HHmIBIH UNIVERSITY

OF SCIENCE nnD TECHNOLOGY

FACULTY OF HEALTH AND APPLIED SCIENCES

DEPARTMENT OF NATURAL AND APPLIED SCIENCES

QUALIFICATION: BACHELOR OF SCIENCE

QUALIFICATION CODE: O7BOSC LEVEL: 5

COURSE CODE: GNCSOZS COURSE NAME: GENERAL CHEMISTRY 13

SESSION: JANUARY 2018 PAPER: THEORY

DURATION: 3 HOURS MARKS: 100

SUPPLEMENTARY/SECOND 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 clearlyPWN'." 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

THIS QUESTION PAPER CONSISTS 0F 11 PAGES (Including this front page and attachments)

SECTION A

QUESTION 1: Multiple Choice Questions

[50]

[50]

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

2 marks.

0 Answer ALL questions by selecting the letter of the correct answer.

0 Choose the best possible answer for each question, even ifyou think there is

another possible answer that is not given.

1. 2N0 (g) + 2H2 (g) a N2 (g) + 2H20 (g)

Which of the following is true regarding the relative molar rates of disappearance

of the reactants and the appearance ofthe products?

I. N2 appears at the same rate that H2 disappears.

||. H20 appears at the same rate that NO disappears.

Ill. NO disappears at the same rate that H2 disappears.

A. Ionly.

B land ll only.

C land l|| only.

D. H and Illonly.

E l, II and III.

2. Forthe reaction 2A + B 9 C, experimental data was collected for three trials:

Experiment [A] (M) [B] (M) Initial Rate Appearance ofC (M sec‘l)

1 0.40 0.20 5.5 x 10'3

2 0.80 0.20 5.5 x 10'3

3 0.40 0.40 2.2 x 10'2

What is the rate law of the reaction?

Rate = k[A][B]

. Rate = k[A]°[B]2

. Rate = k[A]2[B]°

Rate = k[A][B]2

A.

B

c. Rate = k[A]2[B]2

D

E

Page 2 of 11

3. For a reaction A + B 9 C + D, the energy of activation and enthalpy change of reaction were

found to be 80 kJmoI'1 and + 20 kJmol'l, respectively. What is the value of the activation

energy for the reverse reaction?

A. + 60 kJmol‘1

B. + 100 kJmol’1

C. -80 kJmoI"1

D . +20 kJmol'1

E. lnsufficientinformation

4. Write the appropriate equilibrium constant expression Kc for the following reaction:

2C0(g) + 02(8) ‘—7 2C02(g)

A. Kc = k[COz][02]

B. Kc = [C02]/ [c0] [02]

c. I<c = [c0]2 [02] / [COzi

D. Kc = [c0212 / [CO] [02]

E. Kc = [C02]2 / [c0]2 [02]

5. Suppose we rewrote the balanced reaction in Question 4 above as:

COlg) + 1/: Ozlg) : coz(g)

What would be the equilibrium constant, K, forthis reaction be?

A. Same, Kc' = Kc

B. Kc' = (KC)V2C. Kc' = Kc/Z

D. c’ = K.2

E. Kc' = 1/ Kc

6. if Keq is small, it indicates that equilibrium occurs

At a low product concentration

At a high product concentration

After considerabletime.009"? With the help of a catalyst

E. With no forward reaction

Page 3 of 11

7. Arrhenius would definea base as Arrhenius would definea base as;

l. Something which yields hydroxide ions in solution

/I. A proton acceptor

lll. An electron pair donor

A. I, llandlll

B. landlll

C. II only

D. Ionly

E. landll

8. Calculate the concentration (mol/L) ofa solution of Ba(OH)2 that has pH of 12.7?

1 x 10'13

5 x 10'2

2 x 10'13

2.5 x 10'2

1.27 x 101P190530?9. 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 ofthis buffer solution, assuminga final volume of

500 mL and Kb: 1.8 x 10-5?

