Centre NumberSurnameOther namesCandidate Number AHS Examinations
Semester 4ChemistryAdvanced LevelUnit 5: General Principles of y I
, Equilibria and Further Organic Chemistry (including synoptic
assessment)April 2012 Time: 1 hour 40 minutesWrite your name
herePaper Reference6CH05/01You do not need any other
materials.Total MarksGrade
General Principles of Chemistry II Transition Metals and Organic
Nitrogen Chemistry (including synoptic assessment)
InstructionsUse black ink or ball-point pen. Fill in the boxes
at the top of this page with your name, centre number and candidate
number. Answer all questions. Answer the questions in the spaces
provided there may be more space than you need.InformationThe total
mark for this paper is 90. The marks for each question are shown in
brackets use this as a guide as to how much time to spend on each
question. Questions labelled with an asterisk (*) are ones where
the quality of your written communication will be assessed you
should take particular care with your spelling, punctuation and
grammar, as well as the clarity of expression, on these questions.
A data booklet is provided with this paper.AdviceRead each question
carefully before you start to answer it. Keep an eye on the time.
Try to answer every question.Check your answers if you have time at
the end. Check your answer if you have time at the end.
A37964H2012 Addu High School.
SECTION AAnswer ALL questions.For questions 110, in Section A,
select one answer from A to D and put a cross in the box.If you
change your mind, put a line through the box and then mark your new
answer with a cross.1. What is the value of E0 for the half-cell:
(1)MnO4- + 8H+ + 5e- Mn2+ + 4H2O A 1.50 V B 1.86 V C 1.44 V D 1.58
V2. Consider the standard voltaic (or galvanic) cell: Fe,Fe2+//
Ag,Ag+. Which answer identifies the cathode and gives the Eofor the
cell? (1) A Ag, 0.80 V B Fe, 1.06 V C Ag, 1.06 V D Fe, 1.94 V
3. Which of the following is the strongest oxidizing agent?
(1)
A Pb2+ B Ag+ C Cu2+ D Zn2+4. On the basis of the definition
which of these ions have an electronic configuration of a
transition metal. (1)5. A SC3+ B Zn 2+ C Cu+ D Cu2+6. Which
transition metal shows the greatest variation in possible oxidation
numbers(1)
A V B Cr C Mn D Fe6. Which of the following statements about
catalyst is true. (1) A Catalysts change the equilibrium position
of a reaction B Catalysts are always used to slow down reaction
rates C Catalysts are not consumed by the reaction they take part
in D D Catalysts can be recovered from a reaction and regenerated
by performing a simple chemical reaction7. What is meant by the
term 'ligand' ? (1) A A substance that can donate a lone pair of
electrons to form a dative bond B A substance that can accept a
lone pair of electrons to form a dative bond C A substance that can
donate lone pair of electrons to form hydrogen bond D A substance
that can accept a lone pair of electrons to form hydrogen bond
8. Given the list of ligands and their corresponding names,
choose the pair that disagrees. (1) A OH- hydroxo B CN- Cyanide C
Cl- Chloro D H2O Aqua 9. What is the oxidation number of the
central metal atom in the coordination compound [Pt(NH3)3Cl]Cl? (1)
A 1 B 2 C 3 D 410. When aqueous ammonia is added to a solution of
copper II sulphate the pale blue solution changes to a dark blue
colour. What is the formula of the complex formed? (1) A
[Cu(H2O)6]2+(aq) B [Cu(NH3)4(H2O)2]2+(aq) C [ Cu(NH3)2(H2O)4]2+(aq)
D [ Cu(NH3)6]2+(aq)11. Which statement about benzene is incorrect?
(1) A The empirical formula is C1H1 B The C6ring is planar. B The
CC-bonding is delocalized. D The reactivity reflects the presence
of C=C bond12. How many signals do you expect to see in the1H NMR
spectrum of benzene? (1) A 1 B 2 C 3 D 613. In the nitration of
benzene using a mixture of conc. H2SO4and conc. HNO3, the species
which initiates the reaction is . (1) A NO2 B NO+ C NO2+ D NO214.
The possible number of isomeric mono substituted benzene
derivatives is(1) A 4 B 3 C 2 D 115. The nitration of benzene
results in a mixture of different products. Select the odd one out.
(1) A nitrobenzene B 1,2-dinitrobenzene C 1,3,5-trnitrobenzene D
1,3 dinitroenzene16. Which statement about phenol is correct
(1)
A. No catalyst is required for its reaction with bromine B It
behaves like a typical alcoholC. It is a crystalline solid at 298 K
D It reacts with NaOH to give sodium phenoxide17. The reaction of
aniline with bromine water gives: (1)A 2-bromoaniline B
4-bromoaniline C 2,4-dibromoaniline D 2,4,6-tribromoaniline18.
