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APP601S - ANALYTICAL PRINCIPLES AND PRACTICE - 2ND OPP - JULY 2023 |
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nAm I BIA UnlVERSITY
OF SCIEnCE RnD TECHnOLOGY
FACULTYOF HEALTH,NATURAL RESOURCESAND APPLIEDSCIENCES
DEPARTMENT OF BIOLOGY, CHEMISTRY AND PHYSICS
QUALIFICATION: BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC
LEVEL: 6
COURSE CODE: APP601S
COURSE NAME: ANALYTICALPRINCIPLESAND
PRACTICE
SESSION: JULY 2023
DURATION: 3 HOURS
PAPER: THEORY
MARKS: 100
SUPPLEMENTARY/SECONDOPPORTUNITY EXAMINATION PAPER
EXAMINER(S) DR EUODIA HESS
MODERATOR: DR MARIUS MUTORWA
PERMISSIBLEMATERIALS
Non-programmable Calculators
ATTACHMENTS
List of useful tables, formulas and constants
THIS EXAMINATION PAPER CONSISTS OF 10 PAGES (Including this front page and
attachments)
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Question 1: Multiple Choice Questions
[30]
1.1 Which of the following glassware is not recommended for accurate measurements
of volumes?
(3)
(A) A graduated cylinder
(B) A volumetric flask
(C) A volumetric pipette
(D) A measuring pipette
1.2 NAM POL needs a more reliable method than the breathalyser test for detecting
the presence and the amount of alcohol in suspected drunk drivers. Solving this
problem requires
(3)
(A) Qualitative analysis
(B) Quantitative analysis
(C) Fundamental analysis
(D) All of the above
1.3 A guideline specifying how procedure must be followed is called
(3)
(A) An analytical approach
(B) A protocol
(C) A technique
(D) A method
1.4 The middle value of a series of data ordered from the smallest to the largest value
is called
(3)
(A) Average
(B) Median
(C) Arithmetic mean
(D) Geometric mean
1.5 Which substance, when added to water, will not change the pH?
(3)
(A) NaHC03
(B) NH4CI
(C) KCN
(D) KCI
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1.6 What is the pH of a saturated solution of milk of magnesia, Mg(OH)z, if the Ksp of
this compound is 1.2 x 10- 11?
(3)
(A) 3.5
(B) 9.2
(C) 10.5
(D) 10.9
1.7 Bleaching powder reacts with iodide ion according to the following unbalanced
equation: oc1-+ r + W 12+ c1-+ H2O
A 0.6000 g sample of bleaching powder requires 35.24 ml of 0.1084 M Na2S2O3to
titrate the liberated iodine. The percentage of Cl in the sample is
(3)
(A) 22.58% Cl
(B) 5.15% Cl
(C) 11.29% Cl
(D) 45.16% Cl
1.8 Given the following half-reactions:
A2+ + e- - N
E0 = +1.70 V
B4+ + 2e- - B2+ E0 = +0.60 V
c c 3+ + e- - 2+
E0 = +0.90 V
The only reaction that could be used in a titration would be
(3)
(A) N with B4+
(B) N with C3+
c (C)A2+ with 2+
c (D) 2+ with B4+
1.9 During a potentiometric oxidation-reduction titration, the only place at which the
Ecellequals the E0 of the substance being titrated is
(3)
(A) when the two half reactions are in equilibrium
(B) when twice the stoichiometric amount of titrant has been added
(C) at the equivalence point
(D) half way to the equivalence point
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1.10 A standard solution of 0.154 M HCI is used to determine the concentration of a
NaOH solution whose concentration is unknown. If 33.5 ml of the acid solution
are required to neutralize 25.0 ml of the base solution, the concentration of the
NaOH in moles/liter is
(3)
(A) 25.0 / (0.154)(33.5)
(B) (0.154)(25.0) / 33.5
(C) (33.5 + 25.0) / 0.514
(D) (0.514)(33.5) / 25.0
Question 2
[15]
2.1 To test a spectrophotometer's accuracy a solution of 60.06 ppm K2Cr2Oi1n 5.0 mM
H2SO4is prepared and analysed. This solution has an expected absorbance of 0.640
at 350.0 nm in a 1.0-cm cell when using 5.0 mM H2SO4as a reagent blank. Several
aliquots of the solution produce the following absorbance values.
0.639
0.638 0.640 0.639 0.640 0.639
0.638
(a) Calculate the mean and standard deviation of the measured absorbance values. (2)
(b) Determine whether there is a significant difference between the experimental
mean and the expected value at a= 0.01 (i.e. P= 99%).
