LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

AD 21

THIRD SEMESTER – NOV 2006

CH 3805 – ANALYTICAL CHEMISTRY – III

 

 

Date & Time : 08-11-2006/9.00-12.00   Dept. No.                                                   Max. : 100 Marks

 

 

 

PART – A

Answer ALL the questions                                                                            ( 10 x 2 = 20 marks)

 

1. How many litres of water can be chlorinated using 1 kg bleaching powder containing 30% available chlorine.  Assume the allowable limit of cl₂ in water is 2 ppm.
2. Can ‘trien’ be used as a titrant to estimate Cu⁺²? Why?
3. How are indicators chosen for redox titration?
4. Compare the solubility of lead iodide in (i) pure H₂O  (ii) 0.1 M aq. KNO₃
   (iii) 0.1 M aq. KI.
5. Define confidence interval.
6. How does potentiometry differ from voltametry.
7. Differentiate electrogravimetry and coulometry.
8. Draw the plot of Emf vs Time for

• Linear sean
• Differential pulse.

1. What is supporting electrolyte?  Explain its role.
2. Define quantum yield.  Account for the high quantum yield of the reaction between H₂ and Cl₂.

 

PART – B

 

Answer any EIGHT questions                                                                       (8 x 5 = 40 marks)

 

1. How will you proceed to collect authentic data from research?
2. Explain the importance of vonweimarnn ratio in gravimetric analysis.
3. Discuss the factors which influence Dpm/Dv in complexometry.
4. describe the salient features of acid base titration in non-aqueous solvents?
5. Show that the equivalence point potential for the titration of Fe⁺² vs MnO in acidic medium is dependent on pH.
6. Draw the titration curve for the titration of 20.00mL of 0.1000 m CH₃COOH vs
   0.0500 m NaOH.  K_a of CH₃COOH is 10^-5.
7. a) How will you determine electrode discharge potential.

1. b) Explain the factors that may affect the nature of electro deposition.

1. Draw a typical cyclic voltagram and indicate i_p(a) , i_p(c), E_p(a) and E_p(c) on the diagram.
2. Explain how polarographic method can be used in quantitative studies.
3. Explain the following briefly
   a) Flame photometry      b) Atomic absorption spectroscopy.
4. Explain the construction and working of hallocathode.
5. How will you prove the liberation of carbon monoxide.  Illustrate with an example.

 

 

 

 

PART – C

 

Answer any FOUR questions                                                                   (4 x 10 = 40 marks)

 

1. Cone common way to determine phosphorus in Urine is to treat the sample, after removing the protein, with molybdenum (VI) and then reduce the resulting
   12-molybdophosphate complex with ascorbic acid to give an intense blue coloured species called molybdenum blue.  The absorbance of molybdenum blue can be measured at 650 nm.  A patient produced 1122 mL of Urine in 24 hours.  A 1.00 mL aliquot of the sample was treated with Mo(VI) and ascorbic acid and was diluted to a volume of
   50.00 ml.  A calibration curve was prepared by treating 1.00 mL aliquots of phosphate standard solutions in the same manner as the urine sample. The absorbances of the standards and the urine sample were obtained at 650 nm and the following results were obtained.

Solution ppm of  P.	Absorbance at 650 nm
1.00	0.230
2.00	0.436
3.00	0.638
4.00	0.848
Urine sample	0.518

Apply the method of least squares to fine the slope, intercept and the standard deviation

of the results Determine the concentration of  P in ppm in Urine sample.

 

1. A 0.3284 g sample of brass (containing Pb, Zn, Cu, Sn,) was dissolved in HNO₃.  The sparingly soluble SnO₂.4H₂O was removed by filtration and the combined filtrated and washings were then diluted to 500.00 mL.  A 10.00 mL aliquot was suitably buffered; titration of the pb, Zn, Cu in this aliquot required 37.56 mL of 0.002500 M EDTA.  The copper in a 25.00 mL  aliquot was masked with tholulfate;  the Pb and Zn were then titrated with 27.60 mL of the EDTA solution.  Cyanide ion was used to mask the Cu and Zn in a 100.00 mL aliquot; 10.80 mL of the EDTA solution was needed to titrate the Pb ion.  Determine the composition of the brass sample;  evaluate the percentage of Sn by difference.

 

1. a) Find out the gravimetric factor if Fe⁺³ is precipitated as Fe(OH)₃ and weighed asFe₂O₃.

1. b) A 0.6407 g sample containing Cl^– and I^– gave silver halide precipitate weighing
   4430 g. This precipitate was than strongly heated in a stream of Cl₂ gas to convert the AgI to Agcl; On completion of this treatment, the precipitate weighted 0.3181 g. Calculate the percentage of Cl^– and I^– in the sample.

 

1. a) Draw a typical polarogram and indicate (i) residual current (ii) limiting current
   (iii)diffusion current on the graph drawing.

1. b) State Ilkovic equation. Explain the terms in it and its applications.

 

1. a) Explain how cyclic voltametry is usefull to determine (i) reversibility
   (ii) Electro chemical stability of a reaction.

1. b) Write a note on chemiluminescence.

1. a) Explain a and differentiate the following  (i) TGA & DTGA  (ii) DSC & DTA

1. b) Calcium oxalate mono hydrate loses H₂O at 100 – 250^o Co (at 400 – 500^oC) and

CO₂ (at 650 – 660^o C) Draw its TGA when 0.25 g is heated to 700^oC at fixed

Atmosphere.

 

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