Ethanamine , CH3CH2NH2, reacts with ethanoyl chloride to
form(1)
A CH3CH2NH3+Cl- B CH3CH2NH CH2CH3 C CH3CH2NHCOCH3 D
CH3CH2COCH319. The gas evolved when methylamine reacts with nitrous
acid is(1) A NH3 B N2 C H2 D C2H620. Organic solids are often
purified by recrystallization. This technique works on the basis
that A the impurities must be insoluble in the solvent used. B the
impurities must react with the solvent used.C the impurities
crystallize first when the hot solution is cooled.D the cooled
solution is saturated with the desired material but not with the
(Total for section A = 20 Marks)SECTION BAnswer ALL
questions.Answer the questions in the space provided.21. The
pain-relieving drug ibuprofen has the formula(a)The drug ibuprofen
can be synthesised from benzene by the route shown below.
(i) Name the type and mechanism of the reaction in Step A, and
suggest a suitable reagent and catalyst. Type and mechanism:
(3)
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Name of the reagent for Step A
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Catalyst
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(ii) Give the mechanism for the reaction in step 1, including
the equation for the formation of the secies responsible for this
reaction. Equation for formation of the reacting species(1)
Mechanism(3)
(b) The alkyl benzene formed in step A generally reacts in a
similar way to benzene but faster, as the ring is said to be
activated.
(i) Explain how the presence of alkyl group activates the
benzene ring.(1)
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(ii) Use your answer to (i) to explain why alkyl benzene reacts
faster.(1)
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Step C is a reduction.Give ONE reason why lithium
tetrahydridoaluminate,LiAlH4, is preferred to hydrogen as a
reducing agent in this reaction (2)
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(d) A sample of the final product was analysed by combustion. 1.00
g was burnt in oxygen. It produced 2.78 g carbon dioxide and 0.786
g water.State the molecular formula of ibuprofen and show that
these results are consistent with it(4) Molecular
formula------------------------------------------------------------------------------------------------------------------------------------------------
Calculations:-
(e) Ibuprofen can be analysed by instrumental methods. The
infrared spectra of ibuprofen and two other drugs, aspirin and
paracetamol, not necessarily in that order, are shown opposite.
Ibuprofen Paracetamol, Aspirin
(i) Explain, referring to the structure of each molecule, why
infrared spectroscopy is not a good technique to distinguish
aspirin from ibuprofen.(1)
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Deduce which of X, Y or Z is the infrared spectrum of paracetamol,
giving a piece of evidence from the spectrum you select.
Reasoning: (2)
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(i) Ibuprofen and aspirin can be distinguished using their mass
spectra.A line at mass/charge ratio 57 occurs only in the mass
spectrum of ibuprofen.Give the formula of the ion which produces
this line.(1)
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Suggest the mass/charge ratio of one line which occurs in the mass
spectrum of aspirin but not ibuprofen, and the formula of the
species which produces it.(1)
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Ibuprofen is almost insoluble in aqueous solutions at pH 3 but if
the pH is raised to8then the ibuprofen becomes reasonably soluble.
Account for these observations.(3)
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(h) Under the appropriate conditions ibuprofen reacts with
ethanol to produce a substance with a characteristic odour.(i)
Identify the functional group in ibuprofen that would react with
the ethanol. (1)
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Suggest the conditions needed for the reaction to take place and
identify the
product.(1)------------------------------------------------------------------------------------------------------------------------------------------------
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(Total Question 21 = 25 Marks)22. Alanine, 2-aminopropanoic acid,
is the simplest chiral amino acid found in nature and is optically
active.
(a) (i)Explain the meaning of the term chiral.(1)
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(ii) How is optical activity detected
experimentally?(1)------------------------------------------------------------------------------------------------------------------------------------------------
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(iv) If alanine is made from propanoic acid the product mixture
does not show optical activity. Explain why this is
so.(2)------------------------------------------------------------------------------------------------------------------------------------------------
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(b) Alanine reacts with both acids and bases. Give the
structural formulae of the compounds you would expect if alanine
reacts with (1)hydrochloric acid
sodium hydroxide(1)
(c)Alanine has a high melting temperature of 300 C, much higher
than would be expected for the structure given at the start of the
question.Draw the structure that is actually present in the solid,
and explain why the melting temperature is so high.Structure
(1)
Explanation (1)
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(Total Question 22 = 8 Marks)21. The following scheme shows some
reactions of chromium compounds in aqueous solution.
