iA)NAMIBIA UNIVERSITYOF 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 CODE: GNC502S COURSE NAME: GENERAL CHEMISTRY 1B

SESSION: NOVEMBER 2018 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

AnswerALL the questions.

Write clearly and neatly.

Numberthe answersclearly

ee

All written work must be donein blue or black ink and sketches can

be donein pencil

5. No books, notes and other additional aids are allowed

THIS QUESTION PAPER CONSISTS OF 11 PAGES(Including this front page and attachments)

SECTION A [50]

QUESTION1: Multiple Choice Questions [50]

There are 25 multiple choice questions in this section. Each question carries

2 marks.

AnswerALL questions by selecting the letter of the correct answer.

Choosethe best possible answerfor each question, evenif you think thereis

anotherpossible answerthatis not given.

Whatare the products formed during the following reaction: NaOH + HCl

A. Na(OH)2 + H2

B. NaCl +H2

C. NaCl +H20

D. NaCl +H2+ O02

Phosphoric acid has the formula

A. H2PO3

B. H2PQ4

C. H3POq4

D. H3PQ3

Which of the following could be addedto a solution of sodium acetate

(CH3COONa) to producea buffer?

A. Potassium acetate

B. Sodium chloride

C. Acetic acid

D . None of the above

In areaction between CuSOu,(s) and Zn(s),

A. Zinc experiences an increase in oxidation state

B. Cu undergoesoxidation

C. Zn undergoes reduction

D . Allofthe above

Page 2 of 11

5. Ascorbic acid (C6HgO¢) is a commonantioxidant that protects our bodies against radicals. In

the redox equation below that occurs in our stomach, which of the following pairs identifies

the reducing and oxidizing agents, respectively?99

9>

CeHsO¢ + H* + 2NOZ — CeHeOc¢ + 2H20 + 2NO

CeHs06 & NOZ

H* & NOZ

CeHsO6 & H*

H* & NOZ

6. Which of the following half reactions are balanced?

A.

B

G

D

ClO + H20 + e& = Cl2 + 20H

2 ClO’ + H20 + 2e => Cl2 + 30H”

2 ClO’ + 2 H20 + 2e° > Cl2 + 40H”

. ClO’ +H20 +e => Clo + 20H

7. Inthe rate law, Rate = k[NO]?[O2], the reactionis order with respect to

NO,

09

@>

order with respect to O2, and order overall.

first; second; third

second; zero; third

second;first; third

first; third; first

8. The table belowgivestheinitial concentrations and rate for three experiments.

Experiment [CO] (M) [Cl2] (M) Initial Rate of COCl2 (M min‘)

1 0.30 0.10 2.1 x 105

2 0.10 0.30 2.1 x 105

3 0.30 0.30 6.3 x 105

The reaction is CO + Cl2 > COCl2 . Whatis the rate law forthis reaction?

A. Rate = k[CO]

B. Rate = k[CO]?[Cl2]

C. Rate = k[COJ[Cl2]

D. Rate = k[CO][Cl2]*

Page 3 of 11

9,

10.

11.

12.

The reaction of elemental chlorine with ozoneoccurs by the two-step process shownbelow:

I. Cl+ O03 > CIO + O2

ll. lO+O > Cl+O2

Whichof the statements below is true regarding this process?

A. Clis a catalyst

B. O3 is a catalyst

C. ClO is a catalyst

D. O2 is an intermediate

For the reaction:

2NaHCOs(s) S NazCOs3(s) + CO2 (g) + H20 (g)

Which one ofthe followingis the correct expression for Ke?

A. Ke = [CO2]

B. Ke = [CO2][H20]

C. Ke = [CO2][H20][Na2CO3]/[NaHCO3]2

D. Ke = [CO2][NazCO3]/[NaHCO3]2

For which ofthe following reactions does K;. = Kp at 25°C?

A. 2NH3(g) + CO2(g) + N2CH4O(s) + H20(g)

B. 2NBra(s) No(g) + 3Br2(g)

C. 2KCIO3(s) S 2KCI(s) + 302(g)

D. CuO(s) + Ha(g) Cu(/) + H20(g)

Whichof the following electron configurations represents an excited state of the indicated

atom?

A. Ne: 1s? 2s? 2p®

B. N: 1s? 2s? 2p?

C. P: 1s? 2s? 2p® 3s* 3p? 4s*

D. Na: 1s? 2s? 2p® 3s? 3p? 3s?

Page 4of11

13. Which of the following statementsis true concerning the electron configuration [Ne]3s?3p+?

14.

