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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI –600 034

M.Sc., DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – NOVEMBER 2003

CH – 3805/924 – ANALYTICAL CHEMISTRY

10-11-2003                                                                                                     Max:100 marks

1.00 – 4.00

 

PART – A

Answer ALL the questions.                                                                              (10×2=20 marks)

 

1. Explain constant error with an example.
2. C_e⁺⁴ + Ce⁺³   E^o = 1.44 V

S_n⁺⁴ + 2         Se⁺²   E^o = 0.15 V

Compute the equivalence point potential for the above system.

3. Explain replacement titration with an example.
4. Mention the factors which affect the p^M value at the equivalence point.
5. Calculate the equivalence point pH when 20.00 mL of 0.1000 M CH₃ COOH is titrated against 0.2000M NaOH (K_a for CH₃ COOH 1 x 10^-5)
6. How will you estimate phenol coulometrically?
7. Bring out the difference between Voltametric and potentiometric methods of analysis.
8. Explain the role of supporting electrolyte in polarography.
9. Explain why photoemission occurs at higher wave length than absorption.
10. What do you mean by carrier gas in GC? Give an example.

 

PART – B

Answer any EIGHT  questions.                                                                       (8×5=40 marks)

 

11. Calculate the concentration of Ce⁺⁴ and Fe⁺² in the mixture containing 20.00 mL of

0.100  N  Fe⁺² and 40.00 mL of 0.0500 N Ce⁺⁴ in acidic medium.  E= 1.44 V and E= 0.77 V.

12. What are metallochromic indicators? Give an example with the structure.  What are its characteristics?
13. How is an outlier rejected using Q-test.
14. Calculate the value of p^Zn in the mixture containing (I) 50.00 mL of 0.015 M Zn⁺² and 30.00 mL of 0.025 M EDTA (ii) 50.00 mL of 0.025 M Zn⁺² and 50.00mL of 0.050 M EDTA, both at pH 10.
15. Write a note on Von Weimarn’s theory.
16. Calculate the pH at which Mg(OH)₂ begins to precipitate from 0.1000 Mg(NO₃)₂.

K_sp  of Mg(OH)₂ = 1×10^-11.

17. What is DTGA? Compare it with DSC.
18. What do you men by steam distillation? What are the condition for a compound to be steam distilled?
19. A 0.5 millimolar solution of a divalent metal ion solution has diffusion current of 4 m The dropping rate of Hg was 24 drops½min.  The mass of 40 drops was found to be 15 mg.  Calculate the diffusion coefficient of the ion.
20. a) Explain the mechanism phosphorescence.
21. b) Explain the effect of the following on the intensity of fluorescence. (i) solvent (ii) pH

(iii) Dissolved oxygen.

21. Interpret the DTGA pattern of an inorganic compound with a suitable example.
22. a) Explain the principle of solvent extraction.
23. b) Obtain an expression for the amount of substance extracted at the end of nth extraction

using small volume of the extracting solvent each time.

 

PART – C

Answer any FOUR  questions.                                                                        (4×10=40 marks)

 

23. Give a critical account of acid base titrations in non-aqueous solvents.
24. a) A 1.0000g sample containing Na₂C₂O₄ requires 00 mL of 0.0200 M KMnO₄ the for

oxidation in acid medium.  Calculate the percentage of Na₂C₂O₄  in the sample and

express it scientifically.

1. b) A blood sample is sent to two different laboratories to be analyzed for cholesterol. The

results obtained for the concentration (mg/dL) were:

Laboratory I               Laboratory II

= 243                      = 258

s₁ = 13                         s₂   = 15

n₁ = 11                         n₂   = 11

1. Are the standard deviations significantly different at the 95% level?
2. Are the two means significantly different at the 95% level?

F value at 95% probability level for the above set corresponds to 2.98.  Students ‘t’

value at 95% probability level is 2.26.

25. a) What are the advantages and disadvantages of organic reagents in gravimetry?
26. b) A 0.3500 g sample containing KCl and KI gives a precipitate of AgCl and AgI that

weighs 0.2720 g.  A 0.5250 g sample of the same material is titrated with 0.1020 M

AgNO₃ requiring 25.80 mL.  Calculate the percentages of KCl and KI in the sample.

