I

HHITIIBIH UNIVERSITY

OF SCIENCE nno 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: JUNE 2017 PAPER: THEORY

DURATION: 3 HOURS MARKS: 100

FIRST 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 11 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 An analytical balance is capable of measuring mass to the nearest 0.1 mg.

Which measurement correctly reflects the precision which can be obtained

when using this balance? (3)

(A) 2.06 g

(B) 2.060 g

(C) 2.0600 g

(0) 2.06000 g

1.2 Mg3N2(s) + 6H20(|) 9 2NH3(aq) + 3Mg(OH)2(s)

If 54.0 grams of water are mixed with excess magnesium nitride, then how

many grams of ammonia are produced? (3)

(A) 1.00

(B) 17.0

(C) 51.0

(D) 153

1.3 Under proper conditions, ammonia, NH3, and oxygen, 02, react to form nitrogen,

N2, and water. How many moles of oxygen would be consumed for each mole of

nitrogen formed? (3)

(A) 0.67

(B) 0.75

(C) 1.5

(0) 3.0

1.4 In a titration, 15.0 cm3 of 0.100 M hydrocholric acid (HCI) neutralizes 30.0 cm3 of

a solution of calcium hydroxide (Ca(OH)2). What is the molarity of the Ca(OH)7_

solution? (3)

(A) 0.0125

(B) 0.0250

(C) 0.0500

(0) 0.200

1.5 in the reaction: mm; 9 H2C03+ cogz'the hydrogen carbonate ion, HCOg' is functioning as (3)

(A) a Bronsted-Lowry acid only.

(B) a Bronsted—Lowry base only.

(C) both a Bronsted-Lowry acid and a Bronsted—Lowry base.

(D) neither a Bronsted-Lowry acid nor a Bronsted-Lowry base.

1.6 Calculate the pH of a solution made by mixing 150 cm3 of 0.10 M NaC2H302 and

250 cm3 of 0.10 M HC2H302. Ka of chHgo2 = 1.8 x 10'5

(Hint: Think of a buffer solution!). (3)

(A) 2.37

(B) 4.52

(C) 4.74

(D) 4.97

1.7 The solubility product constant, Ksp, of Ag3P04 is 1.8 x10'18. What is the molar

solubility of Ag3P04 in water? Neglect any hydrolysis. (3)

(A) 1.5 x 10'5

(B) 8.4 x10‘7

(C) 1.3 x 10'9

(D) 4.5 x 10‘19

1.8 The reaction: 2A(g) + B(g) H 3C(g) + D(g)

is begun with the concentrations ofA and B both at an initial value of 1.00 M.

When equilibrium is reached, the concentration of D is measured and found to

be 0.25 M. The value for the equilibrium constant for this reaction is given by

the expression (3)

(A) [(0.75)3 (0.25)] + [(0.50)2 (0.75)]

(B) [(0.75)3 (0.25)] + [(0.50)2 (0.25)]

(C) [(0.75)3 (0.25)] + [(0.75)2 (0.25)]

(0) [(0.75)3 (0.25)] + [(1.00)2 (1.00)]

1.9 The process of dissolving solid ammonium nitrate (NH4N03) in water is

endothermic. Which statement is true? (3)

(A) The solubility of NH4N03 becomes larger at higher temperatures.

(B) The solubility of NH4N03 becomes lower at higher temperatures.

(C) The solubility of NH4N03 is not affected by temperature.

(D) One cannot predict the solubility behaviour of NH4N03 from the

information given.

1.10 In the oxidation—reduction reaction: Sn4+ + 2Fe2+ 9 2Fe3+ + Sn2+ (3)

(A) Sn4+ is the oxidizing agent and Fe2+ is the reducing agent.

(B) Sn4+ is the reducing agent and Fe2+ is the oxidizing agent.

(C) Sn4+ is the reducing agent and Fe3+ is the oxidizing agent.

(D) Fe3+ is the oxidizing agent and Sn2+ is the reducing agent.

1.11 Consider the unbalanced equation:

_

Fe2+ +_

MnO4' +_

H” --->_

Mn2+ +_

Fe3+ +_

H20

When properly balanced with the simplest set of whole number coefficients,

the sum of the coefficients in the balanced equation is (3)

(A) 12

(B) 18

(C) 22

(D) 24

1.12 When performing an acid-base titration, which procedure would NOT introduce

an error into the experimental results? (3)

(A) adding an unmeasured amount of water to the carefully measured acid

sample which is being titrated.