1.08

4.96

5.8

9.03

8F1909“?10. The oxidation number ofeach chromium atom in Cr2072‘ is

A. +5

+6

+7

+12

All of the aboveW90?”11. In which of the following unbalanced reactions does chromium undergo oxidation?

A. Cr3+—>Cr

B. Cr3+ —> Cr2+

c. Cr3+—>Cr2072'

D. Noneoftheabove

Page 4 of 11

12. In Copper Oxide (CuO) and Carbon Monoxide(CO) reaction, reducing agent is;

A. CuO

B. CO

C. Cu

D. C02

13. The ion PO43' has how man valence electrons?

A. 14

24

27

29

32.moosr14. What is the formal charge on sulphurin the Lewis structure below?

2..

IO:.. II ..

IO—S——01..

H..

102

A. -2

B. O

C. +2

D. +4

E. -4

15. How manydifferenttypes of resonance structures can be drawn forthe ion 5032' where all

atoms satisfythe octet rule?

1

511.0093? (11wa16. The electron-domain geometry of is tetrahedral.

A. CBr4

PH3

CCIzBrz

XeF4

All of the above except XeF4W909”Page 5 of 11

17. The bond angles marked a, b and c in the molecule beloware about,

and , respectively.

90°, 90°, 90°

120°, 120°, 90°

20°, 120°, 109.5°

109.5°, 120°, 109.5°

109.5°, 90°, 120°WPDPJ?18. What is the hybridization ofiodine in |F3 and IFS?

sp3, sp3d

sp3d,sp3d2

sp3d,sp3

sp3d2, sp3d111.0093?19. In comparingthe same two atoms bonded together, the the bond order, the

the bondlength,andthe the bond energy.

greater, shorter, greater

greater, greater, greater

greater, longer, greater

smaller, longer, smaller

smaller, greater, greater111.0093?20. How are the molecules in the following pair related?

l\lH :6Hand

H30 CH3 Hsc/glyH

They are constitutional isomers

They are stereoisomers

They are resonance structures

They are unrelated

The molecules are the sameW909”?21. Capsaicin is the spicy component of hot chilli peppers, and its structure is given below. What

is the correct molecularformula for this interesting molecule?

‘P/O

I\ NW|

HHO

/

capsaicin

(spicy component of hot peppers)

Page 6 of 11

C18H27N03

C18H25N03

C18H30N03

C17H25N03

C18H28N03.mPOFDP22. Which two particles have the same mass but opposite charge?

A. a beta particle and a positron

a neutron and a proton

a proton and an electron

an alpha particle and a proton

None of the aboveF190?”23. Complete the following nuclear equation:

0?$ '3205+ —|B

A. “3305

B. “£05

C. '33"

D. ‘3; Re

E. 1:? Os

24. Which molecules contain both covalent and ionic bonds?

CH30H N33C03 NH4CI NaCl

I II III IV

I and II

II and IV

I, II and IV.0057”? II and Ill

25. The half-life of 222Rn is 3.80 days. If a sample contains 36.0 g of 222Rn, how many years will

it take for the sampleto be reduced to 1.00 mg of 222Rn?

A. 19.7 g

B. 0.1597 g

c. 8.53 g

D. 0.0234 g

E. none of the above

Page 7 of 11

SECTION B:

QUESTION 1

i) Given the reaction below:

2503 (g) ‘—-, 2502 (g) + 02 (g) AH” = +197 kJ

Indicate ifthe number of moles of $03 will increase, decrease or remain the same in

the followingsituations:

(a) Oxygen gas is added.

(b) The pressure is increased by decreasingthe volume of the reaction container.

(c) The temperature is decreased.

