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GNC502S - GENERAL CHEMISTRY 1B -2ND OPP - JAN 2023 |
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nAm I BIA u n IVERS ITY
OF SCIEn CE Ano TECHn OLOGY
FACULTYOF HEALTH,NATURAL RESOURCESAND APPLIEDSCIENCES
DEPARTMENT OF NATURAL AND APPLIED SCIENCES
QUALIFICATION: BACHELOROF SCIENCE
QUALIFICATION CODE: 07BOSC
COURSE CODE: GNC502S
LEVEL: 5
COURSE NAME: GENERALCHEMISTRY 1B
SESSION: JANUARY 2023
PAPER:THEORY
DURATION: 3 HOURS
MARKS: 100
SUPPLEMENTARY/SECOND OPPORTUNITY EXAMINATION QUESTION PAPER
EXAMINER(S)
MODERATOR:
DR. EUODIA HESS
DR. MARIUS MUTORWA
DR. JULIEN LUSILAO
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
PERMISSABLE MATERIALS
Non-programmable calculators
ATTACHMENTS
1. List of useful constants
2. Periodic Table
THIS QUESTION PAPER CONSISTS OF 10 PAGES
(Including this front page, list of useful constants and Periodic Table)
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SECTIONA: MULTIPLECHOICEQUESTIONS
[60]
• There are 20 multiple choice questions in this section. Each question carries 3 marks. Answer
ALLquestions by selecting the letter of the correct answer.
• Choose the best possible answer for each question, even if you think there is another
possible answer that is not given.
1. Consider the exothermic combustion of coal. Which of the following could increase the rate
of reaction?
A. using smaller pieces of coal
B. increasing the concentration of oxygen
C. lowering the temperature
D. both (a) and (b) are correct
E. choices (a), (b) and (c) are all correct
2. Which of the following is/are expected to affect the rate of a chemical reaction?
A. Decreasing the reactant concentrations.
B. Increasing the available surface area of a reactant
C. Shaking a well mixed reaction solution.
D. A and B
E. C and A
3. For a certain overall third-order reaction with the general form aA products, the initial
rate of reaction is 0.50 M·s-1 when the initial concentration of the reactant is 0.32 M. What
is the rate constant for this reaction?
A. 0.02 M- 2,s-1
B. 15 M- 2-s-1
C. a.soM- 2-s-1
D. 0.20 M- 2,s-1
E. 47 M- 2-s-1
4. When 10.0 g KOH is dissolved in 100.0 g of water in a coffee-cup calorimeter, the
temperature rises from 25.18 °C to 47.53 °C. What is the enthalpy change per gram of KOH
dissolved in the water? Assume that the solution has a specific heat capacity of 4.18 J/g·K
A. -116 J/g
B. -934J/g
C. -1.03 X 103 J/g
D. -2.19 X 103 J/g
E. -1.03 X 104 J/g
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5. Which of the following statements is/are CORRECT?
A. If a reaction occurs at constant pressure, q = t:.H.
B. The change in energy for a system is defined as the sum of the energies transferred as
heat and work (i.e., t:.U = q + w).
C. If a reaction occurs at constant volume, q = w
D. A and B
E. A and C
6. The heat of vaporization of benzene, C5H5,is 30.7 kJ/mol at its boiling point of 80.1 °C. How
much energy in the form of heat is required to vaporize 102 g benzene at its boiling point?
A. 0.302 kJ
B. 23.6 kJ
C. 24.2 kJ
D. 40.1 kJ
E. 3.14 X 103 kJ
7. Which of the following statements is/are CORRECT?
A. Product concentrations appear in the numerator of an equilibrium constant expression
B. A reaction favors the formation of products if K » 1.
C. Stoichiometric coefficients are used as exponents in an equilibrium constant expression
D. A, Band C
E. A and B
F. C and A
8. What is the expression for Kcfor the following equilibrium?
CaSO3(s) CaO(s) + SO2(g)
A. [CaOJ[SO2]
B. [SO2]
C. [CaO][SO2] / [CaSO3]
D. [CaSO3]/ [CaO][SO2]
E. [CaO]
9. Given the following chemical equilibrium:
COCl2(g) CO(g) + Cli(g)
Calculate the value of Kc,given that Kp= 6.5 x 1011 at 298 K.
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A. 1.5 X 10-12
B. 3.8 X 10-ll
C. 1.1 X 109
D. 2.7 X 1010
E. 1.6 X 1013•
10. What is the reaction quotient, Q, for the equilibrium
CuCl{s);::::::c::u: +(aq) + cI-(aq)
When 0.3746 L of 4.356 x 10-4 M cu+ is combined with 0.4326 L of 8.17 X 10-4 M cI- in the
presence of an excess of CuCl{s)?
A. 9.46 X 10-8
B. 3.8 X 10-7
C. 6.18 X 10-8
D. 7.26 X 10-8
E. 2.46 X 10-7
11. Which of the following ground-state electron configurations corresponds to an atom having
the largest ionization energy?
