CEE 572

4 November 1999

Mid-term Exam

 

Open book, open notes

Answer all three (3) sets of questions:

 

I. (20%) Place the letter of the piece of laboratory glassware, equipment or apparatus that would be used for the following in the appropriate box:

 

1

Container for weighing 0.1 mg of a chemical

 

2

Vessel for holding solution being titrated

 

3

Measurement of exactly 1 liter

 

4

Vessel for dissolving a solid to make 1 liter of solution

 

5

Measurement of exactly 1 mL

 

6

Fast measurement of 42.5 mL

 

7

Addition of a titrant during volumetric analysis

 

8

Comparison of standard with sample based on a gravimetric analytical procedure

 

9

Separation of dissolved from particulate

 

10

Storage of a volatile or corrosive sample

 

 

A.           beaker with graduations

B.           volumetric flask

C.           buret

D.           pipet

E.           pipet bulb

F.           Erlenmeyer flask

G.           evaporating dish

H.           weighing paper

I.            weighting tray

J.            analytical balance

K.           spectrophotometer

L.           glass-stoppered reagent bottle

M.          glass fiber filter

N.           buret stand

O.           vacuum pump

P.           graduated cylinder

Q.           Incubator

R.           Filter flask

 

 

 

II. (45%) Answer either  II.A. or II.B.

 

          II. A. You've just prepared a solution by dissolving 20 mg ammonium nitrate (NH4NO3), and 30 mg magnesium nitrate dihydrate (Mg(NO3)22H2O) in 1 Liter of distilled water.

 

1. What is the theoretical TDS of this solution?

2. What is the concentration of nitrate-nitrogen (i.e., NO3-N) in this solution in mg/L?

3. What is the concentration of total nitrogen in this solution in mg/L?

4. Calculate the expected specific conductance of this solution based on ideal behavior (i.e., no effect of ionic strength).

 

            II.B. A river water was analyzed 4 times for alkalinity.  Sample volumes of 100 mL were titrated with 0.01N HCl.  Titrant volumes (mL) to reach the phenolphthalein and methyl orange endpoints are as follows:

 

 

Titrant Volume

Sample #

Vph

Vmo

1

6.0

22.6

2

5.6

21.5

3

5.8

20.4

4

6.3

20.9

 

               1. What is the best estimate for the:

                           a. total alkalinity in mg/L as CaCO3?

                           b. carbonate alkalinity in mg/L as CaCO3?

                           c. bicarbonate alkalinity in mg/L as CaCO3?

d. hydroxide alkalinity in mg/L as CaCO3?

2. What is the 95% confidence interval for the estimate of total alkalinity?

 

 

 

 

 

III. (35%) You've just completed a solids analysis of a sample from the Amherst Wastewater Treatment Plant's activated sludge unit.  Given the following raw data, calculate:

 

               a. the mean VSS concentration

               b. the 95% confidence interval for this mean.

 

 

 

Sub Sample

 

  #1

  #2

  #3

 #4

Pan & Filter alone (grams)

1.2355

1.3569

1.3231

1.3125

Pan & Filter + residue dried to 103ēC (grams)

1.2701

1.3934

1.3490

1.3490

Pan & Filter + residue dried to 550ēC (grams)

1.2630

1.3896

1.3464

1.3394

Original sample volume (mL)

10

12.5

8.8

13.1

 

Properties of the Stable Elements[1]

Element

Symbol

Atomic #

Atomic Wt.

Valence

Electronegativity

Aluminum

Al

13

 26.98

3

1.47

Antimony

Sb

51

121.75

3,5

1.82

Argon

Ar

18

 39.95

0

 

Arsenic

As

33

 74.92

3,5

2.20

Barium

Ba

56

137.34

2

0.97

Beryllium

Be

 4

  9.01

2

1.47

Bismuth

Bi

83

208.98

3,5

1.67

Boron

B

 5

 10.81

3

2.01

Bromine

Br

35

 79.91

1,3,5,7

2.74

Cadmium

Cd

48

112.40

2

1.46

Calcium

Ca

20

 40.08

2

1.04

Carbon

C

 6

 12.01

2,4

2.50

Cerium

Ce

58

140.12

3,4

1.06

Cesium

Cs

55

132.91

1

0.86

Chlorine

Cl

17

 35.45

1,3,5,7

2.83

Chromium

Cr

24

 52.00

2,3,6

1.56

Cobalt  

Co

27

 58.93

2,3

1.70

Copper 

Cu

29

 63.54

1,2

1.75

Dysprosium

Cy

66

162.50

3

1.10

Erbium 

Er

68

167.26

3

1.11

Europium

Eu

63

151.96

2,3

1.01

Fluorine

F

 9

 19.00

1

4.10

Gadolinium

Gd

64

157.25

3

1.11

Gallium 

Ga

31

 69.72

2,3

1.82

Germanium

Ge

32

 72.59

4

2.02

Gold    

Au

79

196.97

1,3

1.42

Hafnium 

Hf

72

178.49

4

1.23

Helium 

He

 2

  4.00

0

 

Holmiuum

Ho

67

164.93

3

1.10

Hydrogen

H

 1

  1.01

1

2.20

Indium 

In

49

114.82

3

1.49

Iodine 

I

53

126.90

1,3,5,7

2.21

Iron     

Fe

26

 55.85

2,3

1.64

Krypton 

Kr

36

 83.80

0

 

Lanthanium

La

57

138.91

3

1.08

Lead    

Pb

82

207.19

2,4

1.55

Lithium  

Li

 3

  6.94

1

0.97

Lutetium

Lu

71

174.97

3

1.14

Magnesium

Mg

12

 24.31

2

1.23

Manganese

Mn

25

 54.94

2,3,4,6,7

1.60

Properties of the Stable Elements

 

Element

Symbol

Atomic #

Atomic Wt.