15.

16.

99

@> It may represent a ground-state electron configuration of a Al* cation.

It may represent an excited-state electron configuration of a Mg atom.

It may represent an excited-state electron configuration of a Ne- anion.

It may represent a ground-state electron configuration of a Mg* cation.

Whichof the following statementsis true?

The krypton1s orbital is smaller than the helium 1s orbital because krypton's nuclear

charge drawstheelectronscloser.

The krypton1s orbital is smaller than the helium 1s orbital because krypton's p and d

orbitals crowdthes orbitals.

The krypton1s orbital and the helium 1s orbital are the same size because both s

orbitals can have only twoelectrons.

The krypton1s orbital is larger than the helium 1s orbital because krypton's ionization

energy is lowersoit's easier to removeelectrons.

In which pair do both compoundsexhibit predominantly ionic bonding?

09

7> RbCl and CaO

PCls and HF

Kl and O3

Na2SO3 and BH3

Whenthecations Na*, K*, Rb*, Cs* are combinedwith chloride ion in the gas phase to form

ion pairs, which pair formation releases the greatest amountof energy?

99

@> KCl

All release the same amountof energy.

RbCl

NaCl

Page 5 of 11

17. Which of the following statements concerning lattice energy is false?

18.

19.

20.

MgOhasa largerlattice energy than NaF.

B. The lattice energy for a solid with 2+ and 2—ions should be twotimesthat fora solid

with 1+ and 1—ions.

MgOhasa larger lattice energy thanLiF.

Lattice energy is often defined as the changein energy that occurs whenanionicsolid is

separatedinto isolated ions in the gas phase.

Whichof the following compounds would be expected to have the lowest melting point?

990

@> AIF3

RbF

NaF

MegF2

Whichof the following concerning electronegativity is/are correct?

1.

99

2>

Differences in element electronegativities may be used to predict the type of bonding,

ionic or covalent, in a substance.

Thelarger the differences in electronegativity between two bonded atoms the more

polar the bond.

The electrons in a polar bond tend to spend more time around the least electronegative

element.

1 only

2 only

3 only

1and 2

Which oneof the following has a Lewis formula mostsimilar to that of NO~?

99

®> O2

O27"

O2-

NO*

Page 6 of 11

21. Whatis the total numberof valence electrons in the monohydrogen phosphateion?

30

28

32

3499

Pp>

22. Which molecule or ion has the same molecular geometryfor its central atom as the

carbonateion?

H2CO

AsCl3

PF3

BrO3-99

»>

23. For which of the following moleculesor ions do the electron pairs on the central nitrogen

atom havea tetrahedral arrangement?

FNO

NF2-

N2F2

NO99

@>

24. What hybrid orbitals of sulfur are involved in the bondingin sulfur trioxide?

A. sp?

B. sp?d

C. sp?

D. spd?

25. Which of the following concerning nm and o bondsis/are correct?

1. Sigma bonds mayonly be formed from unhybridized orbitals.

2. Pibonds are formed from unhybridized p orbitals.

3. Api bond hasan electron distribution above and below the bond axis.

Page 7 of 11

1 only

2 only

1 and 2

2 and 390

@>

End of Section A

SECTION B:

QUESTION 1

1.1 Calculate the oxidation numbers of the elementsin the following compounds:

a) NO2

b) N20s

c) HCIO3

d) HNO3

e) Ca(NO3)2

1.2. Write a balanced ionic equation to represent the oxidation of iodideion (I") by

permanganate ion (MnOa)in basic solution to yield molecular iodine (lz) and

manganese(IV) oxide (MnOz2).

QUESTION 2

2.1 In a NaOHsolution [OH’] is 2.9 x 10M.Calculate the pH ofthe solution.

2.2 Calculate the pH of a

a) 1.0 x 10? M HCIsolution

b) 0.020 M Ba(OH)2solution

QUESTION 3

3.1 Identify and namethe following functional group in each of the following compounds.

a) CH3COCH3

b) CH30CH2CH3

c) CH3CH=CH2

d) CH3CH2COOH

e) CH3CH2CHO

Page 8 of 11

[50]

[15]

(5)

(10)

[10]

(2)

(4)(4)

[15]

(1)(1)(1)(1)(1)

3.2 Give the nameor condensedstructural formula for the following hydrocarbons.

a) CH,CHCH;

CHCH7CH»CH»CH3

CH,

b) 2,2-dimethylpentane

c) 4-ethyl-1,1-dimethylcyclohexane

d) (CH3)2CHCH2CH2C(CHs3)3

e) CH3CH2CH(C2Hs)CH2CH2CH2CH3

QUESTION 4

The lactic acid molecule, CH3CH(OH)COOH,gives sour milk its unpleasant, sour taste.

a) Draw the Lewis structure for the molecule, assuming carbon always forms four bonds

in its stable compounds.

b) How many m and o are in the molecule?

c) What is the hybridization of atomic orbitals around the carbon atom associated with

the shortest bondin the molecule?

d) What is the bond angle around the carbon atom associated with the shortest bond in

the molecule?

