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GNC502S - GENERAL CHEMISTRY 1B - 1ST OPP - NOVEMBER 2024 |
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f
nAmI Bl A un IVERSITY
OF SCIEnCE AnDTECHnOLOGY
FacultyofHealthN, atural
ResourceasndApplied
Sciences
Schoolof NaturalandApplied
Sciences
Departmentof Biology,
ChemistryandPhysics
13JacksonKaujeuaStreet T: +264612072012
Private Bag73388
F: +264612079012
Windhoek
E: dbcp@nust.na
NAMIBIA
W: www.nust.na
QUALIFICATION: BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC
COURSE: GENERAL CHEMISTRY lB
DATE: NOVEMBER 2024
DURATION: 3 HOURS
LEVEL:5
COURSECODE: GNC502S
SESSION: 1
MARKS: 100
EXAMINER:
MODERATOR:
FIRST OPPORTUNITY: QUESTION PAPER
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 fourteen (11) pages including this front page.
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-
SECTION A:
(60 MARKS]'
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. The rate law for a reaction is rate= k[A]2[B]. Which of the following mixtures of reactants
will give the smallest initial rate?
A. 1.0 M [A], 1.0 M [Bl
B. 2.0 M [A], 0.50 M [Bl
C. 0.50 M [A], 0.50 M [BJ
D. 0.125 M [A], 3.0 M [Bl
2. The reaction of NO and 02 produces N02.
NO(g) + 02(g) N02(g)
The reaction is second-order with respect to NO(g) and first-order with respect to 02(g). At a
given temperature, the rate constant, k, equals 4.7 x 102 M- 2s-1. What is the rate of reaction
when the initial concentrations of NO and 02 are 0.025 Mand 0.015 M, respectively?
A. 2.6 x 10- 3 M/s
B. 4.4 x 10-3 M/s
C. 0.18 M/s
D. 2.0 x 10-s M/s
3. How are the exponents in a rate law determined?
A. They are equal to the inverse of the coefficients in the overall balanced chemical
equation.
B. They are determined by experimentation.
C. They are equal to the coefficients in the overall balanced chemical equation.
D. They are equal to the reactant concentrations.
General Chemistry 1B (GNC502S)
l51 Opportunity November 2024
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4. In a first-order reaction, the half-life is 144 minutes. What is the rate constant?
A. 8.02 x 10-s s-1
B. 4.81 x 10-3 s-1
(. 1.16 X 10-4 S-l
D. 5980 s-1
5. Which statement concerning relative rates of reaction is correct for the chemical
equation given below?
A. The rate of disappearance of CH30H is equal to the rate of disappearance of 02.
B. The rate of disappearance of CH30H is two times the rate of appearance of H20.
C. The rate of appearance of H20 is two times the rate of appearance of CO2.
D. The rate of disappearance of CH30H is half the rate of appearance of CO2.
6. Which of the following statements is/are CORRECT?
A. For a chemical.system, if the reaction quotient (Q) is greater than K, reactant must
be converted to products to reach equilibrium.
B. For a chemical system at equilibrium, the forward and reverse rates of reaction
are equal.
C. For a chemical system at equilibrium, the concentrations of products divided by
the concentrations of reactants equals one.
D. None of the above
7. Write the expression for Kfor the reaction below:
Al3+(aq) + 4 OW(aq) Al(OH)4-(aq)
[Al3+ ][Off]
K=~--~
A.
[ Al(OH)~]
l [ Al(OH):
r K = -------,-
B.
[ Off
General Chemistry 1B {GNC502S)
rt Opportunity November 2024
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[ Al(OH)~]
r K=-----
[ Al3 + )[ Off
C.
r [ Al3 + ][ OH-
K=-----
D.
[ Al(OH)~]
8. What is the H3Q+concentration in 0.0013 M LiOH(aq) at 25 °C? (Kw= 1.01 x 10- 14)
A. 7.7 X 10- 12 M
B. 8.7 X 10- 12 M
C. 10.6 X 10- 12 M
D. 5.6 X 10- 12 M
9. Write a balanced chemical equation which corresponds to the following equilibrium
constant expression.
A. PbF2{s)~Pb 2+(aq) + 2 F-(aq)
B. PbF2(aq) ~Pb(s) + F2(aq)
C. Pb(s) + F2(aq) ~PbF2(aq)
D. PbF+(aq) + F-(aq) ~PbF2(aq)
10. If the reaction quotient, Q, is greater than Kin a gas phase reaction, then
A. The chemical system has reached equilibrium.
B. The reaction will proceed in the backward direction until equilibrium is
established.
C. The reaction will proceed in the direction that increases the number of gas phase
particles.
D. The reaction will proceed in the forward direction until equilibrium is established.
General Chemistry 1B (GNC502S)
l51 Opportunity November 2024
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11. Balance the following oxidation-reduction
Mno4-(aq} +
occurring in acidic solution.