Valence

Electronegativity

Mercury 

Hg

80

200.59

1,2

1.44

Molybdenum

Mo

42

 95.94

3,4,6

1.30

Neodymium

Nd

60

144.24

3

1.30

Neon

Ne

10

 20.18

0

1.07

Nickel  

Ni

28

 58.71

2,3

1.75

Niobium 

Nb

41

 92.91

3,5

1.23

Nitrogen

N

 7

 14.01

3,5

3.07

Osmium  

Os

76

190.2

2,3,4,8

1.52

Oxygen  

O

 8

16.00

2

3.50

Palladium

Pd

46

106.4

2,4,6

1.39

Phosphorus

P

15

 30.97

3,5

2.06

Platinum

Pt

78

195.09

2,4

1.44

Potassium

K

19

 39.10

1

0.91

Praseodymium

Pr

59

140.91

3

1.07

Rhenium  

Re

75

186.2

 

1.46

Rhodium   

Rh

45

102.91

3

1.45

Rubidium

Rb

37

 85.47

1

0.89

Ruthenium

Ru

44

101.07

3,4,6,8

1.42

Samarium

Sm

62

150.35

2,3

1.07

Scandium

Sc

21

 44.96

3

1.20

Selenium

Se

34

 78.96

2,4,6

2.48

Silicon 

Si

14

 28.09

4

1.74

Silver 

Ag

47

107.87

1

1.42

Sodium  

Na

11

 22.99

1

1.01

Strontium

Sr

38

 87.62

2

0.99

Sulfur  

S

16

 32.06

2,4,6

2.44

Tantalum

Ta

73

180.95

5

1.33

Tellurium

Te

52

127.60

2,4,6

2.01

Terbium  

Tb

65

158.92

3

1.10

Thallium

Tl

81

204.37

1,3

1.44

Thorium  

Th

90

232.04

4

1.11

Thulium  

Tm

69

168.93

3

1.11

Tin    

Sn  

50

118.69

2,4

1.72

Titanium

Ti

22

 47.90

3,4

1.32

Tungsten

W

74

183.85

6

1.40

Uranium  

U

92

238.03

4,6

1.22

Vanadium

V

23

 50.94

3,5

1.45

Xenon  

Xe

54

131.30

0

 

Ytterbium

Y

39

 88.91

2,3

1.06

Zinc   

Zn

30

 65.37

2

1.66

Zirconium

Zr

40

 91.22

4

1.22

 

 

 

 

Ionic Conductances, mho-cm2/equivalent

(I=0, 25oC)

 

Cation

Anion

H+

349.8

OH-

198.0

Na+

50.1

HCO3-

44.5

K+

73.5

F-

55.4

Li+

38.7

Cl-

76.3

NH4+

73.4

Br-

78.4

Ca+2

59.5

CH3COO-

40.9

Mg+2

53.1

NO3-

71.4

 

 

SO4-2

79.8

 

 

 

 

Student's t Distribution

 

Degrees of

Alpha Values

Freedom

10%

5%

2.5%

1%

0.5%

   1

3.078

6.314

12.706

31.821

63.657

   2

1.886

2.920

4.303

6.965

9.925

   3

1.638

2.353

3.182

4.541

5.841

   4

1.533

2.132

2.776

3.747

4.604

   5

1.476

2.015

2.571

3.365

4.032

   6

1.440

1.943

2.447

3.143

3.707

   7

1.415

1.895

2.365

2.998

3.499

   8

1.397

1.860

2.306

2.896

3.355

   9

1.383

1.833

2.262

2.821

3.250

  10

1.372

1.812

2.228

2.764

3.169

  15

1.341

1.753

2.131

2.602

2.947

  20

1.325

1.725

2.086

2.528

2.845

 inf.

1.282

1.645

1.960

2.326

2.576

 

 

 

Calculating Quotients for Dixon's Test

 

# Observations

Statistic

Test for High Value, Xn

Test for Low Value, X1

    3-7

Q10

(Xn-Xn-1)/(Xn-X1)

(X2-X1)/(Xn-X1) 

    8-10

Q11

(Xn-Xn-1)/(Xn-X2)

(X2-X1)/(Xn-1-X1)

   11-13

Q21

(Xn-Xn-2)/(Xn-X2)

(X3-X1)/(Xn-1-X1)

   14-25

Q22

(Xn-Xn-2)/(Xn-X3)

(X3-X1)/(Xn-2-X1)

 

 

 

 

Values for Dixon's Quotient, Qs

 

 

 

Risk of False Rejection

Statistic

# Observations

0.5%

1%

5%

10% 

Q10

3

0.994

0.988

0.941

0.886

 

4

0.926

0.889

0.765

0.697

 

5

0.821

0.780

0.642

0.557

 

6

0.740

0.698

0.560

0.482

 

7

0.680

0.637

0.507

0.434

Q11

8

0.725

0.683

0.554

0.479

 

9

0.677

0.635

0.512

0.441

 

10

0.639

0.597

0.477

0.409

Q21

11

0.713

0.679

0.576

0.517

 

12

0.675

0.642

0.546

0.490

 

13

0.649

0.615

0.521

0.467

Q22

14

0.674

0.641

0.546

0.492

 

15

0.647

0.616

0.525

0.472

 

 16

0.624

0.595

0.507

0.454

 

 17

0.605

0.577

0.490

0.438

 

 18

0.589

0.561

0.475

0.424

 

 19

0.575

0.547

0.462

0.412

 

20

0.562

0.535

0.450

0.401

 

 

 

 


[1]from; The Chemists Companion: A Handbook of Practical Data, Techniques and References. A.J. Gordon & R.A. Ford, J. Wiley & Sons Publ., New York, 1972.