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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:2012

INSTRUCTIONS
Answer ALL questions.
Q1. a) State the law of photometry and explain the causes of non-linearity of the law at high
concentration when used for quantitative analysis in UV-Visible spectrometry.
[8 marks]
b) Flame atomic absorption spectroscopy is a popular technique for the determination of
elements.
(i) Using sodium chloride, describe the atomization process taking place in the
flame.
(ii) Discuss the chemical interferences experienced and how they can be minimized.
(iii) What are the advantages of using an electro-thermal procedure as compared to
flame procedure? [12 marks]
c) Using a diagram, explain the difference between single-beam and double-beam
spectrophotometers. [5 marks]
Q2. a) Explain the differences between the following terms:
(i) chemical shift and spin-spin splitting in NMR
(ii) DTA and DSC in thermoanalysis
(iii) Chemical ionization and electron impact ionization in MS
(iv) Liquid and solid state membranes in ion selective electrodes. [16 marks]
Page 2 of 2
b) (i) Explain what causes the absorption of radiation by molecule in the
mid-infrared (IR) region of the electromagnetic spectrum.
(ii) Describe the nature of the IR spectrum obtained for CO2.
(iii) Explain the process if identifying a compound using IR. [10 marks]
Q3. a) Describe, with aid of a diagram how a photomultiplier tube detector works.
[7 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 carried out.
(iii) 10mg of a labeled analyte, with specific activity of 18870cpm was added to the
Mixture analysed. After thorough mixing, 1.5mg of the pure analyte was separated and its specific activity was found to be 1550cpm. What was the amount of the analyte in the original sample?

Sch 404: Instrumental Methods Question Paper

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