Mn 2+(aq} + Co3+(aq}
A. Mno4-(aq} + 8W(aq) + 5Co 2+(aq) Mn 2+(aq) + 4H20(I) + 5Co3+(aq)
B. Mn04-(aq) + 8W(aq) + Co2+(aq) Mn 2+(aq) + 4H20(I) + Co3+(aq)
C. Mno4-(aq) + 4H2(g) +
Mn 2+(aq) + 4H20(I) + 5Co3+(aq)
D. Mno4-(aq) + 8W(aq) + 2Co2+(aq) Mn 2+(aq) + 4H20(I) + 2Co3+(aq)
12. In ionic bond formation, the lattice energy of ions ___
charges ___
and the radii ___
_
A. Increases, decrease, increase
B. Increases, increase, increase
C. Decreases, increase, increase
D. Increases, increase, decrease
as the magnitude of the ion
13. There are ____
A. 18
B. 20
C. 26
D. 32
valence electrons in the Lewis structure of CH30CH2CH3.
14. A valid Lewis structure of ____
A. Poi-
B. SiF4
C. CF4
D. SeF4
cannot be drawn without violating the octet rule.
15. How many structural isomers can be drawn for a molecule with formula CsH10?
A. 7
B. 8
C. 10
D. 12
General Chemistry 1B (GNC502S)
1st Opportunity November 2024
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16. Give the IUPAC name for the following structure.
A. 3-ethyl-2methylheptane
B. 5-isopropyloctane
C. 4-isopropyloctane
D. 2-methyl-3-propylheptane
17. What is the electron configuration for the Fe3+ ion?
A. [Ar]4s13d6
B. [Ar]4s03d 7
c. [Ar]4s 03d5
D. [Ar]4s23d9
18. Using the VSEPRmodel, the molecular geometry of the central atom in
tetrafluoroborate ion is ___
_
A. square pyramidal
B. square planar
C. trigonal bipyramidal
D. octahedral
19. After drawing the Lewis dot structure of HOCIO2,pick the INCORRECTstatement of the
following.
A. The oxygen bonded to the hydrogen has two lone pairs.
B. The oxygens not bonded to hydrogen have three lone pairs.
C. The O-CI bonds are all double bonds.
D. The H-O bond is a single bond.
General Chemistry 1B (GNC502S)
1'1 Opportunity November 2024
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20. Which of the pairs of molecules below have the same hybridization on the central atom?
(The central atom is underlined in each molecule.)
A. ~02, ~H4
B.H2~0,BeH2
C. ~Cl3, Hf:!O
D. f:!H3, Hf:!O
END OF SECTION A
General Chemistry 1B (GNCS02S)
pt opportunity November 2024
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SECTION B:
[40 MARKS]
QUESTION 2
[12]
2.1 Sucrose is oxidised to CO2& H2O,and the enthalpy change for reaction is:
'1rH0 = -5645kJ/mol-rxn
What is the enthalpy change when 5.00 g of sugar is burned under constant pressure? (4)
2.2 Suppose you want to know the enthalpy change for the formation of methane from
solid carbon and hydrogen gas:
(8)
Equation 1: C (s) + 02 (g) CO2(g)
Equation 2: H2(g) + ½ 02 (g) H2O(I)
Equation 3: CH4(g) + 2 02 (g)
(g)+ 2 H2O(I)
'1rH1°= -393.5 kJ/mol-rxn
'1rHi° = -285.8 kJ/mol-rxn
'1rH2°= -890.3 kJ/mol-rxn
Use this information to calculate '1rH0 for formation of methane from its elements.
QUESTION 3
[8]
3.1 In a NaOH solution [oH-] is 2.9 x 10-4 M. Calculate the pH of the solution.
(2)
3.2 Calculate the pH of a:
a) 1.0 x 10-3 M HCI solution
(2)
b) 0.020 M Ba(OH)2solution
(4)
QUESTION 4:
[10)
Consider the Lewis structure for ethyl acetate below, used as a solvent and aroma enhancer.
H :O:
HH
H-C1-CI -20-1C1-C~-.H I I
HI
HI HI
General Chemistry 1B (GNC502S)
1'1 Opportunity November 2024
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4.1 How many valence electrons are used to make the sigma bonds in the molecule? (2)
4.2 What is the hybridization at each of the atoms (Cl, C2 and 03) which are numbered? (6)
4.3 Identify the functional groups in the following molecules.
(2)
0
(b)
II
NH2
QUESTION 5:
[10]
The lactic acid molecule, CH3CH(OH)COOHg, ives sour milk its unpleasant, sour taste.
a) Draw the Lewis structure for the molecule, assuming carbon always forms four
bonds in its stable compounds.
(4)
b) How many rr and a bonds are in the molecule?
(2)
c) What is the hybridization of atomic orbitals around the carbon atom associated with
the shortest bond in the molecule?
(2)
d) What is the bond angle around the carbon atom associated with the shortest bond in
the molecule?