(B) failing to rinse the burettes with the appropriate reactants after cleaning

and rinsing with water.

(C) failing to remove bubbles of air from the tips of the burettes before

beginning the titration.

(D) using an indicator that changes color at a pH considerably removed from

the pH at the equivalence point of the titration.

1.13 2.80 grams of a monoprotic weak acid, HX, was dissolved in water. Titration of

the acid to its equivalence point required 29.2 mL of 0.500 M NaOH solution.

What is the molecular weight of the acid, HX? (3)

(A) 192 g/mol

(B) 164 g/mol

(C) 96.0 g/mol

(D) 5.21 g/mol

1.14 A standard solution of 0.165 M HCI is being used to determine the concentration

of an unknown NaOH solution. If 25.5 mL of the acid solution are required to

neutralize 15.0 mL of the base, what is the molarity of the NaOH solution? (3)

(A) (0.165) / (25.5 + 15.0) M

(B) (15.0) / (0.165) (25.5) M

(C) (0.165) (15.0 / 25.5) M

(D) (0.165) (25.5/15.0) M

1.15 The indicator ravishing red has a colour change from yellow to red in the pH

range 6.5- 7.5. This indicator would be used to titrate (3)

(A) a weak acid with a strong base

(B) a strong acid with a weak base

(C) a weak acid with a weaker acid

(D) a strong acid with a strong base

Question 2 [10]

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

steels using a potentiometric titration of Cr(V|). Before the titration, samples of the

steel were dissolved in acid and the chromium oxidized to Cr(V|) using peroxydisulfate.

Shown here are the results (as %w/w Cr) for the analysis of a reference steel.

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

2.1 Calculate the mean of the measurements (5 significant figures) (2)

2.2 Calculate the standard deviation (2 significant figures). (2)

2.3 Calculate the 95% confidence interval about the mean. (4)

2.4 What does this confidence interval mean? (2)

Question 3 [10]

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

analysis of Mn“. Each solution contains 25.00 mL (i.e.Vg) ofthe original sample and

either of O; 1.00; 2.00; 3.00; 4.00; or 5.00 mL (Vstd) of a 100.6 mg/L external standard

(CM) of Mn“. All standard addition samples were diluted to 50.00 mL (Vf) before

reading the absorbance. The equation for the calibration curve in the Figure is

55rd = 0.0854 X Vstd + 0.1478

0.60.

0505- y-intercept= MI Vf

0.40 E-

SSDike 0.303-: Vf

0.20 -

0.105-/O: . . . . . . I . . . I . . .

-2.00 0 2.00 4.00 6.00

x-intercept- %

Vfld (MU

Cstd

3.1 What is the concentration of Mn2+ (CA) in this sample? (6)

3.2 Give two reasons why a single-point calibration is not recommended. (4)

Question 4 [10]

The standard reduction potentials for Al3+ and Zn2+ are -1.66 Volt and -0.76 Volt,

respectively.

4.1 Which one of the two redox couples (i.e. Al3+/A|(s) and Zn2+/Zn(s)) will undergo

an oxidation and which one will be reduced if put together?‘

(2)

4.2 Write the corresponding half-reactions. (2)

4.3 Write the overall BALANCED reaction of the system (2)

4.4 How many electrons are involved in the reaction in 4.3? (1)

4.5 Calculate the potential (E) of this reaction. (1)

4.6 Calculate the free energy change (AG in joule) for this reaction. (2)

Question 5 [10]

A 5.00 gram sample of Bad; contaminated with an inert substance is dissolved in

200 mL of water and reacted with an excess of AgNO; solution, precipitating 3.23 g of

AgCl.

5.1 Write the BALANCED reaction leading to the precipitation of AgCl. (2)

5.2 How many moles of BaClz have been used to precipitate 3.23 g of AgCl? (3)

5.3 What was the percentage by mass of BaClz in the original sample? (3)

5.4 What analytical technique has been used here? (2)

9mm [15]

Calculate the pH at the points indicated below if 50.0 mL of 0.100 M aniline

hydrochloride is titrated with 0.185 M NaOH. (Ka for aniline hydrochloride is 2.4 x 10‘5)

C5H5NH3+(aq) + OH_(aq) ---> C5H5NH2(aq) + H20“)

6.1 before the titration begins (4)

6.2 at the midpoint (half-equivalence point) ofthe titration (4)

6.3 after 20 mL of NaOH has been added (7)

END

Data Sheet

I’le t =15 t =———XaXblxwf—wnaxnb[Madam] _

S

J}?! calculated

5dcalculated

poo/ed na + nb

Sim/ed:s§(Na—1)+sfi(Nb—1)+ ........

p=g+t—sNa + Nb + ......