(6)
2.2 One way to check the accuracy of a spectrophotometer is to measure absorbencies
for a series of standard dichromate solutions obtained from the National Institute
of Standards and Technology. Absorbencies (A) are measured at 257 nm and
compared to the accepted values. The results obtained when testing a newly
purchased spectrophotometer are shown below.
Standard
1
2
3
4
5
Measured A
0.2872
0.5773
0.8674
1.1623
1.4559
Expected A
0.2871
0.5760
0.8677
1.1608
1.4565
Determine if the tested spectrophotometer is accurate at a= 0.05.
(7)
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Question 3
[15]
3.1 A solution containing 3.47 mM of analyte and 1.72 mM of standard gave peak areas
of 3,473 and 10,222, respectively, in a chromatographic analysis. Then 1.00 ml of
8.47 mM standard was added to 5.00 ml of unknown solution, and the mixture was
diluted to 10.0 ml. This solution gave peak areas of 5 428 and 4 431 for the analyte
and standard, respectively.
(a) Calculate the response factor for the analyte.
(2)
(b) Find the concentration of the standard in the 10.0 ml of mixed solution.
(2)
(c) Find the analyte concentration in the 10.0 ml of mixed solution.
(2)
(d) Find the analyte concentration in the original unknown.
(2)
3.2 The concentration of phenol in a water sample is determined by separating the
phenol from non-volatile impurities by steam distillation, followed by reacting with
4-aminoantipyrine and K3Fe(CN)5at pH 7.9 to form a colored antipyrine dye.
A phenol standard with a concentration of 4.00 ppm has an absorbance of 0.424.
A water sample is steam distilled and a 50.00-ml aliquot of the distillate is placed in
a 100-ml volumetric flask and diluted to volume with distilled water. The absorbance
of this solution is found to be 0.394.
(a) What is the concentration of phenol (in parts per million) in the water sample? (4)
(b) What calibration method has been used here?
(1)
(c) Briefly explain your choice of the calibration method.
(2)
Question 4
[15]
4.1 For the following unbalanced reaction at 25°C
Fe2+ +Mno4- D Fe3+ + Mn 2+ (acidic medium)
(E°Fe3+/Fe2+ = 0.771 V; E0MnO4-/Mn2+ = 1.51 V)
(a) Write the balanced oxidation and reduction half reactions as well as the overall
reaction.
(3)
(b) Calculate the standard potential of the reaction.
(1)
(c) Calculate the equilibrium constant of the reaction.
(2)
(d) Calculate the potential under the following conditions: [Fe2+] = 0.50 M,
[Fe3+] = 0.10 M, [Mno4-J = 0.025 M, [Mn 2+] = 0.015 M, and a pH of 7.00.
(2)
4.2 Calculate the pH of the solution that results from the addition of 0.040 moles of
HNO3to a buffer made by combining 0.500 l of 0.380 M HC3HsO2(Ka=1.30 x 10- 5)
and 0.500 l of 0.380 M NaC3HsO2A. ssume addition of the nitric acid has no effect
on volume.
(5)
4.3 Calculate the ionic strength of a 0.025 M solution of CuCli
(2)
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Question 5
[35]
5.1 50.0 ml of 0.0400 M formic acid (HCOOH,Ka= 1.80 x 10-4) was titrated with
0.120 M NaOH.
(a) Write the balanced reaction of the titration.
(2)
(b) calculate the volume of added titrant at the equivalence point.
(1)
(c) Calculate the pH after addition of the following volumes of the titrant
(i) 0.0 ml
(4)
(ii) 10.0 ml
(4)
(iii) 20.0 ml
(4)
5.2 25.0 ml of 0.01 M v2+ is titrated using 0.01 M Ce4+
(E0v3+/V2+ = - 0.255 V; E0ce4+/Ce3+ = + 1.72 V).
(a) Write the two redox half-reactions, the overall reaction and the potential (E)
expressions for both redox half-reactions.
(5)
(b) Calculate the potential of the titration after addition of
(i) 15.0 ml Ce4+
(5)
(ii) 25.0 ml Ce4+
(5)
5.3 (a) Define gravimetry.
(1)
(b) List the different types of gravimetric methods.
(4)
END
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Data Sheet
l calculated
-Jn !!_ fcalculated =
Sd
Spooled=
s;(Na -l)+s~(Nb-1)+ ....... .
