I e

I'IRITIIBIFI UNIVERSITY

OF SCIEI'ICE FII'ID TECHNOLOGY

FACULTY OF HEALTH AND APPLIED SCIENCES

DEPARTMENT OF NATURAL AND APPLIED SCIENCES

QUALIFICATION: BACHELOR OF SCIENCE

QUALIFICATION CODE: O7BOSC LEVEL: 6

COURSE CODE: APP601$COURSE NAME: ANALYTICAL PRINCIPLES AND

PRACTICE

SESSION: JULY 2017 PAPER: THEORY

DURATION: 3 HOURS MARKS: 100

SUPPLEMENTARY/SECOND OPPORTUNITY EXAMINATION QUESTION PAPER

EXAMINER(S) DrJULIEN LUSILAO

MODERATOR:Prof OMOTAYO AWOFOLU

INSTRUCTIONS

1. Answer ALL the questions in the answer book provided.

2. Write and number your answers clearly.

3. All written work MUST be done in blue or black ink.

PERMISSIBLE MATERIALS

Non-programmable Calculators

ATTACHMENT

List of Useful Tables, formulas and Constants

THIS QUESTION PAPER CONSISTS OF 12 PAGES (Including this front page and List of Useful

Tables, formulas and Constants)

Question 1: Multiple Choice Questions [45]

0 Choose the best possible answer for each question.

1.1 A mass of 5.4 grams of aluminum (Al) reacts with an excess of copper (ll) chloride

(CuClz) in solution, as shown below.

3CuCl2 + 2Al 9 2AlCl3 + 3Cu

What mass of solid copper (Cu) is produced? (3)

(A) 0.65 g

(B) 8.5 g

(C) 13 g

(D) 19 g

1.2 A human patient suffering from a duodenal ulcer may show a hydrochloric acid

concentration of 0.080 mol/liter in his gastricjuice. it is possible to neutralize this

acid with aluminum hydroxide, A|(OH)3, which reacts with HCl according to the

balanced chemical equation

Al(OH)3 + 3HC| 9 AlCl3 + 3H20

If the patient's stomach receives 3.0 liters of gastric juice per day, how much

aluminum hydroxide must he consume per day to counteract the acid? (3)

(A) 6.2 g

(B) 19 g

(C) 26 g

(D) 78 g

1.3 What is the molarity ofthe sulfate ion in a solution prepared by dissolving 17.1 g of

aluminum sulfate, A|2(SO4)3, in enough water to prepare 1.00 L of solution. Neglect

any hydrolysis. (3)

(A) 1.67 x 10'2 M

(B) 5.00 x 10‘2 M

(C) 1.50 x 10'1 M

(0) 2.50 x 10'1 M

1.4 The net ionic equation for the precipitation reaction that occurs when aqueous

solutions of AgNO; and K2CrO4 are mixed is (3)

(A) K+ + N03’ ---> KN03(s)

(B) Ag+ + CrO4' ---> AgCrO4(s)

(C) K2++ N03" ---> K2N03(s)

(D) 2Ag+ + 00.3" ---> AgZCrO4(s)

1.5 A reaction for which AH < 0 and AS < 0 is most likely to have which of these

thermodynamic properties? (3)

(A) The reaction cannot be spontaneous at any temperature.

(B) The reaction will tend to be spontaneous at low temperatures.

(C) The reaction will tend to be spontaneous at high temperatures.

(D) The spontaneity of the reaction will be independent of temperature.

1.6 Consider the equilibrium reaction

4NH3(g) + 302(g) e 2N2(g) + 6H20(g) AH = -1268 kJ

Which change will cause the reaction to shift to the right? (3)

(A) Increase the temperature

(B) Decrease the volume of the container.

(C) Add a catalyst to speed up the reaction.

(D) Remove the gaseous water by allowing it to react and be absorbed by KOH.

