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GNC502S - GENERAL CHEMISTRY 1B - 1ST OPP - NOVEMBER 2023 |
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nAmlBIA UnlVERSITY
OF SCIEnCEAnDTECHnOLOGY
Facultyof Health,Natural
ResourceasndApplied
Sciences
Schoolof Natural andApplied
Sciences
Departmenot f Biology,
ChemistryandPhysics
13Jackson Kaujeua Street
Private Bag 13388
Windhoek
NAMIBIA
T: •264 612072012
F: •264 612079012
E: dbcp@nust.na
W: www.nust.na
QUALIFICATION: BACHELOR OF SCIENCE
QUALIFICATIONCODE: 07BOSC
COURSE:GENERAL CHEMISTRY lB
DATE: NOVEMBER 2023
DURATION: 3 HOURS
LEVEL:5
COURSECODE: GNC502S
SESSION: 1
MARKS: 100
FIRST OPPORTUNITY: QUESTION PAPER
EXAMINER: DR MARIUS MUTORWA
MODERATOR: DR MPINGANA AKAWA
INSTRUCTIONS
1. Answer all questions on the separate answer sheet.
2. Please write neatly and legibly.
3. Do not use the left side margin of the exam paper. This must be allowed for the
examiner.
4. No books, notes and other additional aids are allowed.
5. Mark all answers clearly with their respective question numbers.
PERMISSIBLE MATERIALS:
1. Non-Programmable Calculator
ATTACHEMENTS
1. Useful Constants
2. Periodic Table
This paper consists of 10 pages including this front page
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SECTION A
(60 MARKS)
QUESTION 1: MULTIPLE CHOICE QUESTIONS
[60)
Evaluate the statements in each numbered section and select the most appropriate answer
or phrase from the given possibilities. Fill in the appropriate letter next to the number of the
correct statement/phrase on your ANSWERSHEET.
1.1 Which statement concerning relative rates of reaction is correct for this chemical
equation given below?
2 CH3OH(g) + 3 O2(g) 2 CO2(g) + 4 H2O(g)
A. The rate of disappearance of CH3OH is equal to the rate of disappearance of 02.
B. The rate of disappearance of CH3OHis two times the rate of appearance of H2O.
C. The rate of disappearance of CH3OH is half the rate of appearance of CO2.
D. The rate of appearance of H2O is two times the rate of appearance of CO2
1.2 Which relationship correctly compares the rates of the following reactants and products?
2 NOCl(g) 2 NO(g) + Clz(g)
l\\.[NOCl] l\\.[NOJ .6.C[l2]
A.
ill
= ill + ill
B. ll.[NOCl]
ill
l\\.[NOJ
ill
ll.[ Cl2]
ill
1 t.[NOCI] 1 l!.[NOJ t.[Ci2]
C. 2 bi =2--st=~
D. -2.6.[NOCIJ 2Ll[NOJ .6.[CI2)
Lit
= Lit =
1.3 What is the name given to a substance that increases the rate of a chemical reaction but
is not itself consumed?
A. Reactant
B. Intermediate
C. Enthalpy
D. Catalyst
1.4 Write the appropriate equilibrium constant expression Kcfor the following reaction:
General Chemistry 1B (GNC502S)
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A. Kc= k[CO]i[O2]
B. Kc= [CO2]/ [CO] [02]
C. Kc= [CO2]2/ [CO]2 (02]
D. Kc= [CO]2 [02] / [CO2]
1.5 Write the expression for Kfor the reaction of hydrofluoric acid with water.
[F-]
B. K=--
[HF]
1.6 What is the balanced equation for the following equilibrium expression?
A. 2 S02(g) + 02(g) -=-----2--S"°03(g)
B. 2 S03(g) -=-----2--S"°02(g) + 02(g)
C. 2 S03(oq) -=-----2--S"0' 2(oq) + 02(oq)
D. 2 S02(oq) + 02(oq)
2 S03(oq)
1.7 Which of these physical changes would require the addition of energy?
A. melting a solid
B. condensing a gas
C. freezing a liquid
D. All of the above
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1.8 Which of the following is an endothermic process?
A. work is done by the system on the surroundings
B. heat energy flows from the system to the surroundings
C. work is done on the system by the surroundings
D. heat energy is evolved by the system
1.9 Specific heat capacity is the:
A. capacity of a substance to gain or lose a 1.00 J of energy in the form of heat.
B. quantity of heat needed to change the temperature of 1.00 g of a substance by 4.184
K.
C. quantity of heat needed to change the temperature of 1.00 g of a substance by 1 K
D. temperature change undergone when 1.00 g of a substance absorbs 4.184 J.
1.10 Exactly 253.0 J will raise the temperature of 10.0 g of a metal from 25.0 °C to 60.0 °C.
What is the specific heat capacity of the metal?
A. 12.2 J/(g·°C)
B. 1.38 J/(g·°C)
C. 0.723 J/(g•0 C)
D. 60.5 J/(g•0 C)
1.11 In ionic bond formation, the lattice energy of ions ____
ion charges ___
and the radii ____
_
as the magnitude of the
A. Increases, decrease, increase
B. Increase~ increase, increase
C. Decreases, increase, increase
D. Increases, increase, decrease
1.12 There are _____
A. 18
B. 20
C. 26
D. 32
valence electrons in the Lewis structure of CH3OCH2CH3.
1.13 A valid Lewis structure of _____
A. PQ43-
B. SiF4
C. CF4
D. SeF4
cannot be drawn without violating the octet rule.
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1.14 CIF3has a T-Shaped geometry. How many non-bonding domains does the molecule
have?