26. a) What is the difference between electro-gravimetric method and Coulometric method.
27. b) Explain the analytical method involved in the estimation Cu⁺² by
28. Electro gravimetric method
29. Polarographic method
30. a) Give the schematic representation of different types of variation of applied potential as

a function of time adopted in voltametry

1. b) Write a note on cyclic voltametry.
2. a) Draw the absorption, fluorescence and phosphorescence spectrum of a typical

compound.

1. b) Give the schematic diagram of a spectroflurometer and explain the components.

 

 

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             LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 26

FIRST SEMESTER – APRIL 2006

                                                    CH 1809 – ANALYTICAL CHEMISTRY

 

 

Date & Time : 25-04-2006/1.00-4.00 P.M.   Dept. No.                                                       Max. : 100 Marks

 

 

PART – A

Answer ALL the questions.                                                              (10 ´ 2 = 20)

1. Triethylamine is a good titrant for the estimation of Cu²⁺ but not ammonia. Why?
2. In what way is HPLC is different from GC?
3. Define confidence interval.
4. How is the indicator chosen for redox titration?
5. 00 ml of well water is found to contain10^-3 moles of ca²⁺. Express the concentration of Ca²⁺ in well water in ppm.
6. Mention two applications of differential thermal analysis (DTA).
7. What are the three electrodes used in cyclic voltametric experiment?
8. What is the significance of molar absorption coefficient?
9. What is hollow cathode lamp? Where is it used?
10. Suggest a method for the determination of (a) quinine (b) Na⁺ (c) Fe³⁺ in a tap water.

PART – B

Answer any EIGHT questions only.                                                         (8 ´ 5 = 40)

11. What is thermogram? Explain with an example.
12. Show that the fraction of completely ionized form of EDTA is a measure of pH.
13. A 50.00 ml of aliquot of a water sample containing Fe³⁺ required 13.75 ml of

1.2X10^-2 M EDTA when titrated at pH 2.0. Express scientifically the             concentration of Fe³⁺ in water sample in ppm.

14. 6000g sample consisting of only CaC₂O₄ and MgC₂O₄ is heated at 500 ֯C converting the salts to CaCO₃ and MgCO₃. The sample then weighs 0.4650g. If the sample had been heated at 900 ⁰C, where the products are CaO and MgO, what would be the mixture of oxides have weighed?
15. Find out the pH of the following solutions:
    20. Mixture of 20.00 ml of 0.0250 M acetic acid and 40.00 ml of 0.01250 M of sodium hydroxide. K_a of acetic acid is 10^-5.
    21. Mixture containing 20.00 ml of 0.0250 M sodium hydroxide and 20.00 ml of 0.0300 M HCOOH. K_a of HCOOH is 10^-2.
16. How will you proceed to collect authentic results for research?
17. How is sulphate determined by turbidimetric method?
18. How is Ni²⁺ estimated by spectrophotocoloriometric method?
19. How is florescence method more useful than the absorption method in some cases?
20. Write a note on anodic stripping voltammetry.
21. Write a note on deviations from Lambert-Beers law.
22. How is potassium estimated by flame photometric method?

 

PART – C

Answer any FOUR questions only.                                                     (4 ´ 10  = 40)

23. Discuss the principle and instrumentation of Gas Chromatography.
24. The sulphate concentration I natural water can be determined by measuring the turbidity that results when excess BaCl2 is added to a measured quantity of the sample. A turbidimeter was calibrated with a series of standard sodium sulphate solutions. The following data were obtained in the calibration.

mg/L                           Reading

0.0                               0.06

0.5                               1.48

• 28
• 98

20.0                             4.61

Assuming a linear relationship, derive the equation for the best straight line though these points. Assuming the turbidimeter reading 3.67 for the unknown sample which is the mean of 3 readings, calculate the standard deviation of the result and the concentration of sulphate in the sample.

