EXAMINER(S) | DR. EUODIA HESS DR. JULIEN LUSILAO …
Transcript of EXAMINER(S) | DR. EUODIA HESS DR. JULIEN LUSILAO …
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NAMIBIA UNIVERSITY OF SCIENCE AND TECHNOLOGY
FACULTY OF HEALTH AND APPLIED SCIENCES
DEPARTMENT OF NATURAL AND APPLIED SCIENCES
QUALIFICATION: BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC LEVEL: 5
COURSE NAME: GENERAL CHEMISTRY 1B COURSE CODE: GNC502S
SESSION: NOVEMBER 2019 PAPER: THEORY
DURATION: 3 HOURS MARKS: 100
FIRST OPPORTUNITY EXAMINATION QUESTION PAPER
EXAMINER(S) | DR. EUODIA HESS
DR. MARIUS MUTORWA
MODERATOR: | DR. JULIEN LUSILAO
INSTRUCTIONS
Answer ALL the questions.
Write clearly and neatly.
Number the answers clearly
All written work must be done in blue or black ink and sketches can be done in pencil
PON b
P
5. No books, notes and other additional aids are allowed
THIS QUESTION PAPER CONSISTS OF 12 PAGES (Including this front page and attachments)
Page 1 of 12
SECTION A
QUESTION 1: Multiple Choice Questions
[50]
[50] There are 25 multiple choice questions in this section. Each question carries
2 marks.
Answer ALL questions 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.
Which of the following is true regarding the relative molar rates of disappearance of the reactants and the appearance of the products?
2NO (g) + 2H2 (g) > No (g) + 2H20 (g)
I. Nz appears at the same rate that H2 disappears.
Il. H2O appears at the same rate that NO disappears.
lll. NO disappears at the same rate that H> disappears.
A. lonly
B. land Il only
C. land Ill only
D. Il and Ill only
E. LI, and lll
For the reaction 2A + B > C, experimental data were collected for three trials:
Experiment | [A] (M) [B] (M) Initial Rate Appearance of C (M sec?)
1 0.40 0.20 5.5x 10°
2 0.80 0.20 5.5x 10°
3 0.40 0.40 2.2 x 107
What is the rate law of the reaction?
A. Rate = k[A][B]
B. Rate = k[A]°[B]?
C. Rate = k[A]2[B]?
D. Rate = k[A]?[B]°
E. Rate = k[A][B]?
Page 2 of 12
3. For areaction A + B > C+D, the energy of activation and enthalpy change of reaction were found to be 80 kJ mol and + 20 kJ mol, respectively. What is the value of the activation energy for the reverse reaction?
A. + 60 kJ mol?
B. + 100 kJ mol?
C.—80 kJ mol
D. + 20 kJ mol
E. Insufficient information
4. Write the appropriate equilibrium constant expression, Kc, for the following reaction:
2CO(g) + O2(g) 2CO2(g)
A. Ke =k[CO]*[O2]
[co, ] PKs = Feofo,]
[coP [o,] “Teo, |
_ {co,f *~ |cofo,]
__[co,P [coP’[o, ]
c
5. Suppose we rewrite the balanced reaction in Question 4 as:
CO(g) + % O2(g) CO2(g)
What would be the equilibrium constant, K, for this reaction?
A. Same(i.e. Ke” = Ke)
B. Ke’ = (Ke)”
C. Ke =K-/2
D. Ke’ = Ke2
E. Ke =1/K
6. If Keq is small, it indicates that equilibrium occurs:
At a low product concentration
At a high product concentration
After considerable time
With the help of a catalyst
mo
fo 8S >
With no forward reaction
Page 3 of 12
Vs
10.
For which one of the following equilibrium equations will Kp be equal to K.?
