LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
M.Sc. DEGREE EXAMINATION – CHEMISTRY
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FIRST SEMESTER – April 2009
CH 1809 / CH 3805 – ANALYTICAL CHEMISTRY
Date & Time: 30/04/2009 / 1:00 – 4:00 Dept. No. Max. : 100 Marks
PART A
Answer all the questions. 10 x 2 = 20
- Round each of the following numbers to four and three significant figures
- a) 28755 b) 0.002045
- Five determinations of vitamin C content of citrus fruit gave the following results:
0.218, 0.219, 0.230, 0.215 and 0.220 mg/ml. Apply the Q-test to see if 0.230 value can be discarded? (Q table = 0.64)
- How are the samples derivatised in gas chromatography?
- What are the factors affecting the flame temperature of the burners in flame spectrometry?
- What is the principle of atomic absorption spectroscopy?
- Differentiate the formality of a solution from molarity with an example.
- Acetic acid has autoprotolysis constant of 3.55 x 10-15. Calculate the pH of pure acetic acid.
- Calculate the ionic strength of a solution obtained by mixing 50 ml o f 0.01M sodium perchlorate and 50 ml of 0.01M lanthanum(III) perchlorate.
- Mention the significance of selectivity coefficient in ion selective electrode.
- What are the advantages of dropping mercury electrode?
PART B
Answer any eight questions. 8 x 5 = 40
- Write short notes on chemical interferences in flame emission spectroscopy?
- What are the different types of pumps used in HPCL? Explain.
- How is the purity of pharmaceuticals determined by DSC?
- Explain the advantages and disadvantages of using premix and total consumption burners used in AAS.
- How is sulphate determined by turbidimetry?
- Discuss the fluorimetric determination of quinine.
- 50 ml of sample of a sugar substitute containing amino acids as the active ingredient was dissolved in 25 ml of 0.02M perchloric acid in glacial acetic acid as the solvent. The excess acid required 14.62 ml of 0.01M potassium acetate for titration using methyl violet as indicator. If the molecular mass of the amino acid mixture is 90. Calculate its percentage by weight. Also express it in terms of ppm.
- Derive an expression for equivalence point potential for the redox reaction between MnO4- and Fe2+ in acid medium.
- Explain the effect of i) complexation, ii) adding an indifferent electrolyte as the solubility of a sparingly soluble salt with suitable example for each.
- What is the origin of polarographic maxima? Explain.
- 50 ml of 0.1M H2A is titrated with 0.1M KOH. Calculate the pH after adding 50 ml of NaOH. K1 = 10-5 and k2 = 10-8. Derive the relevant relation.
- How is Sb3+ estimated using coulometry?
PART C
Answer any four questions. 4 x 10 = 40
- Explain the principle and instrumentation of capillary electrophoresis.
- a) Draw and explain the thermal decomposition of CuSO4.5H2O by TGA and
DTA studies.
- b) Discuss the various types of detectors used in GC. (5+5)
- What are spectrophotometric titrations? Explain the types with the advantages.
- Explain any two of the following:
- a) principle of cyclic voltammetry
- b) solid state ion selective electrodes
- c) non-aqueous titrations
- d) Ilkovic equation
- 0.2767g sample of an alloy containing principally iron and zinc is dissolved in acid and diluted to 500 ml (solution A). The pH of a 50 ml aliquot of A is adjusted to 1 and the iron is titrated with 32 ml of 0.0125M EDTA. The pH is then adjusted 10 and titrated with 6.4 ml of the same EDTA. Calculate the percentage of Fe and Zn in the sample. Also explain the significance of controlling pH in EDTA titrations. (5+5)
- a) 25 ml of 0.1M KBr is treated with 0.2 M AgNO3 solution. Calculate the pAg after adding i) 5, ii) 12.5, iii) 15 ml of 0.2 M AgNO3. Ksp for AgBr is 5 x 10-13.
- b) What is the principle of Volhard’ method? (6+4)
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