(2)
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END OF QUESTION PAPER
General Chemistry 1B (GNC502S)
1'1 Opportunity November 2024
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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 mm Hg= 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 (GNCS02S)
1'1 Opportunity November 2024
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nAml BIA UnlVERSITY
OF SCIEnCE AnDTECHnOLOGY
FacultyofHealthN, atural
ResourceasndApplied
Sciences
13JacksonKaujeuaStreet T: +264612072012
Private Bag13388
F: +264612079012
Windhoek
E: dbcp@nust.na
NAMIBIA
W: www.nust.na
Schoolof NaturalandApplied
Sciences
Departmentof Biology,
ChemistryandPhysics
l1ydrQ<Jen
1
H
1.0079
Hlhlum
3
ber111ium
4
Li Be
6.941
sodium
11
Na
9.0122
magnesi.Jm
12
Mg
22.990
polJSSlllm
19
K
24.305
c.1lclum
20
Ca
scnndium
21
Sc
lilnni.Jrn
22
Ti
v~nJdium chromium manganese Iron
23
24
25
26
V Cr Mn Fe
W.098
rutldlum
37
Rb
40.078
slronlium
38
Sr
44.956
yllrium
39
y
47.867
zirconium
40
Zr
50.942
51.996
54.938
niobium niolybdenum laclmelium
41
42
43
Nb Mo Tc
55.845
rulhenium
44
Ru
85.468
c.1eslum
55
Cs
1?.2.91
francium
87
Fr
12231
87.62
bJrium
56
Ba
137.33
radium
88
Ra
12261
57-70
*
89-102
**
88.906
lulsllum
71
91.224
h.ifnlum
72
Lu Hf
174.97
178.49
IJwr&nclun rulMrforcflum
103
104
Lr Rf
12621
12611
92.906
l,inlnlum
73
Ta
180.95
dubnium
105
Db
12621
95.94
lungslen
w74
183.84
seJborglum
106
Sg
12661
1981
rll~nlum
75
Re
1B6.21
bohrium
107
Bh
12641
101.07
osmium
76
Os
190.23
hasslum
108
Hs
12691
boron
5
carbon
6
nllrcg&i
7
BCN
10.B11
aluminium
13
Al
12.011
sir.on
14
Si
14.007
phosphorus
15
p
CObJII
27
Co
nick~I
28
Ni
copper
zinc
29
30
Cu Zn
26.982
gn!llum
31
Ga
28.086
germ.,ni.Jm
32
Ge
30.974
msenlc
33
As
58.933
rhcxlium
45
Rh
58.693
pallJdium
46
Pd
63.546
sil1,•er
47
Ag
65.39
cadmium
48
Cd
69.723
n1dium
49
In
72.61
fin
50
Sn
74.922
::inlimony
51
Sb
102.91
,rcrum
77
Ir
105.42
plnlinum
78
Pt
107.87
(lOkJ
79
Au
112.41
mercury
80
Hg
114.82
lllnllklm
81
Tl
118.71
lead
82
Pb
121.76
blsmulh
83
Bi
192.22
195.08
196.97
200.59
mellnerium ununnillum ununun!um ununbitrn
109
110
111
112
Mt UunUuuUub
204.38
207.2
ununqu.ldium
114
Uuq
208.98
12681
12711
12721
12771
12891
oxygen
8
0
15.999
SUifur
s16
32.065
s~lenium
34
Se
78.96
lalurium
52
Te
127.60
Polonium
84
Po
12091
llu011ne
9
F
1B.998
Chlorine
17
Cl
35.453
bromine
35
Br
79.904
iooine
53
I
126.90
aslnllne
85
At
12101
helium
2
He
4.0026
n€0n
10
Ne
20.180
aroon
18
Ar
39.948
kryplon
36
Kr
83.BO
xenon
54
Xe
131.29
melon
86
Rn
12221
*Lanthanide series
**Actinide series
lonlhnnum
57
La
138.91
::iclinium
89
Ac
12271
c~rium
58
Ce
140.12
lhorium
90
Th
232.04
pr.lseodyrniurr neodymium promelhium
59
60
61
Pr Nd Pm
140.91
prolactinium
91
Pa
144.24
U'Onium
92
u
11451
neptunium
93
Np
231.04
238.03
12371
somJrlum europum
62
63
Sm Eu
15(•.36
plulonium
94
151.96
americium
95
Pu Am
12441
12431
g:idoinium
64
Gd
157.25
curium
96
Cm
12471
t~rbium d1•sprosium holmium
65
66
67
Tb Dy Ho
158.93
162.50
164.93
berkE;tlum cnifornium einsleinlt,n1
97
98
99
Bk Cf Es
12471
12511
12521
erblun
68
lhtilLrn
69
yllerbit1m
70
Er Tm Yb
167.26
168.93
173.04
fermium niendE;tevium nobE;tium
100
101
102
Fm Md No
12571
12581
12591