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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