A. PCls(g) S PCl3(g) + Cla(g)
B. COCl2(g) S CO(g) + Clo(g)
C. H2(g) + la(g) S 2HI(g)
D. 3H2(g) + No(g) S 2NHa(g)
E. 2S03(g) 2SO2(g) + O(g)
Consider the following equilibrium:
H2(g) + lo(g) S 2HI(g)
At equilibrium [H2] = 0.00220 M, [lz] = 0.00220 M, and [HI] = 0.0156 M. The value of the Ke is
A. 3.10 x 10%
B. 1.99 x10?
C. 5.03 x 10!
D. 3.22 x 10°
E. 1
Arrhenius would define a base as:
I. Something which yields hydroxide ions in solution
ll. A proton acceptor
Ill. An electron pair donor
A. 1, Il, and Ill
B. land Ill
C. Ilonly
D. lonly
E. land Ill
In the equilibrium expression for the reaction BaSOa(s) Ba?*(aq) + SO7 (aq), Ksp is equal
to:
[Ba** ][SO77]
, [Baso, |
B. [BaSO, ]
[Ba** ][SO7]
Page 4 of 12
C. [Ba**][SO7
[Ba** [SOF] BaSO,
E. None of the above
11. Calculate the concentration (mol/L) of a solution of Ba(OH)2 that has a pH of 12.7?
12.
13.
A. 1.0x 1073
B. 5.0x 10?
C. 2.0x10¥
D. 2.5x 10?
E. 1.27x10!
A buffer solution was prepared by mixing 100 mL of a 1.2 M NH3 solution and 400 mL of a 0.5
M NH4CI solution. What is the pH of this buffer solution, assuming a final volume of 500 mL
and Kp= 1.8 x 10°?
What kind of hybridization do you expect for each of the carbon atoms indicated in 2- methylpropene?
— 24g |
p>
O
Q-O
Ais sp?; Bis sp; Cis sp
Ais sp?; B is sp?; Cis sp?
A is sp’; B is sp; Cis sp?
9 9 F >
Ais sp; B is sp?, Cis sp?
E. Ais sp?; Bis sp; Cis sp?
Page 5 of 12
14. The structure below is that of Capsaicin, the pungent substance in chilli peppers.
O
2 N ao | H
HO
The functional groups of the above structure include:
amide; ester; alcohol; alkene
ether; amide, alkyne; alcohol
alcohol; ester; ether; amine
ester; carboxylic acid; alkene; alcohol
mofo
f >
amine; ester; alkene; alcohol
15. What is the correct IUPAC name for the compound shown below?
3-methyl-4-(1-methylethyl)-5-(propyl)-6-(dimethyl) octane
4-isopropyl-3-methyl-tert-pentylnonane
4-(1, 1-dimethylpropyl)-5-(1-methylethyl)-6-(methyl) nonane
3-methyl-4-(1-methylethyl)-5-(1,1-dimethylpropyl) nonane
mono
8 >
3-methyl-4-(1,1-dimethyl)-5-(1,1-dimethylpropyl) nonane
16. The line-bond structure shown below is the compound Folic Acid, an essential vitamin that the body uses to make DNA and metabolise amino acids.
HoN N N
N Zz NH a N O
OH NH OH
Zz O OH
Page 6 of 12
The correct molecular (or condensed) formula for Folic Acid is:
A. CigHi9N7Oq
B. Ci9H7N7O¢
C. CisHi3N7Oc¢
D. CigHigN7O¢
E. C1i9H33N70¢
17. Which one of the structures in a to d is NOT a valid resonance structure for the anion in the
box below?
O:
EH 3
O: : :O:
a. Hie Kon, b. Hoo SoH, c. Hee by d. yc cH 3 3
moO WB >
oo
noaoa»o
w
18. How are the molecules in the following pair related?
i -OH and
H3C~ ~CHg HS NH
They are constitutional isomers
They are stereoisomers
They are resonance structures
Conformational isomers
moo
7 >
They are unrelated
Page 7 of 12
19. Which of the following molecules contain both covalent and ionic bonds?
CH30H NaoCO3 NHyCl NaCl I Il Il IV
A. land Il
B. land IV
C. I, land Iv
D. Iland Ill
E. Il, land IV
20. Which of the molecules below are polar?
O I
EpC=CH, Cw H CHCbh H3;C—CH3; CH;0H
I I II IV Vv
A. Ill, Vand V
B. land IV
C. Il, land V
D. land Ill
E. 1, ll, land V
21. What is the electron configuration for the Fe3+ ion?
A. [Ar]4s13d6
B. [Ar]4s93q7
C. [Ar]4s03d5
D. [Ar]4s23d9
E. [Ne]3s23p10
Page 8 of 12
22. Using the VSEPR model, the molecular geometry of the central atom in tetrafluoroborate
22%
24.
