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Sch 404: Instrumental Methods Question Paper

Sch 404: Instrumental Methods

Course:Bachelor Of Science

Institution: Kenyatta University question papers

Exam Year:2011

INSTRUCTIONS: Answer ALL questions
Q1
a) Molecular spectroscopy involves absorption and emission of energy involving electronic, vibrational and rotational electron transitions. Using a diagram explain the changes in energy and the resulting techniques.
[4 marks]
b) Quantitative analysis using UV/Visible spectrophotometric analysis is based on Lambert-Beer’s Law.
(i) State the law and explain why the law fails to work at high concentrations.
(ii) A compound has a molar absorptivity of 2.1 x 103 L/cm/mol. What concentration of the compound would be required to produce a solution with a transmittance of 8.42% in a 2.50cm cell?
[7 marks]
c) A water quality chemist determined the levels of calcium in well water
using flame atomic absorption spectroscopy.
(i) Explain the principle of analysis used in the technique.
(ii) Describe the process of atomization involved in the technique.
(iii) Discuss the chemical interferences experienced and how they can be minimized.
Page 2 of 2
(iv) What are the advantages of using an electrothermal atomization procedure as compared to the flame procedure?
[16 marks]
Q2
a) Infrared (IR) spectroscopy is used to determine the structure of molecules based
on its vibrations and rotations.
(i) Using example, explain the type of vibrations that are IR active.
(ii) Discuss the various vibrations in a molecule and how they are used to identify the structure of a molecule.
[6 marks)
b) Describe the following terms used in NMR
(i) Chemical shift
(ii) Spin-spin splitting
(i) Screening constant
(ii) Internal standard
[8 marks]
c) (i) Describe the modes of separation used in column chromatography.
(ii) Discuss the similarities and differences of GC and HPLC columns.
[6 marks]
Q3 a) (i) Draw a polarogram and explain its main features.
(ii) State the advantages of using a dropping mercury electrode in polarography
[6 marks]
b) Analysis in radiochemical techniques depends upon the radioactivity of the solute.
(i) Name the particles/radiation emitted from radionuclides.
(ii) Explain how activation analysis is used in quantitative analysis.
[6 marks]
c) Write short notes to differentiate the following terms
(iii) Solid state electrode (GSE) and liquid state electrode
(iv) Differential thermal analysis (DTA) and differential scanning calorimetry (DSC)
(v) Electron impact (EI) ionization and chemical ionization (CI) in MS
[12 marks]

Sch 404: Instrumental Methods Question Paper

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