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GNC502S - GENERAL CHEMISTRY 1B - 2ND OPP - JANUARY 2024 |
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n Am I B I A u nl VE Rs ITY
OF SCIEnCE AnDTECHnOLOGY
Facultyof Health,Natural
ResourceasndApplied
Sciences
Schoolof NaturalandApplied
Sciences
Departmentof Biology,
ChemistryandPhysics
13JacksonKaujeuaStreet T: +264612072012
PrivateBag13398
F: •264612079012
Windhoek
E: dbcp@nust.na
NAMIBIA
W: www.nust.na
QUALIFICATION: BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC
COURSE:GENERAL CHEMISTRY lB
DATE: JANUARY 2024
DURATION: 3 HOURS
LEVEL:S
COURSECODE: GNCS02S
SESSION: 1
MARKS: 100
SECOND 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 ANSWER SHEET.
1.1 The reduction of NO to N2with H2: 2NO (g) + 2H2 (g) N2 (g) + 2H2O (g), is found to have
the following experimentally determined rate equation: Rate= k[NO]2[H2]. What is the order
of the reaction with respect to NO?
A. 0
B. 1
C. 2
D. 3
1.2 If the concentration of NO is doubled and that of and H2 is constant, the rate of the
reaction would:
A. Decrease four fold
B. Increase four fold
C. Increase two fold
D. Decrease two fold
1.3 For the reaction:
2NaHCO3 (s) Na2CO3(s) + CO2 (g) + H2O (g)
Which one of the following is the correct expression for Kc?
A. Kc= [CO2][H2O]
B. Kc= [CO2]
C. Kc= [CO2][H2O][Na2CO3]/[NaHCO3]2
D. Kc= [CO2][Na2CO3]/[NaHCO3]2
1.4 The table below gives the initial concentrations and rate for three experiments. The
reaction is CO+ Cl2 COCh. What is the rate law for this reaction?
Experiment
1
2
3
[CO] (M)
0.30
0.10
0.30
[Cl2] (M)
0.10
0.30
0.30
Initial Rate of COCl2 (M min-1)
2.1 X 10-25
2.1 X 10-25
6.3 X 10-25
General Chemistry 1B (GNC502S)
2nd Opportunity January 2024
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A. Rate= k[CO][Clz]
B. Rate= k[CO]2[Clz]
C. Rate= k[CO]
D. Rate = k[CO][Cl2]2
1.5 For which of the following reactions does Kc= Kpat 25°C?
A. 2NH3(g) + CO2(g)::; N2CH4O(s)+ H2O(g)
B. 2N8r3(s)::; N2(g) + 3Br2(g)
C. 2KCIO3(s)::; 2KCl(s) + 3O2(g)
D. CuO(s) + H2(g) ::; Cu(/)+ H2O{g)
1.6 In the Copper Oxide (CuO) and Carbon Monoxide (CO) reaction, reducing agent is:
A. CuO
B. CO
C. Cu
D. CO2
1.7 In which of the following unbalanced reactions does chromium undergo oxidation?
A. Cr3+ Cr
B. cr3+ Cr2+
C. Cr3+ Cr2oi-
D. None of the above
1.8 The oxidation number of each chromium atom in Cr2O/- is:
A. +S
B. +6
C. +7
D. +12
1.9 The pH of a 1.25 x 10-3 M NaOH is:
A. 7.00
B. 2.90
C. 11.10
D. 10.90
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1.10 Which of the following describes the relationship between [H3O+] and [OH-]?
A. [H3O+][oH-] = 14.00
B. H3 0+] +[OH-]= 14.00
c. [H3O+][OH-1 = 1.0 x 10-14
D. [H3O+] +[OH-]= 1.0 X 10-14
1.11 Which compound has the highest boiling point?
a)
b)
CI H,-CH3
H3C-C-CH3
I
CH2CH3
c)
1.12 What is the correct IUPAC name for the compound shown below?
0
d)
A. 3-methyl-4-(1-methylethyl)-5-(propyl)-6-(dimethyl) octane
B. 4-(1,1-dimethylpropyl)-5-{1-methylethyl)-6-(methyl) nonane
C. 3-methyl-4-{1-methylethyl)-5-(1,1-dimethylpropyl) octane
D. 3-methyl-4-(1,1-dimethyl)-S-(l,l-dimethylpropyl)
nonane
1.13 Which one of the following compounds is an isomer of CH3CH2CH2CH2OH?
A.
0
B.
II
C. CH3CH2CHCH3
I
OH
D. Compounds Band C above
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1.14 What is the condensed formula of the compound below?