Na +Nb + ...... -Nsetsofdata
Confidence
degrees
Freedom
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
50%
1.000
0.816
0.765
0.741
0.727
0.718
0.711
0.706
0.703
0.700
0.697
0.695
0.694
0.692
0.691
0.690
0.689
0.688
0.688
0.687
0.686
0.686
0.685
0.685
0.684
0.684
0.684
0.683
0.683
0.683
0.682
0.682
0.682
0.682
0.682
90%
6.314
2.920
2.353
2.132
2.015
1.943
1.895
1.860
1.833
1.812
1.796
1.782
1.771
1.761
1.753
1.746
1.740
1.734
1.729
1.725
1.721
1.717
1.714
1.711
1.708
1.706
1.703
1.701
1.699
1.697
1.696
1.694
1.692
1.691
1.690
95%
12.706
4.303
3.182
2.776
2.571
2.447
2.365
2.306
2.262
2.228
2.201
2.179
2.160
2.145
2.131
2.120
2.110
2.101
2.093
2.086
2.080
2.074
2.069
2.064
2.060
2.056
2.052
2.048
2.045
2.042
2.040
2.037
2.035
2.032
2.030
99%
63.656
9.925
5.841
4.604
4.032
3.707
3.499
3.355
3.250
3.169
3.106
3.055
3.012
2.977
2.947
2.921
2.898
2.878
2.861
2.845
2.831
2.819
2.807
2.797
2.787
2.779
2.771
2.763
2.756
2.750
2.744
2.738
2.733
2.728
2.724
Critical Values for the Rejection Quotient
Qc,;t(Reject if Q,,xp> Qc,;t)
N
90%
95%
99%
Confidence Confidence Confidence
3
0.941
0.970
0.994
4
0.765
0.829
0.926
5
0.642
0.710
0.821
6
0.560
0.625
0.740
7
0.507
0.568
0.680
8
0.468
0.526
0.634
9
0.437
0.493
0.598
10
0.412
0.466
0.568
N = number of observations
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F(0.05, onum, odenom) for a Two-Tailed F-Test
1
2
3
4
5
odenU
1
647.8 799.5 864.2 899.6 921.8
2
38.51 39.00 39.17 39.25 39.30
3
17.44 16.04 15.44 15.10 14.88
4
12.22 10.65 9.979 9.605 9.364
5
10.01 8.434 7.764 7.388 7.146
6
8.813 7.260 6.599 6.227 5.988
7
8.073 6.542 5.890 5.523 5.285
8
7.571 6.059 5.416 5.053 4.817
9
7.209 5.715 5.078 4.718 4.484
10
6.937 5.456 4.826 4.468 4.236
11
6.724 5.256 4.630 4.275 4.044
12
6.544 5.096 4.474 4.121 3.891
13
6.414 4.965 4.347 3.996 3.767
14
6.298 4.857 4.242 3.892 3.663
15
6.200 4.765 4.153 3.804 3.576
16
6.115 4.687 4.077 3.729 3.502
17
6.042 4.619 4.011 3.665 3.438
18
5.978 4.560 3.954 3.608 3.382
19
5.922 4.508 3.903 3.559 3.333
20
5.871 4.461 3.859 3.515 3.289
00
5.024 3.689 3.116 2.786 2.567
6
937.1
39.33
14.73
9.197
6.978
5.820
5.119
4.652
4.320
4.072
3.881
3.728
3.604
3.501
3.415
3.341
3.277
3.221
3.172
3.128
2.408
7
948.2
39.36
14.62
9.074
6.853
5.695
4.995
4.529
4.197
3.950
3.759
3.607
3.483
3.380
3.293
3.219
3.156
3.100
3.051
3.007
2.288
8
956.7
39.37
14.54
8.980
6.757
5.600
4.899
4.433
4.102
3.855
3.644
3.512
3.388
3.285
3.199
3.125
3.061
3.005
2.956
2.913
2.192
9
963.3
39.39
14.47
8.905
6.681
5.523
4.823
4.357
4.026
3.779
3.588
3.436
3.312
3.209
3.123
3.049
2.985
2.929
2.880
2.837
2.114
10
968.6
39.40
14.42
8.444
6.619
5.461
4.761
4.259
3.964
3.717
3.526
3.374
3.250
3.147
3.060
2.986
2.922
2.866
2.817
2.774
2.048
15
984.9
39.43
14.25
8.657
6.428
5.269
4.568
4.101
3.769
3.522
3.330
3.177
3.053
2.949
2.862
2.788
2.723
2.667
2.617
2.573
1.833
20
993.1
39.45
14.17
8.560
6.329
5.168
4.467
3.999
3.667
3.419
3.226
3.073
2.948
2.844
2.756
2.681
2.616
2.559
2.509
2.464
1.708
00
