1900oC
hot air in
For
Examiners
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B3 Selective precipitation is a technique in which one ion is
selectively removed from a mixture of ions by precipitation. The
numerical values of the solubility product of the sparingly soluble
salts in water at 25 oC are given as follows:
Ksp of AgCl = 1.77 x 1010 ; Ksp of Ag2CrO4 = 1.12 x 10
12
A solution of AgNO3 is added slowly and continuously to a
solution containing Cl
(aq)
and CrO42(aq) of concentration 0.010 mol dm3 each.
It is assumed that the addition of AgNO3 solution does not
change the overall solution volume to any significant degree.
(a) Show that AgCl precipitates before Ag2CrO4.
[2] (b) Calculate the concentration of Cl when the first trace
of Ag2CrO4 precipitate
appears.
[1]
For
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(c) After the AgCl precipitate is removed and more aqueous AgNO3
is added to
the remaining solution, a suspension of reddish brown Ag2CrO4 is
obtained. With the aid of equations, describe and explain what
happens when dilute nitric acid is added to this suspension of
Ag2CrO4.
.. .. .. .. .. .. .. .. .. ..
[3]
[Total: 6]
B4 Use of the Data Booklet is relevant to this question. (a)
The standard electrode potential of bromate(V) ions in acidic
medium is represented by the equation:
2BrO3(aq) + 12H+(aq) + 10e Br2(aq) + 6H2O(l) E
= +1.52 V
(i) Draw a fully labelled diagram to show how the above standard
electrode potential may be determined.
For
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(ii) Use E data to predict and explain what might happen when a
solution of acidified bromate(V) ions is added separately to the
following reagents in and . Write balanced equations for any
reactions that occur.
Excess aqueous potassium iodide
... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
Acidified potassium dichromate(VI)
... ... ... ... ... ... ...
[6]
For
Examiners
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(b) The leadacid accumulator is a storage battery because it can
be recharged. It consists of a series of cells, and each cell
contains an electrolyte of sulfuric acid as well as two electrodes,
one made of lead and the other, lead dioxide. The relevant
reduction potentials are given below.
PbSO4(s) + 2e Pb(s) + SO4
2(aq) E= 0.13 V
PbO2(s) + 4H+(aq) + SO4
2(aq) + 2e PbSO4(s) + 2H2O(l) E = +1.47 V
(i) Write the overall equation for the reaction upon discharge,
and
calculate the voltage delivered by the battery if it contains a
series of 6 cells.
(ii) State the polarity (i.e. + or ) of the respective
electrodes by filling up the box below.
electrode polarity
Pb
PbO2
(iii) Suggest a reason why the battery is rechargeable.
... ... ...
(iv) Explain why the measurement of the electrolyte density can
be used
to indicate the extent of discharge of the cell.
... ... ...
[5]
[Total: 11]
For
Examiners
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Section C (40 marks)
This section consists of two questions. Answer all questions
from this section. Begin each question on a fresh page of
paper.
C1 This question is mainly about organic compounds that are
found in some animals
and bacteria.
(a) Mandelonitrile is synthesised and stored in special glands
by some species of millipedes such as Apheloria corrigata and
Pachydesmus crassicutis. When the millipede is attacked, the stored
mandelonitrile undergoes an enzyme-catalysed reaction to yield a
mixture of toxic hydrogen cyanide and benzaldehye, which is ejected
to ward off predators.
O
Henzyme
OH
CN
+ HCN
mandelonitrile benzaldehyde hydrogen cyanide
(i) The reverse of the above reaction can be carried out in the
laboratory using a trace amount of aqueous potassium cyanide.
Describe the mechanism of this reverse reaction.
Under suitable conditions, mandelonitrile can be converted into
compounds
W and X as shown in the reaction scheme below.
OH
CN
mandelic acid
Cl
ClOH
NH2 O
W mandelonitrile X
(ii) With reference to the different hybridisation states of the
nitrogen
atoms in the CN and NH2 groups, explain why mandelonitrile,
unlike compound W, is effectively neutral and not basic.
(iii) When one mole of compound X is treated with one mole
of
dimethylamine, (CH3)2NH, a neutral organic product Y is
obtained. Suggest the structure for Y and explain the different
reactivities of the two chlorine atoms in X.
(iv) In an experiment, 0.20 mol of compound X was added to 1 dm3
of
0.10 mol dm3 sodium hydroxide solution. Calculate the
approximate pH of the resultant solution formed, with reasoning
shown.
[10]
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(b) Benzaldehyde, present in the toxic secretion of the
Apheloria corrigata millipedes, is known to be repellent to ants.
