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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)
Page12
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