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GNC502S - GENERAL CHEMISTRY 1B - 2ND OPP - JANUARY 2025 |
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n Am I BI A uni VER s ITY
OF SCIEnCE AnDTECHnOLOGY
FacultyofHealthN, atural
ResourceasndApplied
Sciences
Schoolof Natural and Applied
Sciences
Departmentof Biology,
Chemistryand Physics
-r
13JacksonKaujeuaStreet T: +264612072012
Private Bag13:lBB
F: +264612079012
Windhoek
E: dbcp@nust.na
NAMIBIA
W: www.nust.na
QUALIFICATION: BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC
COURSE: GENERAL CHEMISTRY lB
LEVEL:5
COURSECODE: GNC502S
DATE: JANUARY 2025
DURATION: 3 HOURS
SESSION: 1
MARKS: 100
SECOND OPPORTUNITY/ SUPPLEMENTARY: QUESTION PAPER
EXAMINER:
MODERATOR:
DR MARIUS MUTORWA
PROF LAMECH MWAPAGHA
INSTRUCTIONS:
1. Answer ALL the questions.
2. Write clearly and neatly.
3. Number the answers clearly
4. All written work must be done in blue or black ink and sketches can be done in
pencil.
5. No books, notes and other additional aids are allowed.
PERMISSIBLE MATERIALS
Non-programmable calculators
ATTACHMENTS
1. Useful Constants Data
2. Periodic Table
This paper consists of twelve (12) pages including this front page.
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,SECTION A:
[GOMARKS]
QUESTION 1: MULTIPLE CHOICE QUESTIONS
There are 20 multiple choice questions in this section. Each question carries 3 marks. Answer
ALLquestions by selecting the letter of the correct answer, even if you think there is another
possible answer that is not given.
1. NaOH + HCI
A. Na(OH)2 + H2
B. NaCl+ H2
C. NaCl+ H20
D. NaCl + H2+ 02
2. Phosphoric acid has the formula:
A. H2P03
B. H2P04
C. H3PQ4
D. H3P03
3. Which of the following could be added to a solution of sodium acetate
(CH3COONa)to produce a buffer?
A. Potassium acetate
B. Sodium chloride
C. Acetic acid
D. None of the above
4. In a reaction between CuS04(s)and Zn(s):
A. Zinc experiences an increase in oxidation state
B. Cu undergoes oxidation
C. Zn undergoes reduction
D. All of the above
General Chemistry 1B (GNCS02S)
2nd Opportunity January 2025
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5. Ascorbic acid (CGHsOGis) a common antioxidant that protects our bodies against
radicals. In the redox equation below that occurs in our stomach, which of the
following pairs identifies the reducing and oxidizing agents, respectively?
A. CGHsOG& NOz
B W&NOz
C. C5HsOG& W
D. W & NO2
6. Which of the following half reactions are balanced?
A. c1O-+ H2O+ e- Cl2+ 2OH-
B. 2 c1O-+ H2O+ 2e- Cb + 3OH-
c. 2 cio- + 2 H2O+ 2e- Cl2+ 4OH-
D. cio- + H2O+ e- Cb+ 2OW
7. What is the order of the reaction with respect to NO?
A. 0
B. 1
C. -1
D. 2
8. If the concentration of NO is doubled and that of and H2 is constant, the rate of the
reaction would:
A. Increase two fold
B. Increase four fold
C. Decrease two fold
D. Decrease four fold
General Chemistry 1B (GNC502S}
2nd Opportunity January 2025
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9. The reaction of elemental chlorine with ozone occurs by the two-step process shown
below:
I. Cl + 03 CIO + 02
II. CIO + 0 Cl+ 02
Which of the statements below is true regarding this process?
A. Cl is a catalyst
B. 03 is a catalyst
C. CIO is a catalyst
D. 02 is an intermediate
10. For the reaction:
Which one of the following is the correct expression for Kc?
A. Kc= [CO2]
B. Kc = [C02][H20]
C. Kc= [C02][H20][Na2C03]/[NaHC03)2
D. Kc= [C02][NaiC03]/[NaHC03]2
11. For which of the following reactions does Kc= Kpat 25°C?
A. 2NH3(g) + C02(g) =. N2CH40(s)+ H20(g)
B. 2NBr3(s) =. N2(g) + 3Br2(g)
C. 2KCI03(s) =. 2KCl(s) + 302(g)
D. CuO(s) + H2(g) =.Cu(/)+ H20(g)
12. Which of the following statements correctly describe the basic concepts and uses of
VSEPRtheory:
I) The VSEPRtheory is used for estimating bond angles.
II) The VSEPRtheory is used for predicting electronegativities.
Ill) The VSEPRtheory is helpful in predicting polarity.
