Bài tập phần phân tích trắc quang và phổ nguyên tử

Compare IR light with UV light in terms of wavelength, frequency, and wavenumber?. Explain briefly the phenomenon of light absorption in terms of the energy associated with light and in t

BÀI TẬP PHẦN PHÂN TÍCH TRẮC QUANG VÀ PHỔ NGUYÊN TỬ

Phần 1: sách “Quantitative Chemical Analysis” của Daniel Harris.

Chương 17: Fundamentals of Spectroscopy

✔ Phần Exercises: Các bài 17A, B,C, D, E

✔ Phần Problems: các bài 17.2 đến 17.12; 17.16 đến 17.19

Chương 18: Spectrophotometers

✔ Phần Exercises: Các bài 18A, B,C, D

✔ Phần Problems: các bài 18.1; 18.2; 18.6

Chương 20: Atomic Spectrometry

✔ Phần Exercises: Các bài 20A, B,C, D

✔ Phần Problems: các bài 20.1; 20.2; 20.4

Phần 2:

1 What is meant by the “dual nature” of light?

2 Which has a greater frequency, light of wavelength 627 Å

or light of wavelength 462 nm?

3 Which has the longer wavelength, light with a frequency of 7.84 × 1013 s–1 or light with a frequency of 5.13 × 1013 s–1?

4 Which has the greater energy, light of wavelength 591 nm

or light with a wavelength of 238 nm?

5 Which has the greater wavenumber, light with an energy of 7.34 × 10–13 J or light with an energy of 5.23 × 10–14 J?

6 Which has the lower energy, light with a wavenumber of 1.7 × 103 cm–1 or light with a wavenumber of 1.91 × 104

cm–1?

7 If the wavelength used in an instrument is changed from

460 to 560 nm,

(a) Has the energy been increased or decreased?

(b) Has the frequency been increased or decreased?

(c) Has the wavenumber been increased or decreased?

8 Compare IR light with UV light in terms of wavelength, frequency, and wavenumber

9 What are the upper and lower wavelength limits of visible light?

10 Compare infrared and ultraviolet radiation,

(a) In terms of energy?

(b) In terms of the type of disturbance they cause within molecules?

11 Why does a yellow sweatshirt appear yellow and not some other color?

12 What is an energy level diagram? What is meant by

“ground state?” What is meant by “excited state?”

13 Explain briefly the phenomenon of light absorption in terms of the energy associated with light and in terms of electrons and the energy levels in atoms and molecules

14 What is meant by each of the following: electronic transition, vibrational transition, rotational transition?

Which of these transitions requires the most energy? Which requires the least energy?

15 Describe the basic instrument for measuring light

absorption

16 Distinguish among UV/VIS spectrophotometry, and atomic spectroscopy

17 What is an “absorption spectrum?” What is the

difference between a molecular absorption spectrum and an atomic absorption spectrum, and why does this difference exist?

18 What is a line spectrum? Why is an atomic absorption spectrum a “line” spectrum?

19 Why is it that with atoms, only certain specifc

wavelengths get absorbed (resulting in a line spectra),

whereas with molecules, broad bands of wavelengths get absorbed (resulting in continuous spectra)?

20 What is a “transmission spectrum?” What is an

“emission spectrum?”

21 Differentiate between an energy level diagram used to depict atomic absorption from one used to depict atomic emission

22 What is the mathematical defnition of transmittance, T? Defne the parameters that are found in this

mathematical defnition

23 What absorbance corresponds to a transmittance of (a) 0.821?

(b) 0.492?

(c) 0.244?

24 What absorbance corresponds to a percent

transmittance of

(a) 46.7% T?

(b) 28.9% T?

(c) 68.2% T?

25 What transmittance corresponds to an absorbance of (a) 0.622?

(b) 0.333?

(c) 0.502?

26 What is the percent transmittance, given that the absorbance is

(a) 0.391?

(b) 0.883?

(c) 0.490?

27 What is Beer’s law? With one word each, tell what each of the parameters is

40 What is the absorbance given that the absorptivity is 2.30 × 104 L mol–1 cm–1, the pathlength is 1.00 cm, and the concentration is 0.0000453 M?

28 A sample in a 1-cm cuvette gives an absorbance

reading of 0.558 If the absorptivity for this sample is

15,000 L mol–1 cm–1, what is the molar concentration?

29 The transmittance of a solution, measured at 590 nm

in a 1.5-cm cuvette was 76.2%

(a) What is the corresponding absorbance?

(b) If the concentration is 0.0802 M, what is the

absorptivity of this species at this wavelength?

(c) If the absorptivity is 10,000 L mol–1 cm–1, what is the concentration?