1.7 2.00 moles of NO and an undetermined amount of 02 are placed in a 1L container

at 460°C. When the reaction

2NO(g) + 02(g) H 2N02(g)

reaches equilibrium, we find 0.00156 mol of Oz and 0.500 mol of N02. The value of

the equilibrium constant for this system is (3)

(A) 4.42

(B) 40.1

(C) 71.2

(D) 214

1.8 Consider the following reaction at equilibrium in a container of constant volume:

2502(g) + 02(g) H 2503(g) AH = -7.8 kcal

Which of the following would result in a greater concentration of 502? (3)

(A) addition of 02

(B) addition of 303

(C) removal of 503

(D) a decrease in temperature

1.9 In the reaction

6K! + 2KMnO4 + 4H20 9 Biz + 2Mn02 + 8KOH

which atom undergoes oxidation? (3)

(A) K

(B) Mn

(C) 0

(D) |

1.10 Given the standard reduction potentials

Cu2++ 2e” 9 Cu(s) E“ = +0.34 v

AI3+ + 3e" e—> AI(s) E° = —1.66 v

Calculate the standard voltage for the reaction

2Al(s) + 3Cu2+9 2Al3+ + 3Cu(s) (3)

(A) -1.22 V

(B) +2.00 V

(C) +4.34 v

(D) +5.86 v

1.11 Given the standard electrode (reduction) potentials:

Cd2*(aq) + 2e' 9 Cd(s) E" = -0.40 v

Ag+(aq) + e'-> Ag(s) E° = +0.80 V

What would be the E° for a cadmium—silver cell?

(A) 0.4 v

(B) 0.5 v

(C) 1.2 v

(D) 2.0 v

1.12 A reaction has positive values of both AS“ and AH°. From this you can deduce that

the reaction

(A) must be spontaneous at any temperature.

(B) cannot be spontaneous at any temperature.

(C) will be spontaneous only at low temperatures.

(D) will be spontaneous only at high temperatures.

1.13 The equilibrium constant for the below reaction is

Ag+(aq) + l'(aq) <9 Ag|(s) AGO = -91.9 kJ mol'1

(A) 7.78 x 10'17

(B) 1.29 x 1016

(C) 1.24 x 1037

(D) 37.1

1.14 The pH of a solution of vinegar is 3.00. The concentration of OH" ion in this

solution is

(A) 3.00 M

(B) 1 x 10'3 M

(C) 1 x 10'11 M

(D) 17 M

(3)

(3)

1.15 When conducting analyses of substances that are weak acids by titrating

solutions with a standardized strong base, the end-point indicator is chosen so

that (3)

(A) its color change occurs around the neutralization pH of 7.00.

(B) its color change occurs when the pH is about the same as the pKa of the weak acid.

(C) its color change occurs at a pH that is more basic than pH = 7.00.

(D) its color change occurs at a pH that is the same as that of the standardized base

solution.

Question 2 [8]

The Figure below shows a standard additions calibration curve for the quantitative

analysis of Mn2+. Each solution contains 25.00 mL (i.e.Vo) of the original sample and

either of 0; 2.0; 4.0; 6.0; 8.0; or 10.0 mg/L of external standard (Cstd) of an+_

All standard addition samples were diluted to 50.00 mL (Vf) before reading the

absorbance.

0.60,

0.50 :- y—intercept = flC—Avi: Vf

0.40:-

Sspike 0.305-

0202-

0.10}/0:...1...J..|..I...1.,.l...l-4.00

\-2.000 2.00 4,00 6.00 8.00 10.00 12.00

'

AC Vo Cstd x V‘sl—td (mg/L)Vf

fx-intercept =

The equation for the calibration curve in the Figure is

5..., = 0.0425 x cstdwstd/vf) + 0.1478

2.1 What is the concentration of Mn“ (CA in mg/L) in this sample? (5)

2.2 Express the obtained concentration in ppb and in molarity (M) (3)

Question 3 [10]

A researcher at NUST investigated the quantitative determination of Cr in high—alloy

steels using a potentiometric titration of Cr(Vl). A reference steel was analysed to

6

validate the used analytical method and the following results (as %w/w Cr) were

obtained:

16.968; 16.922; 16.840; 16.883; 16.887; 16.977; 16.857; 16.728

When analysing the obtained data, the researcher had some concerns about the last

measurement that showed 16.728% Cr.