When treated with concentrated sodium hydroxide, benzaldehyde
undergoes the following reaction first studied by Stanislao
Cannizzaro in 1853:
O
H
concentrated NaOH
O
O-Na+OH+
(i) Determine the oxidation number of each of the labelled
carbon atoms, , and , in the three compounds and hence, or
otherwise, state the type of reaction which occurs.
(ii) Using benzaldehyde as the reactant, the mechanism for
Cannizzaro reaction is shown below:
O
HOH
O-
-:OH
O
H
H
O
O-
O-
+
-OH
O-
O-
H + H2O
:O-
O-H +
H2O
O
O-
O-
+
O
O-
OH
+
Deuterium, D, is the
isotope of hydrogen.
With the aid of the above mechanism, suggest the
deuterium-containing organic product(s) that would be obtained for
each of the following reactions:
(1) O
Hconcentrated NaOD, D2O
(2) O
Dconcentrated NaOH, H2O
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(iii) Suggest suitable reagents and conditions to carry out the
following 3-step synthesis in which one of the steps must be the
Cannizzaro reaction. Show all intermediate products formed.
O
O
O
H
H
O [7]
(c) Compound L is produced by bacterial species such as
Bifidobacterium and Streptococcus. In the laboratory, it can be
obtained from a six-carbon compound K.
K does not react with sodium nor phenylhydrazine. Upon analysis,
it is found to contain 5.6% H and 44.4% O by mass.
When K is refluxed with aqueous sodium hydroxide and the
resultant mixture distilled, the distillate does not contain any
organic compound. Acidification of the residual mixture left from
the distillation yields L as the only organic compound. Warming 1
mole of L with alkaline aqueous iodine produces 1 mole of
ethanedioate ions and 1 mole of a yellow precipitate.
(i) Determine the molecular formula of K. (ii) Suggest a
suitable structural formula each for K and L. [3] [Total: 20]
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C2 Magainins are a class of proteins isolated from the African
Clawed Frog, Xenopus laevis, found to exhibit potent broad-spectrum
antimicrobial activity, and are evaluated for use as drugs for
treating diseases.
A major disadvantage of using peptide-based drugs is that their
properties may be lost in the body of the patient due to enzymatic
hydrolysis. This may be overcome by modifying the structure of the
amino acids used.
Typical proteins consist of -amino acids, so named because the
amino group is on
the -carbon atom, next to the carboxylic acid group.
An -amino acid, where R is the side group.
A magainin peptide may be modified using -amino acids. A -amino
acid has the
amino group on the -carbon atom, which is the second carbon atom
from the acid group.
A -amino acid, where R is the side group.
(a) Draw the structure of a tripeptide that consists of all
three of the following
-amino acids:
-leucine: R = CH2CH(CH3)2 -lysine: R = CH2CH2CH2CH2NH2 -glutamic
acid: R = CH2CH2COOH
[1] (b) Explain how a modified peptide synthesised from -amino
acids may be
resistant to enzymatic hydrolysis in the body. [1]
(c) A magainin protein can be modified by replacing some of its
-amino acids
with the corresponding -amino acids, with the same R groups.
Explain why such a modified protein exhibits similar biological
properties.
[2] (d) Describe with an aid of a diagram, the structure of the
alpha helix. [3] (e) Generally, helix structures of peptides
synthesised from -amino acids are
more stable than the helix structure of a typical peptide of
-amino acids. Suggest a reason for this observation.
[1]
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(f) Aspartic acid is one of the amino acids found in a magainin
peptide. Suggest a possible synthesis scheme of aspartic acid from
ethene.
[6] (g) The pKa values of aspartic acid are listed below:
pK1 = 1.95 pK2 = 3.71 pK3 = 9.66
(i) Sketch the titration curve when a solution containing the
following
species A+ is titrated with aqueous sodium hydroxide.
A+ (ii) Draw the structure of the most abundant species present
when the
pH of an aspartic acid solution is adjusted to 2.83. (iii)
Describe the movement of the species from part (ii) in an
electric
field. [4] (h) Suggest a simple chemical test to distinguish the
following two compounds.
X: CH3CH2CH2CONH2 and Y: CH3CH2CH2COO
NH4+
[2] [Total: 20]
END OF PAPER
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RAFFLES INSTITUTION 2013 Year 6 Term 3 Common Test
H2 Chemistry
COVER SHEET
Name: ( )
CT Group:
For Examiners Use Only
Section
Marks
C1a b / 17
C1c / 3
C2 / 20
Penalty
Incorrect number of significant figures.
Missing OR wrong units.
Answers written in pencil.
Did not start question in Section C on a fresh page.
C