— Nsetsofdala—

J;Confidence

degrees50% 90% 95% 99%

Freedom

1 1'000 6314 12'706 635%Critical Values for the Rejection Quotient

2 0.816 2.920 4.303 9.925

: 2:32: 1:3: 2:23:5 0.727 2.015 2.571 4.032

N 9.0% 9.5% 9_9%6 0.718 1.943 2.447 3.707

Confidence Confidence Confidence

7 0.711 1.895 2.365 3.499 3 0-941 0-970 0-994

8 0.706 1.860 2.306 3.355 4 0.765 0.829 0.926

9 0.703 1.833 2.262 3.250 5 0.642 0_710 0.821

10 0.700 1.812 2.228 3.169

11 0.697 1.796 2.201 3.1066 0'560 0'625 0'740

12 0.695 1.782 2.179 3.0557 0-507 0568 0-680

13 0.694 1.771 2.160 3.012 8 0.468 0.526 0.634

14 0.692 1.761 2.145 2.977 9 0_437 o_493 0.598

15 0.691 1.753 2.131 2.94710 0412 0.466 0568

16 0.690 1.746 2.120 2.921

17 0.689 1.740 2.110 2.898 N = "umber 0“ Observations

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, adenom) 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

co 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'l

= 8.315 kPa dm3 K'1 mol'1

= 8.315 Pa m3 K'1 mol'1

= 8.206 x 10‘2 L atm K'l moI'1

Boltzmann constant k = 1.381 x 10'23J K"1

Planck constant h = 6.626 x 10“] 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 Vm = 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 mp= 1.673 x 10'27 kg

Rest mass of neutron m,, = 1.675 x 10'27 kg

Permitivlty of vacuum 80 = 8.854 x 10'12 C2 J’1 m‘1 (or F m'l)

Gravitational acceleration 9= 9.807 m 5'2

Conversion Factors

1 w = 115‘1

U =0.2390cal=1Nm=1VC

= 1Pam3=1kgmzs'2

1 cal = 4.184]

1 eV = 1.602 x 10491

1 L atm = 101.3 J

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

760 mmHg

1 bar = 1 x 105 Pa

1L =10‘3m3=1dm3

1 Angstrom = 1 x lO'mm = 0.1 nm = 100 pm

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

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

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

10

1.0079 Li6

941

Na 22990

AtomicNumber

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

39.098

40.078

21

22

Sc 44.956

Ti4

7.8823

V 50.942

24

Cr 51.996

54.93826

27

28

Fe

Co

55.847

58933

Ni5869

Cu 63.54630

Zn65.39

31

32

33

34

35

36

GaGeAsSeBrKr 69.723

72.61

74.922

78.96

79.904

83.80

37

Rb85.47

38

Sr8762

39

40

Y 88.906

Zr 91.22441

Nb 92.906

42

95.94

43

Tc(98)

44

45

46

RuRh 101.07

102.91

Pd 10642

Ag 1

07.87

48

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

Cs 132.9156

Ba 137.33

57

72

La 13891

Hf 178.4973

Ta 1

80.95

74

18385

Re1862

76

77

78

Os

Ir

190.2

192.22

Pt 195.08

Au 196.9780

200.59

81

82

83

84

85

86

T1

Pb

Bi

P0

At

Rn

204.38

207.2

208.98

(209)

(210)

(222)

Fr(223)

88

Ra 22603

89

Ac 2270358

Ce 140.1259

Pr 140.91

60

Nd 144.2461

Pm 146.9262

63

64

Sm

Eu

15036

151.97

Gd 157.25

Tb 158.9366

Dy 162.50

68

69

70

71

Ho

Er

Tm

Yb

Lu

164.93

167.26

168.93

173.04

174.97

90

Th 232.0491

Pa 231.0492

U 23803

93

237.0594

95

96

Pu

Am(2444

(234)

Cm(247)

Bk247

98

Cf(251)

1(1)

101

102

103

Es

Fm

Md

N0

Lr

(252)

(257)

(258)

(259)

(260)

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