IV) The VSEPRtheory states that electron pairs repel each other.
V) The VSEPRtheory uses valence electron counting for structure prediction.
General Chemistry 18 (GNC502S)
2nd Opportunity January 2025
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A. I), II), Ill), IV)
B. I), 11),IV), V)
C. I), 11),111)V, )
D. I), Ill), IV), V)
13. What is the correct molecular geometry for SeBr3+?
A. trigonal pyramidal
B. tetrahedral
C. trigonal planar
D. T-shaped
14. Which is NOT a valid resonance structure for the anion in the box below?
15. In the following compound, indicate the formal charge on all atoms except hydrogen,
from left to right.
H-c-N=c-o:
A. Carbon= O; Nitrogen= -1; Carbon= +1 and Oxygen= 0
B. Carbon= O; Nitrogen= -1; Carbon= 0 and Oxygen= -1
C. Carbon= O; Nitrogen= O; Carbon= 0 and Oxygen= -1
D. Carbon= O; Nitrogen= +1; Carbon= 0 and Oxygen= -1
General Chemistry 18 (GNC502S)
2nd Opportunity January 2025
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16. Which molecules contain both covalent and ionic bonds?
CH30H
I
Na2C03
II
N~Cl
III
A. I and II
B. II and IV
C. I, II and IV
D. II and Ill
NaCl
IV
17. Which of the following compounds do not contain an SP3 hybridized oxygen atom?
A. Ketones
B. Alcohols
C. Ethers
D. Esters
E. Water
18. Capsaicin is the spicy component of hot chilli peppers, and its structure is given below.
What is the correct molecular formula for this interesting molecule?
capsaicin
(spicy component of hot peppers)
A. C1sH21N03
B. C1sH2sN03
C. C1sH30N03
D. CisH2sN03
General Chemistry 1B (GNC5025)
2nd Opportunity January 2025
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19. Which of the following has the largest radius?
A. Se2-
B. Kr
C. Rb+
D. Br-
20. The IUPAC name of the compound below is:
A. 2,6-dimethyl-4-isopropyldecane
B. 2,6-dimethyl-2-chloro-4-isopropyloctane
C. 2,6-dimethyl-4-(1-methylpropyl)decane
D. 2,6-dimethyl-4-(3-methylpropyl)decane
END OF SECTIONA
General Chemistry 1B (GNC502S)
2nd Opportunity January 2025
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.SECTION B:
QUESTION 2
i) Find the oxidation numbers of the indicated atom in each of the following:
a. sin soi-
[40 MARKS)
[12)
(2)
(2)
(2)
ii) Balance the following half reactions:
a. Croi-(aq) Cr(OH}3(s)in basic medium
(3)
b. HNO2(aq) NH4+(aq)in acidic medium
(3)
QUESTION 3
[8]
A buffer solution contains 0.25 M NH3(Kb= 1.8 x 10-5 ) and 0.40 M NH4CI. Calculate the pH
of the solution.
QUESTION 4:
[10)
Methyl nitrate, CH3NO3,is used a rocket propellant. One of the nitrogen-to-oxygen bond
length is 136 pm and the other two are 126pm.
a. Draw the most stable Lewis structure of the molecule.
(3)
b. What is the hybridization state of the carbon atom and the nitrogen atom based on
Valence bond Theory?
(4)
c. Which set of hybrid orbitals are used to form the C-N bond?
(2)
d. What is the bond angle between the O-N-O bonds?
(1)
General Chemistry 1B {GNC502S)
2nd Opportunity January 2025
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QUESTION 5:
[10)
a. Enalapril is currently in clinical trials for congestive heart failure, and its structure is given
below.
OH
Enalapril
i. What is the correct molecular formula for this interesting antihypertensive
agent?
(2)
ii. Identify the functional groups present in Enalapril.
{5)
b. With reference to compound W drawn below, identify each of the compounds X - Z as
an isomer, resonance structure or neither.
{3}
w
i.
X
General Chemistry 1B (GNC502S)
2nd Opportunity January 2025
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ii.
y
iii.