25. Discuss the applications of Thermogravimetry. (6)
26. Explain how the concentration of analyte and products are estimated at the equivalence point in redox titration.
27. How is thermogravimetry recorded? Mention the factors that affect the thermo gravimetric curves.
28. Describe the estimation of copper by electrogravimetric method.
29. Describe the principle and instrumentation involved in atomic absorption method. How is Ca²⁺ in ppm levels estimated by this method?

 

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                        LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

AD 17

FIRST SEMESTER – NOV 2006

CH 1809 – ANALYTICAL CHEMISTRY

 

 

Date & Time : 02-11-2006/1.00-4.00   Dept. No.                                                       Max. : 100 Marks

 

 

PART – A

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

 

1. A Chemical balance is used to weigh 2.0000g of FAS.  Find out the maximum relative uncertainty associated with the weight in ppt.
2. Determine the pH of the mixture containing 20.00 mL of 0.0750 m CH₃COOH and
   30.00 mL of 0.0500 M NaOH.  K_a of CH₃COOH is 1 x 10^-5.
3. How does GSC differ from GLC?
4. Mention the factors which affect pm at the equivalence point.
5. How does AAS differ from Flame photometry?
6. Explain why MgCo₃ is thermally less stable compared to Na₂CO₃.
7. What is the difference between DTA and DSC.
8. What will be the mass of ion deposited by a current of 9.65 A in 2 minutes passed in to a solution of ferric chloride(Fe : At . wt = 55.85)?
9. How many faraday current is required to reduce one mole of MnO₄ to mn²⁺.
10. State Beer Lambert’s Law.

 

PART – B

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

 

1. Apply ‘t’ test and ‘F’ test to check whether two sets of data differ significantly or not.
2. Discuss the principle of GLC.
3. Draw the titration curves for the following and interpret the result.

• 00 mL of 10^-1M CH₃ COOH vs 10^-1M NaOH
• 00 mL of 10^-2 M CH₃ COOH vs 10^-2 M NaOH

1. Show that the fraction of completely ionized form of EDTA depends on pH.
2. A solution containing 8.75 ppm KmnO₄ has a transmittance of 75% in a  1 cm cell at
   520 nm.  Calculate the molar absorptivity of KmnO₄.
3. The organic matter in a 0.3775 g sample of a mercuric ointment is decomposed with HNO₃ .  After dilution the Hg⁺² is titrated with 21.30 mL of a 0.1140 M solution of NH₄SCN.  Calculate the % of Hg (f.w = 200.59) in the ointment and express it scientifically                 Hg⁺² + 2SCN⇌  Hg(SCN)₂ .
4. Cupric nitrate decomposes as follows.

Cu (NO₃)₂ .2½ H₂O  Cu (NO₃)₂ + 2½ H₂O (100-150^oC)

Cu(NO₃)₂   CuO + NO₂ + 1½ O₂ (200 – 280^oC)

Calculate the residual mass if 100 mg of hydrated cupric nitrate in heated upto 250^oC.

1. Calcium oxalate monohydrate undergoes three types of weight loss, whereas magnesium oxalate shows only two types of weight loss.  Explain.
2. How will you estimate copper electro gravimetrically?
3. Calculate the emf w.r.f  SCE when 1 ml of 0.25 m K₂Cr₂O₇ is added to 20 ml of 0.05 m Fe²⁺ in 0.1 m HCl.
4. Explain the coulometric titration of I^–   Vs   S₂O₃ ^2–
5. Explain the quantitative application of polorography.

 

PART – C

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

 

1. Potassium can be determined by flame emission spectrometry using a lithium internal standard.  The following data were obtained for standard solutions of KCl and an unknown containing a constant known amount of LiCl as internal standard.  All the intensities were corrected for background by subtracting the intensity of a blank.

Conc K, ppm	Intensity of Emission
1.0	10.0
2.0	15.3
5.0	34.7
7.5	65.2
10.0	95.8
Unknown	47.3

 

Apply the method of least squares to obtain the equation for the best straight line through these points.  Determine the standard deviation of the slope and the result, if the unknown intensity corresponds to the mean of 4 measurements.  Also find out the concentration of K in the unknown.

