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UNIVERSITY OF CANTERBURY
End of Year Examinations 2001
Prescription Number(s): CHEM112
Paper Title: General Chemistry B
Time Allowed: 11/2 HOURS
Number of pages: 13
Before commencing work, read the instructions on this page.
1. This is both your examination paper and your answer book. You may use the
blank page opposite for any additional working pertaining to that question.
2. Please ensure that your name has been entered in the appropriate spaces above.
3. ANSWER ALL QUESTIONS.
Total marks = 90: you should allocate 1 minute per mark.
NOTE: There is a Periodic Table on page 2.
1-4 5-7 8-10 11-12 13-15 Total
CHEM112
Periodic Table
1 2
H He
1.008 4.00
3 4 5 6 7 8 9 10
Li Be B C N O F Ne
6.94 9.01 10.8 12.01 14.01 16.00 19.0 20.2
11 12 13 14 15 16 17 18
Na Mg Al Si P S Cl Ar
23.0 24.3 27.0 28.1 31.0 32.1 35.5 39.9
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
39.1 40.1 45.0 47.9 50.9 52.0 54.9 55.9 58.9 58.7 63.5 65.4 69.7 72.6 74.9 79.0 79.9 83.8
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
85.5 87.6 88.9 91.2 92.9 95.9 (99) 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3
55 56 57-71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
Cs Ba see Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
132.9 137.3 below 178.5 181.0 183.9 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 (210) (210) (222)
87 88 89-103 104 105 106 107 108 109 110 111 112
Fr Ra see Rf Db Sg Bh Hs Mt
(223) (226) below (257) (260) (263) (262) (265) (266)
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
138.9 140.1 140.9 144.2 (147) 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.0 175.0
89 90 91 92 93 94 95 96 97 98 99 100 101 102 103
Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
(227) 232.0 (231) 238.1 (237) (242) (243) (247) (245) (251) (254) (253) (256) (254) (257)
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CHEM112
1. (8 marks)
Three methods are shown below for the conversion of benzene into benzoic acid.
Complete the scheme by supplying the missing reagents (A-E) and structures
(F-H).
A B
NO2 NH2
C NaNO2
CH3Cl HCl
AlCl3 0o C
F G
Br
Mg D E
dry ether
H
CO2H CN
(i) CO2 (i) NaOH /
(ii) H3O+ (ii) H3O+
2. (2 marks)
Draw the structures of the three resonance contributors to the Wheland
intermediate formed in the electrophilic bromination of benzene.
3 TURN OVER
CHEM112
3. (3 marks)
Cyclohexene reacts with hydrogen, in the presence of a catalyst, to give
cyclohexane. For this reaction H = -120 kJ mol-1. For the hydrogenation of
benzene to cyclohexane H = -210 kJ mol-1. Show how these values can be used
to obtain an estimate of the resonance stabilisation energy of benzene.
4. (2 marks)
The structure of the disaccharide maltose is shown below. Clearly identify with
arrows an acetal carbon and a hemiacetal carbon in the structure of maltose.
Which of these carbons undergoes a change of stereochemistry during the process
of mutarotation?
CH 2OH CH 2OH
O H O OH
OH OH
maltose
O H
HO
OH OH
4 TURN OVER
CHEM112
5. (3 marks)
The monocyclic sesquiterpene bisabolene (below) has recently been identified in
avocado fruit.
bisabolene
Identify clearly the isoprene units in the structure above. Identify with arrows the
bonds that represent the head-to-tail linkages. Circle the bond that represents the
extra C-C cross link.
6. (4 marks)
The structures of the amino acids alanine (ala) and serine (ser) are shown below.
H3C H HOH2C H
H2N CO2H H2N CO2H
ala ser
(a) Draw the structures of the form in which you would expect to find alanine at
low pH (e.g. pH 12)?
Low pH form High pH form
(b) Draw the structure of the dipeptide ser-ala and give the names of all other
dipeptides that could be formed using these two amino acids.
Structure of ser-ala Names of others
5 TURN OVER
CHEM112
7. (8 marks)
Shown below are a selection of natural products (A – N).
Which of these is:
(a) a quinoline alkaloid Ans:
(b) a monocyclic sesquiterpene Ans:
(c) a pyridine alkaloid Ans:
(d) a pentose sugar Ans:
(e) a disaccharide Ans:
(f) an indole alkaloid Ans:
(g) a dipeptide Ans:
(h) a tricyclic sesquiterpene Ans:
OH
H3CO
N H
HO HO N
H H OH
H2N N CO 2H
H OCH 3
O
N
leu-tyr (A) scoulerine (B)
conchonidine (C)
SH NH 2
H3C H H H H
H2N HO
N N CO 2H
H H
O O N
H
ala-gly-cys (D)
serotonin (E) zingiberene (F)
CHO
CH 3 HO H
O N N HO H
N H OH
H3C N H OH
HO O
O CH 3
CH 2OH
caffeine (G) D-allose (H) spathulenol (I) carvone (J)
CH 2OH CHO
H3CO NH 2 O OH H OH
CH 2OH OH
O HO H
HO O O H N
H3CO OH H H OH
OH Me
OCH 3 N CH 2OH
mescaline (K) OH lactose (L) cotinine (M) D-xylose (N)
6 TURN OVER
CHEM112
8. (10 marks)
The Ellingham Diagram shown below will be helpful for answering this question.
G, kJ (mol O2)-1
(a) Explain why the line on the Ellingham Diagram labelled ‘2NiO’ has a
positive slope whereas that labelled ‘2CO’ has a negative slope.
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CHEM112
(b) (i) Write a balanced equation for the formation of chromium metal from
its oxide using aluminium as the reducing agent.
(ii) Calculate the standard free energy change (G) per mol O2 for the
reaction in part (i) occurring at 1000 K.
(iii) Is this reaction spontaneous as written? Why?
9. (4 marks)
(a) Give the 4s, 3d electron configurations of:
(i) V(III)
(ii) Ni(0)
(b) What is the highest common oxidation state (oxidation number) of:
(i) Cr?
(ii) Sc?
10. (4 marks)
For the complex [Fe(SCN)(H2O)5]2+:
(a) What is the oxidation state (oxidation number) of Fe?
(b) What is the coordination number of Fe?
(c) What is the colour of the complex?
(d) What is the geometry of the complex?
8 TURN OVER
CHEM112
11. (10 marks)
(a) (i) Define the terms labile and inert as they are used in coordination
chemistry.
(ii) From the following list, name one metal ion which usually forms
highly labile complexes and one which forms extremely inert
complexes:
Pd2+ Fe3+ Co3+ Ni2+ V2+ Cu2+
highly labile:
extremely inert:
(b) Cisplatin (cis-PtCl2(NH3)2) is used to treat some cancers.
(i) Draw the cisplatin complex clearly showing its geometry.
(ii) The complex is ‘moderately inert’. Explain in detail how this is
important for the functioning of the complex as a cancer-treatment
drug.
Continue your answer on the following page
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CHEM112
Answer 11(b)(ii) cont’d..
12. (12 marks)
The spectrochemical series and a table showing complementary colours and their
wavelengths () are given below to aid in your answer to this question.
spectrochemical series:
I– N=N > S=S
(ii) N=O > N=N and N=O > O=O
(b) Suggest an explanation for why CH3C≡N is a commonly used solvent
whereas CH3C≡P is a highly reactive chemical.
END OF PAPER