1018
39.50
13.90
8.257
6.015
4.894
4.142
3.670
3.333
3.080
2.883
2.725
2.596
2.487
2.395
2.316
2.247
2.187
2.133
2.085
1.000
Physical Constants
Gas constant
R
Boltzmann constant
k
Planck constant
h
Faraday constant
F
Avogadro constant
Speed of light in vacuum
C
Mole volume of an ideal gas
Vm
= 22.71 L moI- 1 (at 1 bar and 273.15 K)
Elementary charge
e
Rest mass of electron
me
Rest mass of proton
mp
Rest mass of neutron
mn
Permitivity of vacuum
co
Gravitational acceleration
g
= 8.315 J K-1 moI- 1
= 8.315 kPa dm 3 K-1 moI- 1
= 8.315 Pa m 3 K-1 moI- 1
= 8.206 x 10-2 L atm K-1 moI- 1
= 1.381 x 10-23 J K-1
= 6.626 x 10-34 J K-1
= 9.649 x 104 C moI- 1
= 6.022 x 1023 moI- 1
= 2.998 x 108 m s-1
= 22.41 L moI- 1 (at 1 atm and 273.15 K)
=1.602 X 10-19 C
=9.109 x 10-31 kg
=1.673 X 10-27 kg
=1.675 X 10-27 kg
=8.854 x 10-12 C2 J-1 m-1 (or F m-1)
=9.807 m s-2
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Conversion Factors
lW
1J
1 cal
1 eV
1 L atm
1 atm
1 bar
1L
1 Angstrom
1 micron(µ}
1 Poise
1 ppm
ssamp
CA_VVo
f
+ V
C __£_
V A
V
C
51:d
V
f
f
= 1 J s-1
= 0.2390 cal = 1 N m = 1 V C
= 1 Pa m3 =1 kg m2 s-2
= 4.184 J
= 1.602 X 10-19 J
= 101.3 J
= 1.013 x 105 N m-2 = 1.013 x 105 Pa =
760 mmHg
= 1 x 105 Pa
= 10-3 m3 = 1 dm 3
= 1 x 10-10 m = 0.1 nm = 100 pm
=10-6 m =1 µm
= 0.1 Pas= 0.1 N sm-2
= 1 ~Lgg-1 = 1 mg kg-1
= 1 mg L·1 (dilute aqueous solutions only}
s,runp -
c
V
O
"V+V
o
S'Pike
+c
V
"d
,,dV+V
,id
o
,id
llG 0 = -RT lnK
E 0 = 0.05916 logK
n
Eo=Eo -Eo
ml
ca:
E = Eo _
0.05916 logQ
n
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PERIODIC TABLE OF THE ELEMENTS
18
l
2
H
1.00794 2
13
14
15
He
16
17 4.00260
34
5 6 7 8 9 10
Li Be
B C N 0 F Ne
6.941 9.01218
10.81 12.011 14.0067 15.9994 18.9984 20.179
11 12
Na Mg
22.9898 24.305 3
4
5
6
13 14 15 16 17 18
Al Si p s Cl Ar
7
8
9
10
11
12 26.9815 28.0855 30.9738 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 50.9415 51.996 54.9380 55.847 58.9332 58.69 63.546 6538 69.72 72.59 74.9216 78.96 79.904 83.8
'.-,c.l ,
(IQ
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
C.i)...
Rb Sr y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Q
0........,
85.4678 87.62 88.9059 91.22 92.9064 95.94 (98) 101.07 102.906 106.42 107.868 112.41 114.82 118.69 121.75 127.6 126.9 13129
55 56 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
Q
Cs Ba Lu Hf Ta w Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
132.905 137.33 174.967 178.49 180.948 183.85 186207 190.2 192.22 195.08 196.967 200.59 204383 207.2 208.908 (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
(223) 226.025 (260) (261) (262) (263) (264) 265) '268) (269) (272) (269)
Uuh
Uuo
Lanthanides: 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
138.906 140.12 140.908 14424 (145) 15036 151.96 157.25 158.925 162.50 161.930 167.26 166.934 173.04
Actinides:
89 90 91 92 93 94 95 96 97 98 99 100 IOI 102
Ac Th Pa V Np Pu Am Cm Bk Cf Es Fm Md No
227.028 232.038 231.036 238.029 237.048 (244) (243) (247) (247) (251) (252) (257) (258) (259)