3.1 Use the QTest to confirm the reliability ofthat measurement at 95%

confidence level. (5)

3.2 Would you come up with a similar conclusion as in 3.1 if a Grubb’s (G) Test

was used instead for the same confidence level? The following table is

provided for the Grubb’s Test.

G (95%)

1.115

1.481

1.715

1.887

2.020

2.126

2.215

2.290

k000\lCDU'l-PUJ:5H O

Question 4 [14]

For the following reaction at 25°C

5Fe2*(aq, + Mn04'(aq) + 8H+(aq) <—> 5Fe3*(aq, + Mn2*(aq,+ 4H20

The below conditions are provided:

[Fe2+] = 0.50 M, [Fe3+] = 0.10 M (WW/Fez. = 0.771 V)

[Mno4'] = 0.025 M, [Mn2*] = 0.015 M (E°Mno4./Mn2. = 1.51 V)

And a pH = 7.00

4.1 Write the two BALANCED half reactions and indicate the oxidation and

reduction. (4)

4.2 How many electrons are involved (exchanged) in the overall reaction? (1)

4.3 Calculate the standard potential (E0) of the reaction (2)

4.4 Calculate the reaction equilibrium constant (K) (2)

4.5 Give the expression of K based on the overall redox reaction (2)

4.6 Calculate the potential (E) under the above provided conditions (3)

Question 5 [19]

A solution containing 50.00 mL of 0.1800 M NH; (Kb = 1.77 x 10-5) is being titrated with

0.3600 M HCI. Calculate the pH:

5.1lnitially(i.e. before titration (3)

5.2 After the addition of 5.00 mL of HCI (5)

5.3 After the addition of a total volume of 12.50 mL HCI (3)

5.4 After the addition of a total volume of 25.00 mL of HCI (5)

5.5 After the addition of 26.00 mL of HCI (3)

Question 6 [4]

A rock sample is to be assayed for its tin content by an oxidation-reduction titration with

l3‘(aq). A 10.00 g sample of the rock is crushed, dissolved in sulfuric acid, and passed over

a reducing agent so that all the tin is in the form Snz”. The Sn2+(aq) is completely oxidized

by 34.60 mL of a 0.5560 M solution of Nalg. The balanced equation for the reaction is

l3'(aq) + Sn2+(aq) ---> Sn4+(aq) + 3|'(aq)

6.1 Determine the amount of triiodide used. (1)

6.2 Determine the Sn(ll) that reacted. (1)

6.3 Calculate grams of Sn(|l) ion (to four sig figs). (1)

6.4 Calculate mass percentage of Sn(ll) in the sample. (1)

END

DataSheet

Ix — IUI J— t = 1J3 toa/culaled =

X3 Xbl><

na X nb

toalculalud = N calculated

d Spoo/ed 1’ na + nb

SWIM:s§(Na—1)+s§(Nb—1)+ ........ _IX...-X Q

gap

Na + Nb + ......

— Nsetsof data up”1°

range

p=iili11

Confidence

degrees50% 90% 95% 99%

Critical Values for the Rejection Quotient

Freedom

1 1.000 6.314 12.706 63.656 th (Reject if Q.xp > Q...)2 0.816 2.920 4.303 9.925 N 90% 95% 99%