(d) Gaseous sulphur dioxideis removed.

ii) Calculate the molar solubilityof Mg(OH)2 (KSp = 1.8 x 10'“) in:

(a) Pure water

(b) 0.0862 M MgClz(aq)

QUESTION 2

i) Find the oxidation number ofthe indicated atom in each of the following:

(a) Sin 5042‘

(b) N in N02-

(C) CI'II’I K2CI'207

ii) Balance the following halfreactions:

(a) CrO42' (aq) 9 Cr(OH)3(s) in basic medium

(b) HN02(aq) 9 NH);+ (aq) in acidic medium

QUESTION 3

Predict the electron domain and moleculargeometries ofthe following molecules or ions.

(a) Ang

(b) CH3+

(c) ClOg'

(d) Xer

(e) BrOZ-

Page 8 of 11

[50]

[14]

(2)

(2)

(2)

(3)

(3)

[12]

(2)

(2)

(2)

(3)

(3)

[5]

QUESTION 4 [6]

Radium-226 undergoes alpha decay and has a half—life of 1600 years.

(a) How manyalpha particles are emitted in 5.0 minutes bya 10.0 mg sample omea? (4)

(b) What is the activity of the sample in mCi? (2)

QUESTION 5 [4]

What orbital hybridization would be expected forthe central atom in each of the followingmolecule or ions?

(a) PCIG'

(b) PCl5

(c) Triiodideion

(d) Phosphoroustribromide

QUESTIONe [5]

Identifythe functional groups in the molecule below.

I

HOWl/HJLN/

O NH2

Aspartame

QUESTION 7 [4]

Redraw thefollowing reactions and add curved arrows to indicate theflow of electrons in each.

(a) 'O. 'O"/

'

\H+ H—Cl

——‘"

+ 01‘

(b)

THE END

GOODLUCK

Page 9 of 11

USEFUL CONSTANTS:

Gas constant, R = 8.3145 J 'mol'l' K‘1

= 0.083145 dm3-bar-mol'1- K'1

= 0.08206 L atm mol'l' K'1

1Pa'm3=1kPa.L =1N'm =1]

1 atm = 101 325 Pa = 760 mmHg = 760 torr

Avogadro’s Number, NA = 6.022 x 1023 mol‘1

Planck’s constant, h = 6.626 x 10'34 J5

Speed of light, c = 2.998 x 108 ms'1

Page 10 of 11

PERIODICTABLEOFTHEELEMENTS

1

18

1

2

H

He

1.00794

2

‘3

14

‘5

‘6

'7

4.00260

3

4

5

6

7

8

9

10

Li

Be

B

C

N

0

F

Ne

6.941

9.01218

10.81

12.011

14006715999418.998420.179

11

12

13

14

15

16

17

18

Na

Mg

A1

Si

P

S

Cl

Ar

22.989824.305

3

4

5

6

7

8

9

10

H

12

26.981528.085530.9738

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

50.941551.996

54.938055.84758.9332

58.69

63.546

6538

69.72

7259

74.9216

78.96

79.904

83.8

37

38

39

4O

41

42

43

44

45

46

47

48

49

50

51

52

53

54

Rb

Sr

Y

Zr

Nb

Mo

Tc

RuRthAg

Cd

In

Sn

Sb

Te

I

Xe

85.4678

87.62

88.9059

91.22

92.9064

95.94

(98)

10107102906106.42107.868112.41114.82

118.69

121.75

127.6

126.9

131.29

Page 11 of 11

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

08

Ir

Pt

Au

Hg

Tl

Pb

Bi

Po

At

Rn

132.905

137.33

174.967178.49180.948183.85

186207

190.2

19222

195.08

196.967200.59

204.383

2072

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

Ullh

U110

(223)

226.025

(260)

(261)

(262)

(263)

(264)

(265)

(268)

(269)

(272)

(269)

Lanthlnidw:

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

138.906l40.12140.908144.24(145)

15036

151.96

157.25158.925162.50161.930167.26166.934173.04

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

227.028232.038231.036238.029237.048

(244)

(243)

(2a

(247)

(251)

(252)

(257)

(258)

(259)