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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