LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034 B.Sc. DEGREE EXAMINATION – CHEMISTRY

AD 10

FIFTH SEMESTER – NOV 2006

CH 5501 – ANALYTICAL CHEMISTRY

(Also equivalent to CHE 509)

 

 

Date & Time : 27-10-2006/9.00-12.00   Dept. No.                                                       Max. : 100 Marks

 

 

 

Part A

Answer all the questions.                                                                                      10×2=20

1. Define chromophores with an example.
2. Calculate the number of photons emitted in one second from a 100W red lamp, assuming that the photons emitted by the lamp have an average wavelength of 694 nm (1W = 1 Js^-1)
3. What is Von Weirman ratio?
4. How many normal modes of vibrations possible for CO
5. Calculate the molarity of a solution, which contains 6.00g of NaCl in 200 ml of the solution.
6. What is meant by precision?
7. Calculate the relative average deviation of following set of values in titration experiment 9.8, 10.6, 10.8 and 10.4 ml.
8. Define the term absolute error.
9. What are the factors affecting the solubility product?
10. What are the various cleaning agents commonly used for cleaning glasswares?

 

Part B

Answer any eight questions.                                                                                  8×5=40

 

11. What are the requirements of a primary standard?
12. Explain quinonoid theory for phenolphthalein and methyl orange.
13. A compound of molecular weight 100 has a molar absorptivity of 1.00×10⁵ l mol^-1 cm^-1. How many grams of this compound should be present in exactly in 1 litre of the solution so that after a two hundred-fold solution, the resulting solution will have an absorbance of 0.5 in a 1 cm cell?
14. A sample of pure NaCl (MW=58.44) weighing 0.2286g is dissolved in water and exactly 50ml of AgNO₃ is added to precipitate AgCl. The excess Ag⁺ is backtitrated with 12.56ml of 0.0986N solution of KSCN. Calculate the normality of AgNO₃
15. What are the procedures employed to minimize the coprecipitation.

 

 

 

16. What is S/N ratio? How is it improved?
17. Explain the terms threshold vapor concentration and universal antidote.
18. In two separate determinations, the concentration of iron in a given sample was found to be a) 20.17 ppm b) 19.80 ppm. Taking the accepted value as 20.00 ppm, calculate the absolute error, relative error as percent and as parts per thousand in the two determinations.
19. What is R_f value? What are the factors affecting R_f value?
20. In the precipitation reaction when 0.0500M AgNO₃ is added to 25.00 ml of a solution that is 0.0150M NaCl, 0.0100M NaBr, calculate the concentration of silver ion.
21. Explain the development of chromatogram in TLC. Give its applications.
22. Write a note on normal error curve and explain its importance.

 

Part C

Answer any four questions.                                                                                 4x 10=40

 

 

23. How is UV-Visible spectrum recorded by double beam spectrophotometer?
24. What are the factors affecting e_max and l Explain with examples.
25. a) Derive Henderson equation for acidic buffer.
26. b) How is Volhard method used for the determination of chloride? (5+5)
27. a) Explain the principle of steam distillation.
28. b) Describe with diagram how a substance can be purified by this method. (5+5)
29. Explain the theory behind the separation of mixture by column chromatography. Mention its applications.
30. In a set of measurements the following concentrations of Fe (ppt) was reported:

20.21, 20.41, 20.31, 20.11, 19.91, 20.01 and 19.81.Calculate a) average deviation

1. b) standard deviation   c) relative standard deviation   d) coefficient of variation   e) range.

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 14

FIFTH SEMESTER – APRIL 2007

CH 5501 – ANALYTICAL CHEMISTRY

 

 

 

Date & Time: 28/04/2007 / 1:00 – 4:00 Dept. No.                                                Max. : 100 Marks

 

 

 

PART A

 

Answer the following                                                                             10×2 = 20

 

1. What are antidotes? Cite two examples.
2. What is sublimation? Mention two compounds which can be purified by this method.
3. How is adsorption different from absorption? Name one analytical technique, which uses adsorption phenomenon?
4. What are R_f values? Mention their significance.
5. What are primary standards and secondary standards?
6. What is solubility product? What is its application?
7. Distinguish end point from equivalence point.
8. What is the unit for measuring strength of an acid? Give its mathematical expression.
9. Explain coprecipitation and post precipitation.
10. Give an account of Beer-Lambert’s law. What is its use?

 

 

PART B

Answer any eight of the following:                                                       8×5 = 40

 

11. How are burettes and standard flasks calibrated?
12. Explain various types of errors.
13. Give the principle involved in solvent extraction technique, with special reference to distribution coefficient.
14. How is an aromatic carboxylic acid recrystallised?
15. Describe the detection of compounds by thin layer chromatographic technique.
16. Molecular weight of a dibasic acid is 50. What is the amount of this acid required to prepare 250mL of its 0.2N solution?
17. Derive Henderson’s equation.
18. Describe precipitation titration with an example.
19. The solubility product of a sparingly soluble MX type salt is 10 ^-14 at 25⁰ Calculate its solubility in molarity if its molecular weight is 100.
20. What are the precautions to be taken to avoid error while precipitating a compound in gravimetric analysis?
21. What are Selection Rules? Give selection rules for electronic (UV- vis) spectroscopy.
22. Taking a planar triangular molecule as example, explain various types of vibrations. (Show sketch)

 

 

Cond….2

 

 

 

 

PART C

 

Answer any four of the following:                                                        4×10 = 40

 

23. Write an essay on errors in chemical analysis, with special reference to types and minimizing the same.
24. Explain fractional distillation with an example.
25. In principle, how is ion exchange chromatography different from other chromatographic techniques? How is this technique useful in softening of water?
26. Discuss complexometric titrations.
27. How is indicator decided for an acid – base titration? Explain using phenolphthalein and methylorange as indicator.
28. Write short notes on (i) chromophores

(ii) auxochrome

(iii) signal to noise ratio

(iv) line-width

 

 

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