3 0-765 2-353 3-182 5-841 Confidence Confidence Confidence

4 0.741 2.132 2.776 4.6043 (1941 0970 0.994

5 0.727 2.015 2.571 4.032

6 0.718 1.943 2.447 3.7074 0765 0829 0'926

7 0.711 1.895 2.365 3.499 5 0-642 0-710 0-821

8 0.706 1.860 2.306 3.355 6 0.560 0.625 0.740

9 0.703 1.833 2.262 3.2507 0.507 0.568 0.680

10 0.700 1.812 2.228 3.169

11 0.697 1.796 2.201 3.1068 0.468 0526 0634

12 0.695 1.782 2.179 3.0559 0-437 0-493 0-598

13 0.694 1.771 2.160 3.012 10 0.412 0.466 0.568

14 0.692 1.761 2.145 2.977N = number of observations

15 0.691 1.753 2.131 2.947

16 0.690 1.746 2.120 2.921

17 0.689 1.740 2.110 2.898

18 0.688 1.734 2.101 2.878

19 0.688 1.729 2.093 2.861

20 0.687 1.725 2.086 2.845

21 0.686 1.721 2.080 2.831

22 0.686 1.717 2.074 2.819

23 0.685 1.714 2.069 2.807

24 0.685 1.711 2.064 2.797

25 0.684 1.708 2.060 2.787

26 0.684 1.706 2.056 2.779

27 0.684 1.703 2.052 2.771

28 0.683 1.701 2.048 2.763

29 0.683 1.699 2.045 2.756

30 0.683 1.697 2.042 2.750

31 0.682 1.696 2.040 2.744

32 0.682 1.694 2.037 2.738

33 0.682 1.692 2.035 2.733

34 0.682 1.691 2.032 2.728

35 0.682 1.690 2.030 2.724

F(0.05, onum, odenom) for a Two-Tailed F-Test

onum=> 1 2 3 4 5 6 7 8 9 10 15 20 co

odenU

1 647.8 799.5 864.2 899.6 921.8 937.1 948.2 956.7 963.3 968.6 984.9 993.1 1018

2 38.51 39.00 39.17 39.25 39.30 39.33 39.36 39.37 39.39 39.40 39.43 39.45 39.50

3 17.44 16.04 15.44 15.10 14.88 14.73 14.62 14.54 14.47 14.42 14.25 14.17 13.90

4 12.22 10.65 9.979 9.605 9.364 9.197 9.074 8.980 8.905 8.444 8.657 8.560 8.257

5 10.01 8.434 7.764 7.388 7.146 6.978 6.853 6.757 6.681 6.619 6.428 6.329 6.015

6 8.813 7.260 6.599 6.227 5.988 5.820 5.695 5.600 5.523 5.461 5.269 5.168 4.894

7 8.073 6.542 5.890 5.523 5.285 5.119 4.995 4.899 4.823 4.761 4.568 4.467 4.142

8 7.571 6.059 5.416 5.053 4.817 4.652 4.529 4.433 4.357 4.259 4.101 3.999 3.670

9 7.209 5.715 5.078 4.718 4.484 4.320 4.197 4.102 4.026 3.964 3.769 3.667 3.333

10 6.937 5.456 4.826 4.468 4.236 4.072 3.950 3.855 3.779 3.717 3.522 3.419 3.080

11 6.724 5.256 4.630 4.275 4.044 3.881 3.759 3.644 3.588 3.526 3.330 3.226 2.883

12 6.544 5.096 4.474 4.121 3.891 3.728 3.607 3.512 3.436 3.374 3.177 3.073 2.725

13 6.414 4.965 4.347 3.996 3.767 3.604 3.483 3.388 3.312 3.250 3.053 2.948 2.596

14 6.298 4.857 4.242 3.892 3.663 3.501 3.380 3.285 3.209 3.147 2.949 2.844 2.487

15 6.200 4.765 4.153 3.804 3.576 3.415 3.293 3.199 3.123 3.060 2.862 2.756 2.395

16 6.115 4.687 4.077 3.729 3.502 3.341 3.219 3.125 3.049 2.986 2.788 2.681 2.316

17 6.042 4.619 4.011 3.665 3.438 3.277 3.156 3.061 2.985 2.922 2.723 2.616 2.247

18 5.978 4.560 3.954 3.608 3.382 3.221 3.100 3.005 2.929 2.866 2.667 2.559 2.187

19 5.922 4.508 3.903 3.559 3.333 3.172 3.051 2.956 2.880 2.817 2.617 2.509 2.133

20 5.871 4.461 3.859 3.515 3.289 3.128 3.007 2.913 2.837 2.774 2.573 2.464 2.085

00 5.024 3.689 3.116‘

2.786 2.567 2.408 2.288 2.192 2.114 2.048 1.833 1.708 1.000

Physical Constants

Gas constant R = 8.315 J K‘1 mol'1

= 8.315 kPa dm3 K'1 mol'1

= 8.315 Pa m3 K'1 mol'1

= 8.206 x 10'2 L atm K'1 mol'1

Boltzmann constant k = 1.381 x 1023] K'1

Planck constant h = 6.626 x 10341 K“1

Faraday constant F = 9.649 x 104 C mol'1

Avogadro constant L or NA = 6.022 x 1023 mol'1

Speed of light in vacuum c = 2.998 x 108 m s'1

Mole volume of an ideal gas V,,1 = 22.41 L mol‘1 (at 1 atm and 273.15 K)