1. Draw the flow sheet diagram of HPLC and explain the function of the components.
2. a) A 0.4085 g sample containing pb, mg and Zn was dissolved and treated with cyanide     to complex and mask the zinc;

Zn⁺² + 4 CN^–   [Zn(CN)₄] ^2–.

Titration of the lead and magnesium required 42.20 ML of 0.02065 M EDTA.  The lead was next masked with BAL (2,3 dimercaptophepanol), and the released EDTA was titrated with 19.35 mL of 0.007650 m Mg⁺² solution.  Finally HCHO was introduced to demask the Zinc;
[Zn(CN)₄] ^2– + 4HCHO + 4H₂O Zn⁺² + 2OH^– + 4 CNCH₂OH.
The zinc was then titrated with 28.60 mL of 0.02065 EDTA.  Calculate the percentages of the three metals in the sample.                                                         (7)

1. b) Explain the principle of Flame Photometry. (3)

1. a) How will you prove the liberation of Carbon monoxide by thermal analysis.

2. b) 2.92 mg of a sample of mgSo₄.7H₂O losses 0.62 mg at 105^o C due to the following

reaction
MgSo₄.7 H₂O   MgSO₄.H₂O + 6H₂O.

calculate the % purity of the sample.

1. Explain the potentimetric titration of acidified Fe²⁺ against standard MnO₄^–

[SRP: Fe³⁺, Fe²⁺ = 0.77       MnO₄^–, Mn²⁺, H⁺ = 1.51 V]

Write the electrode  reactions before and after the equivalence point and draw the titration   curve.

1. a) Explain the instrumentation of a classical fluorimeter.

1. b) Explain the applications of Cyclic voltametry.

 

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

LM 29

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FIRST SEMESTER – APRIL 2007

CH 1809 – ANALYTICAL CHEMISTRY

 

 

Date & Time: 02/05/2007 / 1:00 – 4:00      Dept. No.                                       Max. : 100 Marks

 

 

PART – A

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

 

1. What is Correlation Coefficient? What is its significance?
2. 00 ML of well water is found to contain 0.0400g calcium ion. Express the concentration of Ca⁺² in Well water in ppm.
3. Mention the factors which affect the p^m value in complexometry.
4. Draw the titration curves for the following.
   • 00ML of 10^-2 M H₂ SO₄ vs 10^-2 M NaOH.
   • 00ML of 10^-2 M vs  10^-2 M NaOH.

 

5. List the factors which influence the thermogram.
6. State the principle involved in the analysis of Fe³⁺ by Spectrophotocolorimetric Method.
7. Match the following:

(i)  Electrogravimetry   (ii)  Flame Photometry  (iii) Polarography  (iv)  Flourescence  Method.

 

(A) K⁺  (B) Pb²⁺,  Bi³⁺ in a mixture (C) Cu²⁺  (D)  Benzphrene in cigarette Smoke.

 

8. B_e, Al, and La cannot be accurately determined by atomic absorption method.
9. 28 of p-vitrophenol in IN-NaOH showed an absorbance of 0.500 at 400mm. The thickness of the all used is 0.1cm.  Calculate the molar absorption coefficient .
10. Mention the principle used in the anodic stripping voltammetry.

 

PART – B

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

 

11. How are Authentic Results produced in research?
12. Show that the equivalence point potential for   is dependent on P^H.
13. Compare at the equivalence point for the following titration’s:
    • 00ML of 0.0250M
    • 00ML of 0.0250M CH₃ COOH vs 0.0250M O(Ka for CH₃ COOH is 10^-5)

 

14. Ka₁, Ka₂, Ka₃ and Ka₄ for EDTA are 10^-2, 10^-3, 10^-8 and 10^-12 respectively. Calculate the        conditional stability constant for the following in 10^-2 M  .

 

.

15. Discuss the thermogram of CuSO₄.5H₂O.

 

16. Explain the principle of gas chromatography.

 

17. How is Lambert-Beer’s Law verified? Mention the deviations.

 

18. How are the sensitivity and selectivity enhanced in the spectrophotocolorimetric method of         analysis?
19. Mention any tour applications of Spectroflourimetric Method of analysis.

