LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

GH 59

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FOURTH SEMESTER – APRIL 2008

    CH 4805 / 1020 – ELECTROCHEMISTRY

 

 

 

Date : 03/05/2008            Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

PART A

Answer ALL questions                                                                      (10 ´ 2 = 20 Marks)

 

1. Calculate the ionic strength in 0.01M potassium ferricyanide solution.
2. Explain the significance of symmetry factor in an electrode reaction.
3. How does electrophoretic effect affects the ionic mobility in a solution of strong electrolyte?
4. Explain IHP and OHP at the electrode – electrolyte interface.
5. What is meant by Lippmann potential?
6. Explain concentration polarization.
7. Vant Hoff ‘ i ‘ factor for AB₂ type electrolyte at a given concentration is 2.8. What is its percentage of ionization?
8. Illustrate primary cell with an example.
9. The solubility of mercurous chloride in water at 25^o C is 1.0 x 10^-5 mol dm^-3 . What is its K_SP value at the same temperature?
10. What are surfactants? Give an example.

PART B

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

 

11  State Debye – Huckel limiting law. How is verified?What is its limitation?

12. Account for the abnormal mobilities of H₃O⁺ and OH^– ions in aqueous solution.
13. How is the solubility product of a sparingly soluble salt like AgCl is determined from EMF measurements?
14. Deduce Nernst equation from Butler – Volmer equation.
15. Write briefly on Helmholtz – Perrin model for an electrical double layer.
16. Distinguish between polarisable and non-polarisable electrodes with suitable examples.
17. Explain the dependence of pH on corrosion using Pourbaix diagram.
18. Write briefly on (i)Streaming potential (ii)Sedimentation potential
19. Calculate the thickness of ionic atmosphere in 0.10M calcium chloride solution in water at 27^o C . (Dielectric constant of water is 78.6)
20. Write a note on H₂ – O₂ fuel cell.
21. Explain Debye Falkenhagen effect.

PART C

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

 

22. Derive Butler – Volmer equation for a single step single electron transfer reaction and explain the low and high field approximations.
23. Discuss the Stern model for the electrode – electrolyte interface.
24. Derive the Debye – Huckel – Onsager equation .
25. a)Explain the amperometric method of estimation of silver nitrate.

b)What are electrocpillary curves?Explain its significance.

26. a)How does hydrogen over voltage arise?

b)Describe any two methods employed for the prevention of corrosion.

27.a)The equilibrium exchange current density for the reaction

H⁺  +  e ^–  →     H₂

on nickel  at 25^o C is 1.00 x 10^-5  A cm^-2 . What current density would be

necessary to attain a cverpotential of 0.1V ? (α = 0.5).

b)For Weston standard cell at 298K emf is 1.01032 V and temperature

co-efficient of  emf of the cell is -5.00 x 10^-5  VK^-1  . Calculate ∆ G , ∆H

and  ∆ S of the cell reaction.

 

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