QUESTION 5

5.1 Write balanced nuclear equationsfor the following processes.

a) Ru-90 undergoesbeta emission

b) Se-72 undergoeselectron capture

c) Kr-76 undergoespositron emission

5.2 Whyis it important that radioisotopes used as diagnostic tools in nuclear medicine produce

gammaradiation when they decay?

THE END

GOODLUCK

(2)

(2)(2)(2)(2)

[5]

(2)(1)

(1)

(1)

[5]

(1)(1)(1)

(2)

Page 9 of 11

USEFUL CONSTANTS:

Gasconstant, R = 8.3145 J- mol: K+

= 0.083145 dm?: bar: mol?: K?= 0.08206 L atm mol: K+

1Pa*‘m?=1kPal =1N°m =13J

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 104 Js

Speedoflight, c = 2.998 x 108 ms?

Page 10 of 11

Page 11 of 11

1

1 H1.00794

2

3 Li 6.94

1

4 Be

9.01218

11 Na

22.9

898

12 Mg

24.305

3

PERIODICTABLEOFTHEELEMENTS

56

79

101]

12

1314

1516

17

18

2 He

4.00260

5 B 10.81

6 C12.011

7 N14

.006

7

8 oO

9 F15

.999

4/18

.998

4

10 Ne

20.179

13 Al26.9815

14 Si28

.085

5

15 P30.9738

16 S32.06

17 Cl 35.453

18 Ar

39.9

48

19 K39

.098

3

20

Ca

40.08

2122

Sc

T44.9559

4788

Z3 Vv50.9415

24

Cr

51.996

25

Mn

54.9

380

26

Fe

55.847

27

Co.

58.9332

28 Ni 58.69

29

Cu

63.546

30 Zn

65.38

3] Ga

69.7

2

32

Ge

72.5

9

33

AS

74.9

216

34 Se

78.9

6

35 Br

79.904

36 Kr

83.8

37 Rb

85.4

678

38 Sr

87.6

2

3940

YZr

88.9059

91.22

4] Nb

92.9064

42

Mo

95.9

4

43 Te

(98)

44

Ru

101.

07

45 Rh

102.906

46

Pd

106.

42

47 Ag

107.868

48

Cd

112.

41

49

In

114.82

50 Sn

118.

69

51 Sb

121.75

52 Te

127.

6

a3 I1269

54

Xe

131.29

55 Cs

132.

905

56

Ba

137.33

7172

Lu

Hf

174.967

178.49

73 Ta

180.

948

74 WwW

183.

85

I Re

186.207

76 Os

190.2

77 Ir

192.22

78 Pt

195.

08

79

Au

196.967

80

Hg

200.59

81 Tl204.383

$2 Pb

207.2

83 Bi

208.

908

84 Po

(209)

85 At

(210)

86 Rn

(222)

87

Fr (223)88 R

a 226.025] (260)103

104

Lr

Rf

(261

) 105

Db

(262

) 10

6

Sg

(263

) 10

7

Bh

(264)

108

Hs

(265)

109

Mt

(268)

110

Uun

(269)

111

Uuu

(272)

112

Uub

(269)

114

Uuq

116

Uuh

118

Uuo

Lanthanides:

Actinides:

57 La

138.

906

58 Ce

140.12

59 Pr

140.908

60

Nd

144.24

61 Pm

(145)

62 Sm

150.

36

63 Eu

151.

96

64

Gd

157.25

65 Tb

158.

925

66

162.50

67 Ho

161.

930

68

Er

167.26

69

Tm

166.

934

70 Yb

173.04 8

9

Ac

227.

028

90

Th

232.038 91 P

a231.036

92 U 238.029

93 Np

237.048

94

Pu

(244

) 95 Am

(243

) 9

6

Cm

(247)

97 Bk

(247

)

98 Cf (251)

99 Es

(252)

100

Fm

(257)

101

Md

(258

) 10

2

No

(259

)