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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