 

20. How is Castant potential Calomety carried out?

 

21. Discuss the estimation of sulphate by turbidimetric method.

 

22. How is cyclic voltammogram recorded? Discuss the parameters that influence the peak potentials and peak current.

PART – C

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

 

23. A standard solution was put through appropriate dilutions to give the concentrations of Fe(II) shown below.

 

The Fe(II)/i,  10 Phenanthroline complex was then developed in 25.00ML aliquots of these solutions, following which each was diluted to 50.00ML.  The following absorbance’s (1.00cm cell)  were recorded at 510 mm.

Conc.  of Fe(II); ppm	A510
4.00	0.160
10.00	0.390
16.00	0.630
24.00	0.950
32.00	1.260
40.00	1.580

Assuming a linear relationship between the variables, apply the method of least squares to arrive at the equation for the best fit.  Calculate the concentration of Fe(II) in a sample that gave an absorbance of 1.510 which is the mean of three measurements.  Also calculate the standard deviation of the slope and the result.

 

24. Calamine which is used for relief of skin irritations is a mixture of ZnO and Fe₂O₃. A 1.022g sample of dried calamine was dissolved in acid and diluted to 250.00ML.  KF was added to a 10.00ML aliquot of the diluted solution to mask the iron;  after suitable adjustment of the P^H the Zn⁺² consumed 38.78 ML of 0.01294M EDTA.  A second 50.00ML aliquot was suitably buffered and titrated with 2.40ML of 0.002727 M ZnY^-2  solution;

Fe⁺³ + ZnY^-2  →  FeY^– + Zn⁺².

 

Calculate the percentages of ZnO and Fe₂O₃ in the sample.  Compare the stability constants of  ZnY^-2  and  FeY^–.

 

25. Plot the titration curve for the titration of 40.00ML of 0.0125M Mg⁺² vs 0.0500M EDTA. Keff for MgY^-2 at P^H 10 is 10¹⁸.

 

26. Describe the estimation of Copper by electrogravimentric method.

 

27. Discuss the principle and instrumentation involved in atomic absorption method. How is ICP method is more superior to AAS method?

 

28. Describe the polarograpic set-up. How are Zn²⁺ and Cd²⁺ in a mixture can be analysed by its method.

 

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

GH 29

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FIRST SEMESTER – APRIL 2008

    CH 1809 – ANALYTICAL CHEMISTRY

 

 

 

Date : 05/05/2008            Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

PART A

Answer ALL questions                                                                  (10 ´ 2 = 20 Marks)

 

1. A method of analysis yields weights for gold that are low by 0.4 mg.

Calculate the percent relative error caused by this uncertainty if the weight

of gold in the sample is 0.4 g.

2. What is meant by retention time?
3. Mention one advantage and one disadvantage of flame ionization detector

in gas chromatographic separation.

4       .Illustrate displacement titration with an example.

5       In what respect Fajans method superior to the Volhard method for the

titration of chloride ion?

6. Explain any two factors that affect the thermogram.
7. Calculate the equivalent point potential in the titration of Fe²⁺ vs Ce^+4.

( SRP    Fe³⁺ /Fe⁺² = 0.68 V ;  Ce⁺⁴ / Ce⁺³ = 1.44 V)

8       .Illustrate metallochrome indicator with an example.

9. What are the limitations of Beer – Lambert’s law?
10. Write the Ilkovic equation and explain the terms.

 

PART B

Answer any EIGHT questions                                                      (8 ´ 5 = 40 Marks)

 

11. A 7.27 x 10^-5 M solution of KMnO₄  has a transmittance of  44.1% when

measured in a 2.1 cm cell at a wave length of 525 nm. Calculate the

molar absorptivity of KMnO₄ .

12. Distinguish clearly between precision and accuracy.
13. Explain the various factors which affect the equivalence point in

complexometric titrations.

14. Draw the TG thermogram of calcium oxalate monohydrate obtained

when it is heated to 700^o C and explain.

