Loyola College Supplementary Chemistry April 2006 Analytical Chemistry – III Question Paper PDF Download

 

             LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

SUPPLEMENTARY SEMESTER EXAMINATION – JUN 2006

M.Sc. DEGREE EXAMINATION

                                                 CH 3805 – ANALYTICAL CHEMISTRY – III

 

 

 

Date & Time : 26/06/2006/9.00 – 12.00        Dept. No.                                                       Max. : 100 Marks

 

PART – A

Answer ALL the questions.                                                 10 x 2 = 20 marks

  1. Mention the characteristics of a good set of Measurements.
  2. A chloride sample containing bromide as contaminant is estimated by argentometric titration.  What is the error associated with the result?
  3. Calculate the pH of the mixture containing 20.00mL of 0.0250M CH3COOH and 40.00mL of 0.0125M OH.  Ka  for CH3COOH is 10–5.
  4. A little of Mg EDTA  complex is added in the estimation of Ca+2 using EDTA.  Why?
  5. What is the gravimetric factor for Fe+3, when it is precipitated as ferric hydroxide and weighed as ferric oxide?
  6. Calculate the current required to deposit all the metal ions in 100 ml of 0.01M Cu2Cl2 in 30 minutes.
  7. What is the difference between potentiometry and voltametry?
  8. Explain why electroylysis of aqueous 1 M NaCl results in the liberation of hydrogen and not Na?
  9. Explain the principle of AAS method of estimation of metal ions.
  10. Mention any two applications of TGA.

PART – B

 

Answer any EIGHT questions.                                                        8 x 5 = 40 marks

  1. Compare the solubility of Mg(OH)2 (Ksp Mg(OH)2 = 10–12 mol3dm–9) in
    i) 10–2M La2(SO4)3                              ii) 10–2M AlCl3.
  2. Analysis of Vitamin C content of a citrus fruit drink gave the following results.  0.218, 0.219, 0.215, 0.230 and 0.220 mg/mL.  Calculate the 99% confidence interval if t99% is 4.60.
  3. Write a note on the acid base titration in non-aqueous solvent.
  4. Discuss the factors which affect  ate the equivalence point.
  5. Compare the initial equivalence point pH for the following.
    i) 20.00mL of 10–2M, CH­3COOH Vs 10–2M OH
    ii) 20.00 mL of 10–2 CHCl2COOH Vs 10–2M OH–‑.
    Ka for CH3COOH is 10–5 and Ka for CHCl2 COOH is 10–2.
  6. Show that the equivalence point potential for Fe+2 Vs MnO4–‑/H+ depends on pH.
  7. Define half wave potential.  How does it differ from standard reduction potential?
  8. An aqueous solution of CdSO4 was analysed at its half-wave potential with a current of 0.6 A.  Calculate the time required to lower the concentration of 10ml of Cd2+ solution from 2 x 10–4 M to 1.9 x 10–4M.  What conclusion you can draw from the result?
  9. Explain a coulometric method of estimation thiosulphate using iodide.
  10. How will you estimate bromide by ampereometric titration?
  11. Explain, with suitable diagrams, the difference between TGA and DTA.
  12. Explain, with an example, the principle of i) steam distillation and ii) solvent extraction.

PART – C

 

Answer ALL the questions.                                                 10 x 2 = 20 marks

  1. The following data were obtained in calibrating a calcium ion electrode for the determination of pCa.  A linear relationship between the potential E and pCa is known to exist.

pCa                  E mv

5.00                 –53.8

4.00                 –27.7

3.00                 +2.7

2.00                 +31.9

1.00                 +65.1

  1. i) Calculate the equation for the best straight line through these points.
  2. ii) Obtain the pCa of a serum solution in which the electrode potential is 20.3mV, which is the mean of four measurements.

iii) Also calculate the standard deviation of the slope and the result.

  1. Draw the titration curve for the titration of 20.00mL of 0.0250M Ni+2 vs 0.01250M EDTA at pH 8 by finding out the pNi at the following stages: i) initial ii) pre-equivalence point iii) just before equivalence point  iv) the equivalence point v) post equivalence point.
    Keff for [Ni EDTA]–2 is 1016 at pH 8.
  2. i) Determine the concentration of all the species in the mixture containing 50 mL of 0.0500M Fe+2 and 25mL of 0.1000M Ce+4 in 1.000M H2SO4. E0Ce+4/Ce+3 = 1.5V; E0Fe+3 /Fe+2 = 0.70V
  3. ii) A 0.6200g sample containing NaCl and NaBr gives 0.5120g precipitate of silver halide. Another 0.6200g sample containing NaCl and NaBr gives 0.5120g precipitate of silver halide.  Another 0.6200g sample is titrated with 0.1070M AgNO3 requiring 28.10mL.  Calculate the percentages of NaCl and NaBr in the sample.

