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Thursday, 25 April 2013

Analytical Chemistry- Model question paper for MSc/PhD in Chemistry

1(a) Distinguish between a specific reaction and a selective reaction. (4 Marks)
(b) Describe the principles of dry ashing and wet digestion of organic and biological materials. Mention some advantages. (6 Marks)
(c) What are determinate and indeterminate errors? (4 Marks)
(d) Calculate the uncertainty in the number of millimoles of chloride contained in 250 ml of a sample when 3 equal aliquots of 25 ml are titrated with AgNO3 with the following results: 36.78, 36.82 and 36.75 ml. The molarity of AgNO3 solution is 0.1167±0.0002 M. (6 Marks)
2(a) What are the common elements of GLP implementation? (4 Marks)
(b) What are the main requirements for validation of electronic records and signatures? (6 Marks)
(c) What are equivalence point and end point of a titration? List the requirements for a titration. (6 Marks)
(d) 500 ml of a 0.1M K2Cr2O7 solution is prepared from a 0.25M solution. What volume of the 0.25M solution must be diluted to 500 ml?
3(a) What is ionic strength? Explain how activity co-efficients are calculated? (6 Marks)
(b) Write a note on Bronsted acid-base theory. (6 Marks)
(c) Explain why boiling the solution near the end point in the titration of sodium carbonate increases the sharpness of the end point. (4 Marks)
(d) Calculate the pH of a solution prepared by mixing 2ml of a strong acid solution of pH 3 and 3ml of strong base of pH 10. (4 Marks)
4(a) Explain the principles of chelation titration indicators. (6 Marks)
(b) What is coprecipitation? Write notes on different types of coprecipitation. (6 Marks)
(c) Explain the principles of adsorption indicators. (4 Marks)
(d) Calculate the solubility of AgIO3 in 0.1M HNO3. Also calculate the equilibrium concentrations of IO3- and HIO3. (4 Marks)
5(a) What is the function of a salt bridge in an electrochemical cell? (4 Marks)
(b) Explain Nicolsky equation. (4 Marks)
(c) Discuss the significance and method of determination of selectivity coefficient. (6 Marks)
(d) Calculate the potential of a solution obtained by reacting 10ml each of 0.2M Fe2+ and 0.2M Ce4+. (6 Marks)
6(a)What effect does complexation have on the voltammetric reduction of a metal ion? (4 Marks)
(b) What are the advantages of an ultramicroelectrode? (4 Marks)
(c) What types of molecular vibration are associated with infrared absorption? (6 Marks)
(d) A compound of formulaweight 280 absorbed 65% of the radiation at a certain wavelength in a 2 cm cell at a concentration of 15 mg/ml. Calculate its molar absorptivity at the wavelength.  (6 Marks)
7(a) Explain why flame emission spectrometry is often as sensitive as atomic absorption spectrophotometry, even though only a small fraction of the atoms may be thermally excited in the flame. (6 Marks)
(b) How does solid-phase extraction differ from solvent extraction? (6 Marks)
(c) How does the Golay equation differ from the van Deemter equation? (4 Marks)
(d) What are the main types of gas chromatography? (4 Marks)
8(a) Describe the factors affecting the selectivity of ion exchange resins. (4 Marks)
(b) Suggest how a Lineweaver-Burk plot can be used to determine whether an inhibitor is competitive or noncompetitive. (6 Marks)
(c) Distingush between discrete and continuous automated devices. (4 Marks)
(d) Mention the principal uses of impingers and scrubbers. What precautions should be taken to protect air samples before analysis? (6 Marks)

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