A. 1
B. 2
C. 3
D. 4
1.15 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£O,BeH2
C. ~Cl3, HNO
D. NH3, HNO
1.16 Find the correct stereochemistry for the following four alkenes:
A
B
C
D
A. A is Z, B is Z, C is £, D is £
B. A is Z, B is £, C is Z, D is f
C. A is £, B is f, C is ~' D is Z
D. A is Z, B is Z, C is £, D is Z
1.17 Using the VSEPRmodel, the molecular geometry of the central atom in
tetrafluoroborate ion is -----
A. square planar
B. trigonal planar
C. square pyramidal
D. trigonal bipyramidal
General Chemistry 18 (GNC502S)
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1.18 The hybridizations of bromine in BrF5 and of arsenic in AsF5 are _____
and
respectively.
A. sp3,sp3d
8. sp3d, sp3d2
C. sp3d2, sp3d
D. sp3d2, sp3d2
1.19 Which is NOT a valid resonance structure for the anion in the box below?
1.20 Which of the following is the constitutional isomer of 4-isopropyloctane?
A. 3-ethyl-2,4,5-trimethyloctane
8. isobutylcyclohexane
C. 4-ethyl-2,2-dimethylheptane
D. 4-ethyl-2,2-dimethyloctane
END OF SECTION A
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SECTION B: SHORT/LONG ANSWER QUESTIONS
Please answer ALL of the questions in this section.
QUESTION 2
(40 MARKS)
[10)
2.1 A 466 g sample of water is heated from 8.50 °C to 74.60 °C. Calculate the amount of
heat absorbed (in kJ) by water.
(4)
2.2 Calculate the standard enthalpy change for the reaction:
(6)
Given that:
a) 2 Al (s) + 3/2 02 (g)
b) 2 Fe (s) + 3/2 02 (g)
A/203 (s) [j,H,xn°= -1 669.8 kJ/mo/
Fe203(s) /j,H,xn°= - 882.2 kl/mot
QUESTION 3
3.1 In a NaOH solution [OH-] is 2.9 x 10-4M. Calculate the pH of the solution.
3.2 Calculate the pH of a: .
a) 1.0 x 10-3 M HCI solution
b) 0.020 M Ba(OH}i solution
QUESTION 4
4.1 Convert the following condensed formula to a skeletal structure.
[10)
(3)
(3)
(4)
[12)
(2)
4.2 What is the IUPAC name of the compound below?
(3)
4.3 Enalapril is currently in clinical trials for congestive heart failure, and its structure is given
below.
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Enalapril
a) What is the correct molecular formula for this interesting antihypertensive agent?
(2)
b) Identify the functional groups present in Enalapril.
(5)
QUESTION 5
[8]
The orbital diagram below shows the valence electrons for a 2+ ion of an element.
4d
5.1 What is the ion?
(2)
5.2 What is the noble gas electronic configuration of the natural element?
(2)
5.3 Chloric acid is a weak acid with the formula HCIO3. Draw the resonance structures of
HCIO3,and clearly indicate which of the structure is the most stable showing the lone pairs
of electrons.
(4)
-------·----------------------------------·----------------------------------------------------------------------------------
END OF QUESTION PAPER
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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 = 1J
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
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G)
(t)
::J
(-t,)
Q)
n::r
I
(t)
3
V,
r-l,
-<
H
1.00794 2
34
I-'
OJ
Li Be
PERIODIC TABLE OF THE ELEMENTS
18
2
13
14
15
He
16
17 4.00260
56
7
8
9
IO
B C N 0 F Ne
G)
nz
6.941 9.01218
11 12
10.81 l 2.0 l l 14.0067 15.9994 18.9984 20.179
13 14 15 16 17 18
lJ1
0
Na Mg
Al Si p s Cl Ar
N
22.9898 24.305 3
4
5
6
7
8
9
10
11
12 26.9815 28.0855 30.9738 32.06 35.453 39.948
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
39.0983 40.08 44.9559 47.88 50.9415 51.996 54.9380 55.847 58.9332 58.69 63.546 6538 69.72 72.59 74.9216 78.96 79.904 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
85.4678 87.62 88.9059 91.22 92.9064 95.94 (98) 101.07 102.906 106.42 107.868 112.41 114.82 118.69 121.75 127.6 126.9 131.29
55 56 71 72 73 74 15 76 77 78 79 80 81 82 83 84 85 86
I-'
Cs Ba Lu Hf Ta w Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
0
132.905 137.33 174.967 178.49 180.948 183.85 186107 190.2 192.22 195.08 196.967 200.59 204383 207.2 208.908 (209) (210) (222)
"O
"O
87 88 I03 104 105 106 107 108 109 110 111 112
114
116
118
0
;::i.
Fr Ra Lr Rf Db Sg Bh Hs Mt Uun Uuu Uub
Uuq
Uuh
Uuo
C
::J
(223) 226.025 (260) (261) (262) (263) (264) (265) (268) (269) (272) (269)
;:;:
-<
z
0<
(t)
3
C'"
(-t,)
Lantbanides: 57 58 59 60 61 62 63 64 65 66 67 68 69 70
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb
138.906 140.12 140.908 144.24 (145) 150.36 151.96 157.25 158.925 162.50 161.930 167.26 166.934 173.04
N
0
Nw
Actinides:
89 90 91 92 93 94 95 96 97 98 99 IOO 101 102
Ac Th Pa u Np Pu Am Cm Bk Cf Es Fm Md No
I-'
227.028 232.038 231.036 238.029 237.048 (244) (243) (247) (247) (25 I) (252) (257) (258) (259)
0