[Cr(H2O)6]3+ Reaction 7Cr2O72- CH3CH2OH + H2SO4 (aq) Reaction 1
Reaction 6 NaOH(aq)Zn + H2SO4 (aq) Grey- Green precipitate A Blue
solution C
Reaction 2 Reaction 4Excess NH3(aq)
[Cr(OH)6]3- [Cr(NH3)6]3+ Reaction 3 Reaction 5
EDTA 4-
CrO42- Chromium containing species
(a) (i) Explain why the [Cr(H2O)6]3+ ion is coloured.(3)
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(b) Identify the grey-green precipitate A formed in reaction 1.
Write an equation for this reaction.Green
precipitate(1)------------------------------------------------------------------------------------------------------------------------------------------------
Equation :(1)
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(i) Identify a reagent for Reaction 2.(1)
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(ii) Deduce the oxidation state of chromium in CrO(1)
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(iii) Identify a reagent needed for Reaction 3. (1)
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(i) Draw the structure of the chromium-containing species C formed
in Reaction 5. Indicate the charge on species C.(2)
(ii)Explain, by reference to the changes in bonding, why the
enthalpy change, H, in Reaction 5 is close to
zero.(1)------------------------------------------------------------------------------------------------------------------------------------------------
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(iii) Explain why the free-energy change, G, for Reaction 5 is
negative.(2)
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Identify the chromium-containing species present in the blue
solution D formed in Reaction 6 and state the role of zinc in its
formation.Chromium species formed(1)
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Role of zinc in this reaction(1)
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(f) Two organic compounds are formed in Reaction 7. One of these
compounds has a low boiling point and can be distilled readily from
the reaction mixture. The other compound has a higher boiling point
and is the main organic product formed when the reaction mixture is
refluxed.(i) Identify the organic product which has a low boiling
point.(1)
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(ii) Identify the main organic product formed when the mixture
is refluxed.(1)
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(Total For Question 23 = 17 Marks) (Total for section B = 50
Marks)
SECTION C
The hexagonal ring structure of benzene was first suggested by
Kekul in 1865, but the nature of the bonding was not elucidated
until the 1930s. This question concerns aspects of the structure of
benzene. (a) The enthalpy of hydrogenation of cyclohexene to give
cyclohexane is 120 kJ mol1 and that of cyclohexa-1,4-diene is 240
kJ mol1 .
(i) What would you expect the value of the enthalpy of
hydrogenation to be for the hypothetical molecule
cyclohexa-1,3,5-triene, on the basis of these data? (1)
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(ii) The hydrogenation enthalpy of benzene to give cyclohexane
is 208 kJ mol1. Use your result from (i) and this information to
draw an enthalpy level diagram to show that benzene is
thermodynamically more stable than the hypothetical
cyclohexa-1,3,5-triene. (2) Label the stabilisation energy on your
diagram.
(iii) Explain in terms of bonding why benzene would be less
reactive with bromine than the hypothetical
cyclohexa-1,3,5-triene.(2)
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(b) Both cyclohexa-1,3,5-triene & benzene reacts with
bromine in an appropriate solvent to form the same product (i) Name
the type & mechanism of the reaction of cyclohexene with
bromine and name the product of the reaction(2)
Type
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Mechanism------------------------------------------------------------------------------------------------------------------------------------------------
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(ii) Explain why benzene does not undergo reactions with the
same mechanism as in (b)(i).(2)
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(iii) Name the condition necessary for benzene to undergo the
same type of reaction with bromine.(1)
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(iv) Name the mechanism for the reaction in which benzene
undergoes but cyclohexene does not. (1)
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(v) Draw the structural formulae of the product formed in this
reaction (1)
(d) This question concerns the reaction scheme shown below.
(i) Give the reagents needed for the reduction of nitrobenzene
in step 1.(2)
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(ii) In step 1 when reduction is complete, the reaction mixture
must be made alkaline to liberate the phenylamine product. Give the
equation for the reaction that occurs when the alkali is
added.(1)------------------------------------------------------------------------------------------------------------------------------------------------
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(iii) In step 2, a mixture of sodium nitrite and hydrochloric acid
is used at a temperature between 0 C and 10 C. Explain why the
reaction mixture must not be cooler or warmer than these
limits.(2)
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(iv) Complete the structure of the cation in compound A, showing
all the bonds.(1)
(v) In step 3, compound A reacts with phenol. What conditions
are necessary?(1)
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Draw the structure of compound B, showing all the bonds. (1)
(Total for section C = 20 Marks)
AHS/Dept of Science / Semester- 4(April 2012)/ Grade
12/Chemistry - Unit 5 18 of 18