= 22.71 L mol'1 (at 1 bar and 273.15 K)

Elementary charge e = 1.602 x 10‘19 C

Rest mass of electron me= 9.109 x 10'31 kg

Rest mass of proton m,= 1.673 x 10'27 kg

Rest mass of neutron mn = 1.675 x 10'27 kg

Permitivity of vacuum 80 = 8.854 x 10‘12 c2 1'1 m'1 (or F m'1)

Gravitational acceleration g= 9.807 m s'2

10

Conversion Factors

1 w = 11 s'1

11 =0.2390ca|=1Nm=1VC

= 1Pam3=1kgmzs'2

1 cal = 4.184J

1 eV = 1.602 x 10191

1 L atm = 101.31

1 atm = 1.013 x 105 N m’2 = 1.013 x 105 Pa =

760 mmHg

1 bar = 1 x 105 Pa

1L =1O'3m3=1dm3

1 Angstrom = 1 x 101° m = 0.1 nm = 100 pm

1 micron (u) = 10'6m = 1 um

1 Poise = 0.1 Pa 5 = 0.1 N sm'2

1 ppm = 1 Mg g'1= 1 mg kg’1= 1 mg L'1 (dilute aqueous solutions only)

1]

H

AtomicNumber

[.0079 Li

Be

6941

9.0122

11

12

Na

Mg

22990

24305

N

He 4.0026

AtomicWeight

He 4.0026

B

C

N

O

F

Ne

10.811

12.011

14.007

15.999

18.998

20.179

13

14

15

16

17

18

Al

Si

P

S

Cl

Ar

26.982

28.086

30.974

32.064

35.453

39.948

I9

20

21

22

23

24

25

26

K

Ca

Sc

Ti

V

Cr

Mn

39.098

40.078

44.956

47.88

50.942

51.996

54.938

27

28

29

30

Fe

Co

Ni

Cu

55.847

58933

5869

63.546

Zn65.39

3|

32

33

34

35

36

GaGeAsSeBrKr 69.723

72.61

74.922

78.96

79.904

83.80

37

38

39

40

41

42

43

44

Rb

Sr

Y

Zr

Nb

M0

Tc

85.47

87.62

88.906

91.224

92.906

95.94

(98)

45

46

47

4

8

Ru

Rh

Pd

Ag

101.07

102.91

10642

107.87

Cd 112.41

49

50

51

52

53

54

In

Sn

Sb

Te

I

Xe

114.82

118.71

121.75

127.60

12690

131.29

55

56

S7

72

73

74

75

76

Cs

Ba

La

Hf

Ta

W

Re

132.91

13733

13891

178.49

180.95

183.85

186.2

77

78

79

80

Os

Ir

Pt

Au

190.2

192.22

19508

196.97

200.59

81

82

83

84

85

86

T1

Pb

Bi

P0

At

Rn

204.38

207.2

208.98

(209)

(210)

(222)

87

88

89

Fr

Ra

Ac

(223)

22603

2270358

59

60

61

62

Ce

Pr

Nd

Pm

140.12

140.91

144.24

146.92

63

64

65

66

Sm

Eu

Gd

Tb

150.3

151.97

157.25

158.93

Dy 162.50

68

69

70

71

Ho

Er

Tm

Yb

Lu

164.93

167.26

168.93

173.04

174.97

90

91

92

93

94

Th

Pa

U

Np

232.04

231.04

23803

237.05

95

96

97

98

Pu

Am

Cm

Bk

(241)

(234)

(247)

247

Cf(251)

100

101

102

103

Es

Fm

Md

N0

Lr

(252)

(357)

(258)

(259)

(360)

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