 

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Loyola College M.Sc. Chemistry April 2006 Analytical Chemistry-III Question Paper PDF Download

             LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – APRIL 2006

                                                 CH 3805 – ANALYTICAL CHEMISTRY – III

 

 

Date & Time : 18-04-2006/AFTERNOON   Dept. No.                                                       Max. : 100 Marks

PartA (20 Marks)

Answer ALL questions (10 x 2 = 20)

  1. How large a sample to be taken for analysis using a chemical balance so that the maximum relative uncertainty in the sample weight is 5 ppm?
  2. Explain replacement titration with an example.
  3. Compute the equivalent point potential for titration of
    A2+ vs B4+ (SRP: B4+ / B2+ = 1.44 V ;  A4+ / A2+ = 0.15V )
  4. How is an indicator chosen for a red ox titration?
  5.  Calculate the equilibrium constant for the following reaction:

HCN + OH   ⇌  CN + H2O; Ka (HCN) = 1 x 10 -10

  1. How does coulometer differ from potentiometric technique?
  2. Explain how the addition of nitrate ion avoids the liberation of hydrogen?
  3. State an expression for the residual current and explain the terms in it.
  4. Explain the effect of added CN on the electrode deposition of Ag.
  5. Mention any two applications of DTA.

 

PartB (40 Marks)

 

Answer any EIGHT questions (8 x 5 = 40)

  1. Show that the equivalence point for the titration of Fe2+ vs MnO4is pH dependant.
  2. Explain diverse ion effect
  3. Draw  the titration curves for the follwing:
  • 20 mL of 0.1 M NaOH vs 0.1M CH3COOH
  • 20 mL of 0.1 M NaOH vs 0.1M H2SO4.
  1. Write a note on homogeneous precipitation.
  2. Exactly 0.3525 g of 96.5% Na2SO4 required 37.7 mL of a solution of BaCl2. Calculate the concentration and express the concentration of BaCl2 in scientific notation.
  3. The values of Ka1, Ka2, Ka3 & Ka4 for EDTA (H4Y) are 1x 10-2 , 1x 10-3 , 1x 10-8  & 1x 10-12 ,  respectively. Calculate the conditional stability constant for the following process in 1x 10-2 M HCl.

Fe3+ + Y4-     ⇌       FeY–     ; Kobs = 1 x 1025

    1. How will you estimate Cu2+ by electro gravimetric method?

 

  1. Draw a typical polarogram and indicate the following on the diagram.
  1. Residual current.
  2. Limiting current
  3. Diffusion current
  4. How are they related to each other?
  1. A certain Pb2+ solution gives id = 1.00 mA . To 10 ml of the solution 0.5 ml of 0.04 M of Pb2+ was added. The id of the solution was found to be 1.5 mA. Calculate the concentration of Pb2+ in the unknown solution.
  2. Draw and explain the ampereometric titration curves for the following titrations if the applied potential is maintained at half wave potential of Pb2+
  1. Pb2+ vs CrO42- b . CrO42- vs Pb2+
  1. Explain how the cyclic voltometric technique can be used to determine the electrochemical reversibility and stability of a red-ox  system.
  2. Explain the following with an example.

(i) Fluorimetric estimation of metal ions

(ii) Chemiluminescence

 

Part-C (40 Marks)

 

Answer any FOUR questions (4 x 10 = 40)

  1. The following are peak areas for chromatogram of standard solutions of methyl vinyl ketone (MVK)
Conc. MVK

mmol-1

Relative peak Area
0.500 3.76
1.50 9.16
2.50 15.03
3.50 20.42
4.50 25.33
5.50 31.97

Apply method of last squares to determine the Conc. of MVK in a sample which yielded relative peak area 6.3, which is the mean of 4 measurements. Also calculate the standard deviation of the result.

  1. Give a critical account of acid-base titration in non-aqueous solvents.
  2. a) Determine the concentration of Fe2+, Fe3+, Ce4+ and Ce3+ in the mixture containing 20.00mL of 0.1000M Ce4+ and 40.00ml of 0.0500M Ce2+ in acidic medium.

(Eº Fe3+/Fe2+ = 0.8V, EºCe4+/ Ce3+ =1.4V)

  1. b) Discuss the factors which influence ∆Pm at the equivalence point.
  1. a) Explain the components of spectro flurometer with a neat diagram.
  1. b) What is hollow cathode? How does it work?
  1. a) Bring out the difference between TG and DTA.
  1. b) How will you prove the liberation of CO in a thermal analysis?
  1. A metal carbonate, MCO3.4H2O (at.wt of metal = 74) on thermal analysis becomes  dihydrate at  160˚C , monohydrate at 200˚C , anhydrous at 260˚C and MO at 550˚C Construct a TG, using graph sheet if 0.725 mg of the salt hydrate is heated from 40˚C to 750˚C.

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Loyola College M.Sc. Chemistry Nov 2006 Analytical Chemistry-III Question Paper PDF Download

                           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.  Ka 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 ip(a) , ip(c), Ep(a) and Ep(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 – 250o Co (at 400 – 500oC) and

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

Atmosphere.

 

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