z
END OF QUESTION PAPER
General Chemistry 1B (GNC502S)
2nd Opportunity January 2025
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2 Pages 11-20 |
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USEFULCONSTANTS:
Gas constant, R = 8.3145 J · mo1-1 · K-1
= 0.083145 dm 3 · bar· mo1-1 · K-1
= 0.08206 L atm mo1-1 · K-1
1 Pa· m3 = 1 kPa.L = 1 N · m = 1 J
1 atm = 101 325 Pa= 760 mmHg = 760 torr
Avogadro's Number, NA= 6.022 x 1023 mo1-1
Planck's constant, h = 6.626 x 10-34 Js
Speed of light, c = 2.998 x 108 ms-1
General Chemistry 1B (GNC502S)
2nd Opportunity January 2025
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n Am I BI A uni VER s ITY
OF SCIEnCE
FacultyofHealthN, atural
ResourceasndApplied
Sciences
13JacksonKaujeuaStreet T: +264612072012
PrivateBag13388
F: +264612079012
Windhoek
E: dbcp@nust.na
NAMIBIA
W: www.nust.na
Schoolof NaturalandApplied
Sciences
DepartmenotfBiology,
ChemistrayndPhysics
h)'drOQen
1
H
1.0079
Nlhlum
3
Li
ber)1lium
4
Be
6.941
sodium
11
Na
9.0122
m:JQnesi.Jm
12
Mg
22.990
potassium
19
K
24.Y.i5
C:lfcillll
20
Ca
scandium
21
Sc
liloni.Jm
22
Ti
VOOJdi.Jm chromium
23
24
V Cr
mongnnese
25
Mn
39.098
rubidium
37
Rb
40.078
slronlium
38
Sr
44.956
yllrium
39
y
47.867
zirconium
40
Zr
50.942
51.996
54.938
niobium molybdenum teclinelium
41
42
43
Nb Mo Tc
85.468
caesium
55
Cs
1?,2.91
lr.incium
87
Fr
12231
87.62
b~rium
56
Ba
137.33
radium
88
Ra
12261
57-70
*
89-102
**
88.906
luleli.Jm
71
Lu
91.224
holnlllll
72
Hf
92.906
tJnloiUm
73
Ta
95.94
tungsten
74
w
174.97
178.49
180.95
183.84
lawrencium rulherfordlum duboium seaborgium
103
104
105
106
Lr Rf Db Sg
12621
12611
12621
12661
1981
rhenium
75
Re
186.21
bohrium
107
Bh
12641
Iron
26
Fe
55.845
rulhenium
44
Ru
101.07
osmium
76
Os
190.23
hJSSilffll
108
Hs
12691
boron
5
B
c:irton
6
C
nllro;ien
7
N
10.811
:llun1inlum
13
Al
12.011
sfficon
14
Si
14.007
phosphorus
15
p
co~oll
27
Co
nickel
28
Ni
copper
zinc
29
30
Cu Zn
26.982
gallium
31
Ga
28.086
30.974
1Jerm..1ni.Jm :irsenlc
32
33
Ge As
58.933
rho:llum
45
Rh
58.693
palkldium
46
Pd
63.546
sliver
47
Ag
65.39
codmlum
48
Cd
69.723
Indium
49
In
72.61
lln
50
Sn
74.922
nnllmony
51
Sb
102.91
irkli.Jm
77
Ir
106.42
plollnum
78
Pt
107.87
Qokl
79
Au
112.41
mercury
80
Hg
114.82
lhOili.Jm
81
Tl
118.71
lead
82
Pb
121.76
blsmuu,
83
Bi
192.22
195.08
196.97
200.59
mellnerPJm ununnillum unurM.Jniumununbltrn
109
110
111
112
Mt UunUuuUub
204.38
207.2
ununqu~ium
114
Uuq
208.98
12&e1
12711
12721
12771
12891
ox,-gen
8
0
15.999
Stdlur
16
s
32.065
seleni.Jm
34
Se
78.96
lelurlum
52
Te
127.clO
polonium
84
Po
12091
fluorine
9
F
18.998
chlorine
17
Cl
35.453
b!omine
35
Br
79.904
Iodine
53
I
126.90
ostollne
85
At
12101
helPJm
2
He
4.0026
nron
10
Ne
20.180
:irgon
18
Ar
39.948
kryplon
36
Kr
83.80
xenon
54
Xe
131.29
radon
86
Rn
12221
* Lanthanide series
**Actinide series
lanlMnum
57
La
138.91
oclinlum
89
Ac
12271
cerium
58
Ce
140.12
lhoriJm
90
Th
232.04
pr~seodymiurr neodymium promethium
59
60
61
Pr Nd Pm
140.91
144.24
r:,rolaclini.Jm u-onlum
u 91
92
Pa
11451
n~ptunium
93
Np
231.(14 238.03
12371
samJrium
62
Sm
15(1.36
plutonium
94
Pu
12441
europium gadoinium
63
64
Eu Gd
151.96
157.25
nrneri.::ium curium
95
96
Am Cm
12431
12471
terbium
65
Tb
158.93
berkelium
97
Bk
12471
d1-sprosium hotmPJm
66
67
Dy Ho
162.50
164.93
callornlum einsteinium
98
99
Cf Es
12511
12521
erbium
68
Er
lhtdhrn 1·llerbium
69
70
Tm Yb
167.26
168.93
173.04
fermium mendelevium nobelitm
100
101
102
Fm Md No
12571
12581
12591