15. Describe the flame ionization detector used in GC.
16. Explain the principle and application of capillary electrophoresis.
17. How is Cu²⁺ estimated by electrogravimetric method?
18. What are determinate and indeterminate errors and suggest the

methods for minimization of these errors.

19. Explain the components of a spectrofluorometer with a neat diagram.
20. What are the advantages of DME?
21. Explain the function of adsorption indicators in precipitation titrations.
22. What is meant by half-wave potential?What is its significance?

 

 

 

PART C

Answer any FOUR questions                                                             ( 4 ´ 10 = 40 Marks)

 

23. Describe with a block diagram the various parts of the instrument used in

AAS and explain the their functions.

24. a)Write briefly on masking and demasking agents.

b)Describe Fajans method for the estimation of chloride.

25. a)Explain the various factors which affect fluorescence emission .

b)Show that the equivalent point potential in the titration of ferrous ion

against permanganate is pH dependent.

26. Discuss the principle of Cyclic voltammetry and its use in the determination

of electrochemical reversibility and stability of a redox system.

27. Describe the HPLC instrument with a neat diagram and the different

types of columns employed.

28. Carry out a least -squares analysis of the experimental data obtained in

the chromatographic determination of iso-octane in a hydrocarbon mixture

and derive the equation for the best line through these ponts:

 

Mole pecent isooctane (x_i )                                         Peak area (y_i )

0.352                                                               1.09

0.803                                                               1.78

1.08                                                                 2.60

1.38                                                                 3.03

1.75                                                                 4.01

 

 

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

DB 24

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FIRST SEMESTER – November 2008

    CH 1809 – ANALYTICAL CHEMISTRY

 

 

 

Date : 11-11-08                 Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

PART A

Answer all the questions.                                                                                  10 x 2 = 20

1. Lead was determined in a sample of dust and the following results were obtained

4.3, 4.1, 4.0 and 3.2 µg /g. Should the last value 3.2 µg /g be rejected? The critical value of Q for four measurements is 0.831.

2. What are gross errors?
3. Define intersystem crossing.
4. Mention any four compounds used to derivatise the samples for GC.
5. A random sample of 9 observations shows a mean of 4.13 with a standard deviation of 0.189. Test whether the sample values deviate from the mean of 4.0. (t_95% = 2.306)
6. How much of NaF must be added in 1000 liters of water so that the concentration of F^– is equal to 1 ppm?
7. What is a masking agent? Give an example.
8. Differentiate coulometry from voltammetry.
9. Write Ilknoic equation and mention the terms involved.
10. Calculate the pH at the equivalence point when 20 ml of 0.1M NH₄OH is treated with 0.2M HCl _(aq) . K_b of NH₄OH is 1.8 x 10 ^-5.

PART B

Answer any eight questions.                                                                                8 x 5 = 40

11. What are determinate errors? Explain any four types of determinate errors.
12. On heating NaHCO₃ (Mol. weight is 84) it decomposes between 100 – 225°C with the loss of H₂O and CO₂. The total weight loss due to H₂O and CO₂ is 35.8 percent by weight, whereas the weight loss due to CO₂ alone is 25.4%. Calculate the millimoles of NaHCO₃ decomposed and deduce the stoichiometry of the reaction.
13. What are the different types of columns used in GC? Explain.
14. The normality of a solution is determined by four separate titrations, the results being 0.2041, 0.2049, 0.2039 and 0.2043. Calculate the mean, median, average deviation, standard deviation and coefficient of variation.
15. Discuss the types of burners used in AAS and mention any one advantage for each.
16. How is codeine and morphine in a mixture determined by fluorimetry?
17. Explain the salient features of non-aqueous acid-base titrations with a specific example.
18. Calculate the molar solubility of BaSO₄ in 0.01M NaNO₃ solution (the thermodynamic solubility product of BaSO₄ at 25°C is 10 ^-10.
19. 50 ml of 0.0.1M Ca ²⁺ is titrated with 0.01M EDTA at pH= 10. K_abs for CaY^2- is 5 x 10 ¹⁰ and a₄ at pH 10 is 0.35. Calculate p_ca after adding 60 ml of the titrant.
20. Derive an expression for equivalence point potential for the redox reaction between Cr₂O₇ ^2- and Fe²⁺ in acid medium to form Cr³⁺ and Fe³⁺.
21. Explain the working of a biochemical ion selective electrode with an example.
22. Discuss the theory of adsorption indicators in precipitation titrations.