Br
Br
B. CH3CH2CH2(CH3)CH2CH(CH3)CHBr2
C. CH3CH2CH(CH3)CH(CH3)CH2CHBr2
D. None of the above structures are correct
1.15 How many isomers of C2H2Cl2 are polar?
A. 0
B. 1
C. 2
D. 3
1.16 What is the correct molecular geometry for SeBr3+?
A. trigonal pyramidal
B. tetrahedral
C. trigonal planar
D. T-shaped
1.17 PCl5 has _____
electron domains and a _____
A. 6 and trigonal bipyramidal
B. 6 and seesaw
C. 5 and square pyramidal
D. 5 and trigonal bipyramidal
molecular arrangement.
1.18 Which of the following statement(s) is/are correct in describing an orbital?
I. a region of high electron density.
II. a region in an atom where an electron is likely to be found.
Ill. a wave function resulting from specific values assigned to
quantum numbers in wave equations.
IV. a spherical region around a nucleus where an electron can be found.
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A. II only
8. I and II
C. I, II and Ill
D. I, II, Ill and IV
1.19 The statement that the first ionization energy for an oxygen atom is lower than the first
ionization energy for a nitrogen atom is:
A. Inconsistent with the general trend relating changes in ionization energy across a
period from left to right and due to the fact that oxygen has one doubly occupied 2p
orbital and nitrogen does not.
8. Consistent with the general trend relating changes in ionization energy across a
period from left to right because it is harder to take an electron from an oxygen
atom than from a nitrogen atom.
C. Consistent with the general trend relating changes in ionization energy across a
period from left to right because it is easier to take an electron from an oxygen atom
than from a nitrogen atom.
D. Inconsistent with the general trend relating changes in ionization energy across a
period from left to right and due to the fact that the oxygen atom has two doubly
occupied 2p orbitals and nitrogen has only one.
1.20 What species has the electron configuration [Ar]3d2?
A. Mn2+
8. cr2+
c. v3+
D. Fe3+
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)
(15)
2.1 Calculate the oxidation numbers ofthe underlined elements in the following compounds.
(5)
A. NO2
B. N2Os
C. .!::!.CIO3
D. .!::!.NO3
E. Ca(NO3}z
2.2 Write a balanced ionic equation to represent the oxidation of iodide ion (I-)by
permanganate ion (MnQ4-) in basic solution to yield molecular iodine (12)and
manganese (IV) oxide (MnO2).
(10)
QUESTION 3
[10]
Propanoic acid (CH3CH2COOH,which we simplify and HPr) is an organic acid whose salts are
used to retard mold growth in foods. What is the [H3o+] of 0.10 M HPr (Ka= 1.3x10-5)?
QUESTION 4
[15]
4.1 The lactic acid molecule, CH3CH(OH)COOH,gives sour milk its unpleasant, sour taste.
A. Draw the skeletal structure for the molecule, assuming carbon always forms four
bonds in its stable compounds.
(3)
B. How many rr and crare 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)
General Chemistry 1B (GNC502S)
2nd Opportunity January 2024
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D. What is the bond angle around the carbon atom associated with the shortest bond in
the molecule?
(1)
4.2 The line-bond structure shown below is the compound aspartame, an artificial
sweetener commonly used as a sugar substitute in foods and beverages.
A. What is the correct molecular formula for aspartame?
(2)
B. Identify the functional groups present in aspartame.
(5)
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END OF QUESTION PAPER
General Chemistry 18 (GNCS02S)
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USEFULCONSTANTS
Gas constant, R = 8.3145 J ·moI·1 · K·1 = 0.083145 dm3 ·bar· moI·1 · K·1 = 0.08206 L atm moI·1 ·K·1
1 Pa · m3 = 1 kPa.L = 1 N ·m = 1 J
1 atm = 101325 Pa= 760 mm Hg= 760 torr
Avogadro's Number, NA= 6.022 x 1023 moI·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}
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G)
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PERIODIC TABLE OF THE ELEMENTS
18
l
2
H
1.00794 2
13 14 IS
He
16 17 4.00260
34
56
7
8 9 lO
Li Be
B C N 0 F Ne
6.941 9.01218
10.81 12.01I 14.0067 15.9994 18.9984 20.l 79
11 12
13 14 15 16 17 18
Na Mg
Al Si p s Cl Ar
22.9898 24.305 3
4
5
6
7
8
9
10
11
12 26.9815 28.0855 30.9738 32.06 35.4S3 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 75 76 77 78 79 80 81 82 83 84 85 86
Cs Ba Lu Hf Ta w Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
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)
87 88 103 104 105 106 107 108 109 110 111 112
I 14
116
118
Fr Ra Lr Rf Db Sg Bh Hs Mt Uun Uuu Uub
Uuq
(223) 226.025 (260) (261) (262) (263) (264) '265) '268) (269) (272) (269)
Uuh
Uuo
Lanthanides: 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
Actlnlde.s:
89 90 91 92 93 94 95 96 97 98 99 100 101 102
Ac Th Pa u Np Pu Am Cm Bk Cf Es Fm Md No
227.028 232.038 231.036 238.029 237.048 (244) (243) (247) (247) (251) (252) (257) (258) (259)