30 Calculate the transmittance of a solution in a 1.00-cm cuvette given that the absorbance is 0.398 What additional information, if any, would you need to calculate the molar absorptivity of this analyte?

31 What is the molar absorptivity given that the

absorbance is 0.619, the pathlength is 1.0 cm, and the

concentration is 4.23 × 10–6 M?

32 Calculate the concentration of an analyte in a solution given that the measured absorbance is 0.592, the pathlength

is 1.00 cm, and the absorptivity is 3.22 × 104 L mol–1 cm–1

33 What is the concentration of an analyte given that the

%T is 70.3%, the pathlength is 1.0 cm, and the molar

absorptivity is 8382 L mol–1 cm–1?

34 What is the pathlength in cm when the molar

absorptivity for a given absorbing species is 1.32 × 103 L

mol–1 cm–1, the concentration is 9.23 × 10–4 M, and the

absorbance is 0.493?

35 What is the pathlength in cm when the transmittance is 0.692, the molar absorptivity is 7.39 × 104 L mol–1 cm–1, and the concentration is 9.23 × 10–5 M?

36 What is the transmittance when the molar absorptivity for a given absorbing species is 2.81 ×102 L mol–1 cm–1, the pathlength is 1.00 cm, and the concentration is 1.87 × 10–4

M?

37 What is the molar absorptivity when the percent

transmittance is 56.2%, the pathlength is 2.00 cm, and the concentration is 7.48 × 10–5 M?

38 In each of the following, enough data are given to calculate the indicated parameter(s)

Show your work

(a) Calculate “A” given that “T” is 0.551

(b) Calculate the molar absorptivity given that “A” is

0.294, “b” is 1.00 cm, and “c” is 0.0000351 M

(c) Calculate the transmittance given that the absorbance is 0.297

(d) Calculate T given that %T is 42.8%

(e) Calculate the percent transmittance, given that the

absorptivity is 12562 L mol–1 cm–1, the pathlength is 1.00

cm, and the concentration is 3.55 × 10–6 M

39 In each of the following, enough data are given to calculate the indicated parameter(s)

(a) Calculate “A” if “T” is 0.651

(b) Calculate “a” if “A” is 0.234, “b” is 1.00 cm, and “c” is 0.0000391 M

(c) Calculate T if A is 0.197

(d) Calculate T if %T is 62.8%

(e) Calculate %T if a is 13562 L mol–1 cm–1, b is 1.00 cm, and c is 3.55 × 10–6 M

40 A standard 5-ppm iron sample gave a transmittance reading of 52.8% What is the concentration of an unknown iron sample if its transmittance is 61.7%?

41 A series of fve standard copper solutions is prepared, and the absorbances measured as indicated below Plot the data and determine the concentration of the unknown

42 Compare the common sample containers for UV/VIS work, and atomic absorption work

43 State the importance of the wavelength of maximum absorbance

44 Draw a diagram showing all the components of a basic spectrophotometer

45 Defne colorimeter, UV spectrophotometer, and UV-Vis spectrophotometer.

46 Briefly describe the light sources used for both visible and UV work

47 There is no monochromator placed between the light source and the flame in an AA experiment Why is this?

48 The hollow cathode lamp must contain the metal to be analyzed in the cathode Explain

49 What is a nebulizer? Describe its use in conjunction with a premix burner

50 Describe the design and use of the premix burner in flame AA

51 What purpose does the light chopper serve in an AA instrument?

52 How does a single-beam atomic absorption instrument differ from a double-beam instrument? What advantages does one offer over the other?

53 How does a double-beam atomic instrument differ from a double-beam molecular instrument?

54 Does Beer’s law apply in the case of flame AA?

Explain

55 What is the standard additions method and why does it help with the problem of chemical interferences?

56 What are two disadvantages of the standard additions method?

57 Give a brief description of the graphite furnace

method of atomization

58 Describe exactly how the atomic vapor is produced in

a graphite furnace

59 What is the difference in the optical path of graphite furnace AA and flame AA?

60 The graphite furnace assembly utilizes argon gas, cold water, and a source of high voltage Explain

61 Describe the temperature program applied to a

graphite furnace and explain each of the processes

involved

62 Why must the graphite furnace be protected from air?

63 Why is the absorbance signal developed in the case of the graphite furnace AA technique said to be “transient”?

64 What are the advantages and disadvantages of the graphite furnace atomizer?

65 What do the letters ICP stand for? Is the ICP technique more closely related to AA or flame photometry? Explain

66 Describe the ICP analysis method in detail

67 What are the advantages of the ICP technique?

68 What are the advantages of the following atomic

techniques over the standard flame atomic absorption?

(a) Graphite furnace AA

(b) ICP

69 Why is the cold vapor mercury technique good only for mercury?

70 Describe the hydride generation technique Why is it useful?