LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
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
Answer ALL questions (10 ´ 2 = 20 Marks)
- Calculate the ionic strength in 0.01M potassium ferricyanide solution.
- Explain the significance of symmetry factor in an electrode reaction.
- How does electrophoretic effect affects the ionic mobility in a solution of strong electrolyte?
- Explain IHP and OHP at the electrode – electrolyte interface.
- What is meant by Lippmann potential?
- Explain concentration polarization.
- Vant Hoff ‘ i ‘ factor for AB2 type electrolyte at a given concentration is 2.8. What is its percentage of ionization?
- Illustrate primary cell with an example.
- The solubility of mercurous chloride in water at 25o C is 1.0 x 10-5 mol dm-3 . What is its KSP value at the same temperature?
- What are surfactants? Give an example.
Answer any EIGHT questions (8 x 5 = 40 Marks)
11 State Debye – Huckel limiting law. How is verified?What is its limitation?
- Account for the abnormal mobilities of H3O+ and OH– ions in aqueous solution.
- How is the solubility product of a sparingly soluble salt like AgCl is determined from EMF measurements?
- Deduce Nernst equation from Butler – Volmer equation.
- Write briefly on Helmholtz – Perrin model for an electrical double layer.
- Distinguish between polarisable and non-polarisable electrodes with suitable examples.
- Explain the dependence of pH on corrosion using Pourbaix diagram.
- Write briefly on (i)Streaming potential (ii)Sedimentation potential
- Calculate the thickness of ionic atmosphere in 0.10M calcium chloride solution in water at 27o C . (Dielectric constant of water is 78.6)
- Write a note on H2 – O2 fuel cell.
- Explain Debye Falkenhagen effect.
Answer any FOUR questions ( 4 x 10 = 40 Marks)
- Derive Butler – Volmer equation for a single step single electron transfer reaction and explain the low and high field approximations.
- Discuss the Stern model for the electrode – electrolyte interface.
- Derive the Debye – Huckel – Onsager equation .
- a)Explain the amperometric method of estimation of silver nitrate.
b)What are electrocpillary curves?Explain its significance.
- 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 25o 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.