A. [Ar]3d104s24p3
B. [Ne]3s 23p 3
C. [Ne]3s 23p 2
D. [Kr]4d105s25p3
E. [Xe]4f145d 1°6s26p3
12. The quantum numbers of an atom's highest-energy valence electrons are n = 5 and I= 1.
The element to which this atom belongs could be a:
A. inner transition metal.
B. alkali metal.
C. s-block main-group element.
D. transition metal.
E. p-block main-group element.
13. What is the total number of electrons in p orbitals in a ground-state vanadium atom?
A.6
B.18
C. 12
D.24
E.30
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14. Which Lewis dot formula for pyrophosphate, P2074-, minimizes formal charge?
A.
:o:
:o:
4- B.
:o:
:o:
4-
=.o. -p-1oI1-p-o....:
11
I
..
:·o•-p-oII-IIp-o..:..
II
I
..
:o:
:o:
:o:
:o:
C.
:o:
:o:
4-
:.o.-p-oII-p-o..:..
II
I
--
:o:
:o:
D.
:o:
:o:
4-
:o-p-o1-1p-o.:.
..
11 ..
11
11 ..
:o:
:o:
E.
:o:
:o:
4-
:Q-P-O-IIP-o:
..
..
I
I
:o:
:o:
15. The concept of resonance describes molecular structures that:
A. have several different geometric arrangements.
B. have delocalized bonding.
C. are formed from hybridized orbitals.
D. have different molecular formulas.
E. have electrons resonating.
16. Which of the following compounds would be expected to have the lowest melting point?
A. AIF3
B.RbF
C. NaF
D. MgF2
E. CaF2
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17. In which of the following species is there the greatest unequal sharing of the bonding
electrons?
A. 503
B. sol-
e. H2S
D. H20
E. NH4+
18. Rank the following species in order of decreasing radii: K+,c1·,Se2·, Br·.
A. Br· > Se2• > c1·> K+
B. se2· > Br· > c1·> K+
c. K+>c1-> se2• > Br·
D. Br·> c1-> Se2• > K+
E. c1-> Se2• > K+> Br·
19. According to the valence-bond theory, the bonding in ketene, H2CCO,is best described as:
A. five p bonds.
B. threes bonds and two p bonds.
C. fours bonds and two p bonds.
D. fours bonds and one p bond.
E. five s bonds.
20. What is the hybridization of I in IF4-7
A. sp3d
B.sp 3d2
C. sp2
D.sp
E.sp3
END OF SECTIONA
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SECTIONB:
[40)
There are FOURquestions in this section. Answer ALL questions.
Show clearly, where necessary, how you arrive at the answer as the working will carry marks too.
QUESTION 1
(10]
Calculate the standard enthalpy of formation of acetylene (C2H2)from its elements:
2 C (graphite)+ H2(g) C2H2(g)
a) C (graphite)+ 02 (g) CO2(g)
b) H2(g) + ½ 02 (g) H20 (I)
c) 2 C2H2(g) + 5 02 (g) 4 CO2(g) + 2 H20 (I)
b.H~xn = -393.5 kJ/mol
b.H~xn = -285.8 kJ/mol
b.H~xn = -2598.8 kJ/mol
QUESTION 2
The reaction of nitric oxide with hydrogen at 1280 °cis
NO (g) + H2 (g) N2 (g) + H20 (g)
The following data were collected at the above temperature:
Experiment
1
2
3
[NO] (M)
5.0 X 10-3
10.0 X 10-3
10.0 X 10-3
[H2] (M)
2.0 X 10-3
2.0 X 10-3
4.0 X 10-3
a) Determine the Rate law
b) Rate constant
c) Rate of reaction when [NO] = 12.0 x 10-3 M
(10]
Initial Rate (M/s)
1.3 X 10-S
5.0 X 10-5
10.0 X 10-5
QUESTION 3
(10]
The following compound is a synthetic intermediate in the production of lactacystin:
a) Identify the orbital hybridization of the atoms next to the two arrows.
(4)
b) Identify the molecular geometry of the atoms next to the two arrows.
(4)
c) Identify the bond angle around the atoms next to the two arrows.
(2)
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QUESTION 4
[10]
Methyl nitrate, CH3N03,is used a rocket propellant. One of the nitrogen-to-oxygen bond
length is 136 pm and the other two are 126 pm.
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 the
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 0-N-O bonds?
(1)
END OF EXAMINATION
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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
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PERIODIC TABLE OF THE ELEMENTS
-
18
1
2
H
1.00794 2
13
14
15
He
16
17 4.00260
34
5 6 7 8 9 10
Li Be
B C N 0 F Ne
6.941 9.01218
10.81 12.0ll 14.0067 15.9994 18.9984 20.179
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
II
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
"'O
DJ
OQ
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
(1)
I-'
Rb Sr y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
0
0
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
-+,
I-'
55 56 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
0
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 186207 190.2 192.22 195.08 196.967 200.59 204.383 207.2 208.908 (209) (210) (222)
87 88 103 104 105 106 107 108 109 110 111 112
114
116
118
Fr Ra Lr Rf Db Sg Bh Hs Mt Uun Uuu Uub
Uuq
(223) 226.02S (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
Actinides:
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)