 

PART C

Answer any four questions.                                                                              4 x 10 = 40

23. What are spectrophotometric titrations? How are they carried out? Explain the different types of spectrophotometric titrations with examples.
24. a) Explain the factors affecting the fluorescence emission.
25. b) Write short notes on the chemical interferences in flame emission spectroscopy.                                                                                                    (5+5)
26. a) Draw and explain the working principle of flame ionization detector.
27. b) Explain briefly the instrumentation in turbidimetry.                                     (5+5)
28. Calculate the relative error when 50 ml of 0.1M Cl^– is titrated with 0.1M AgNO₃. The initial concentration of K₂CrO₄ (indicator) is 2 x 10 ^-3M. Assume that the titration is stopped at the very onset of Ag₂CrO₄ precipitate formation. K_sp of AgCl and Ag₂CrO₄ are 1.8 x 10 ^-10 and 1.2 x 10 ^-12 respectively.
29. Explain any two of the following:
30. a) Principle and applications of stripping voltammetry
31. b) colulometric titration
32. c) Feasibility of acid-base titrations
33. d) Metallochrome indicators. (5+5)
34. 0.7362g of sample containing only Ca(NO₃)₂.4H₂O, NaCl and KCl is dissolved in water and diluted to 100 ml. (solution X). A 25 ml portion of X is titrated with 25 ml of 0.01M EDTA. Another 25 ml portion of X is treated with 25 ml of 0.1M AgNO₃ and excess of Ag⁺ is back titrated with 4 ml of 0.1250M KSCN solution. Calculate the percentage of each in the sample.

 

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       LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

WD 28

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

1. Round each of the following numbers to four and three significant figures
2. a) 28755 b) 0.002045
3. 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)

3. How are the samples derivatised in gas chromatography?
4. What are the factors affecting the flame temperature of the burners in flame spectrometry?
5. What is the principle of atomic absorption spectroscopy?
6. Differentiate the formality of a solution from molarity with an example.
7. Acetic acid has autoprotolysis constant of 3.55 x 10^-15. Calculate the pH of pure acetic acid.
8. 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.
9. Mention the significance of selectivity coefficient in ion selective electrode.
10. What are the advantages of dropping mercury electrode?

PART B

Answer any eight questions.                                                                                8 x 5 = 40

11. Write short notes on chemical interferences in flame emission spectroscopy?
12. What are the different types of pumps used in HPCL? Explain.
13. How is the purity of pharmaceuticals determined by DSC?
14. Explain the advantages and disadvantages of using premix and total consumption burners used in AAS.
15. How is sulphate determined by turbidimetry?
16. Discuss the fluorimetric determination of quinine.
17. 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.

 

18. Derive an expression for equivalence point potential for the redox reaction between MnO^4- and Fe²⁺ in acid medium.
19. Explain the effect of i) complexation, ii) adding an indifferent electrolyte as the solubility of a sparingly soluble salt with suitable example for each.
20. What is the origin of polarographic maxima? Explain.
21. 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.
22. How is Sb³⁺ estimated using coulometry?

 

PART C

Answer any four questions.                                                                              4 x 10 = 40

23. Explain the principle and instrumentation of capillary electrophoresis.
24. a) Draw and explain the thermal decomposition of CuSO₄.5H₂O by TGA and

DTA studies.

1. b) Discuss the various types of detectors used in GC. (5+5)
2. What are spectrophotometric titrations? Explain the types with the advantages.
3. Explain any two of the following:
4. a) principle of cyclic voltammetry
5. b) solid state ion selective electrodes
6. c) non-aqueous titrations
7. d) Ilkovic equation
8. 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)
9. 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. K_sp for AgBr is 5 x 10^-13.
10. b) What is the principle of Volhard’ method? (6+4)

 

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