25.
ion is
A. trigonal planar
B. square pyramidal
C. square planar
D. trigonal bipyramidal
E. octahedral
The electron domain and molecular geometry of BrO?- is
A. tetrahedral and trigonal planar
B. tetrahedral and bent
C. trigonal planar and trigonal planar
D. trigonal pyramidal and linear
E. trigonal pyramidal and seesaw
The hybridizations of bromine in BrFs and of arsenic in AsFs are and
, respectively.
A. sp3d2, sp3d
B. sp3, sp3d
C. sp3d, sp2d2
D. sp3d, sp3
E. sp3d2, sp>d2
A valid Lewis structure of
A. POa>
B. SeF4
C. CF4
D. SiFa
E. NF3
cannot be drawn without violating the octet rule.
END OF SECTION A
Page 9 of 12
SECTION B: [50]
QUESTION 1 [3]
Considering the following reaction: 2SO3 (g) 2SQz (g) + O2 (g) AH® = +197 kJ What will happen to the number of moles (increase, decrease or remain the same) of SO3 in equilibrium with SO2 and Oz in each of the following cases?
a. Oxygen gas is added. (2)
b. The pressure is increased by decreasing the volume of the reaction container. (2)
c. The temperature is decreased. (2)
d. Gaseous sulphur dioxide is removed. (2)
QUESTION 2 [10]
2.1 In a NaOH solution, [OH] is 2.9 x 10 M. Calculate the pH of the solution. (2)
2.2 Calculate the pH of a:
a. 1.0 x 10° M HCl solution (4)
b. 0.020 M Ba(OH)2 solution (4)
QUESTION 3 [7] 3.1 Balance the following half reactions:
a. CrO4~ (aq) > Cr(OH)s(s) (in basic medium) (3)
b. HNO2 (aq) > NH@ (aq) (in acidic medium) (3)
3.2 Find the oxidation number of Cr in K2Cr207 (1)
QUESTION 4 [12]
A molecular compound is composed of 60.4% Xe, 22.1% O and 17.5% F, by mass. If the molecular weight is 217.3 amu:
4.1 What is the molecular formula? (5)
4.2 Draw the most dominant Lewis structure of the compound? (3)
4.3 Predict the molecular geometry using VSEPR model. (2)
4.4 Describe the bonding using valence bond theory. (2)
Page 10 of 12
QUESTION 5
5.1 Arrange the bonds in each of the following sets in order of increasing bond polarity.
a. C-F; O-F and Be-F
b. O-Cl; S-Br and C-P
5.2 Draw all possible resonance structures of the following molecules.
a. SeQ2
b. C204
QUESTION 6
6.1 The molecule AsF3 has a dipole moment of 2.59D. Which of the geometries are possible: trigonal planar, trigonal pyramidal or T-Shaped? Explain your choice of answer.
6.2 What is the formal charge of the central atom in the SiF,2" ion?
THE END
GOODLUCK
[8]
(4)
(4)
[5]
(3)
(2)
USEFUL CONSTANTS:
Gas constant, R = 8.3145 J-mol?: kK? = 0.083145 dm?: bar: mol: K2
= 0.08206 L atm mol?: K2
1Pa:m?=1kPa.l =1N-m =1)J
1 atm = 101 325 Pa = 760 mmHg = 760 torr
Avogadro’s Number, Na = 6.022 x 1023 mol?
Planck’s constant, h = 6.626 x 1034 Js
Speed of light, c = 2.998 x 108 ms?
Page 11 of 12
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