LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

WD 01

FIFTH SEMESTER – April 2009

CH 5500 – PHYSICAL CHEMISTRY – II

 

 

 

Date & Time: 16/04/2009 / 9:00 – 12:00    Dept. No.                                              Max. : 100 Marks

 

 

PART – A

Answer ALL questions                                                                                               (10 x 2 = 20)

1. Write calomel electrode reaction as reduction.
2. NaCl cannot be used in salt bridge. Why?
3. E^ocell is 1.10V for Zn + Cu²⁺ → Zn²⁺ + Cu. Calculate ∆G^o cell at 298K.
4. What are concentration cells? Give one example.
5. Define transport number of an ion.
6. 30% of a first order reaction is complete in 100 min. Calculate the rate constant of the reaction.
7. What is the effect of ionic strength on the rate constant of a reaction of the type A^– + B^– →

products in solution phase.

 

8. Mention the steps involved in a thermal chain reaction.

 

9. “Adsorption is spontaneous and mostly exothermic”.
10. Define quantum yield of a photochemical reaction.

PART – B

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

11. Derive Nernst equation for a cell reaction and hence deduce an expression for equilibrium constant for the cell reaction.
12. Calculate E^o cell, Ecell, ∆G^o cell and ∆G cell for Zn|Zn²⁺ (0.01M) ||Ag⁺ (0.01M) |Ag at 298k. E^ored Zn⁺²|Zn – 076V and Ag⁺|Ag 0.8V.  Assume n = 2.  Write the electrode reactions.
13. Write down the electrode reactions in a) lead storage cell   b) H₂ – O₂ fuel cell.  Mention one salient feature for each.                                                                                 (3+2)
14. What is Weston – Cadmium cell? Explain its construction and indicate the electrode reactions.                                                                                                                      (2+2+1)
15. How is transport number of an ion determined experimentally?
16. Explain the variation of equivalent conductance with concentration for
17. a) strong electrolyte b) weak electrolyte in water with suitable graph. (2+2+1)
18. Differentiate order form molecularity.
19. Explain the principle of conductometric titrations with one example.
20. The rate of a first order reaction is doubled on increasing the temperature from 27^oC to 37^oC (R=8.314 JK^-1 mol^-1.)   Calculate the activation energy of the reaction.
21. State the postulates of Langumir adsorption isotherm and hence derive the equation. (2+3)
22. Write briefly on i) photosensitization ii) chemiluminescence.
23. Derive an expression for rate constant of a second order reaction of the type 2A →products.

PART – C

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

23) a) Explain how ∆G^o, ∆H^o, ∆S^o of a cell reaction be determined using EMF measurements.    (6)

1. b) Explain the significance of electromotive series.                 (4)
2. Give an account of any two of the following a) types of electrodes with the relevant Nernst

equations.  b) determination of Ksp of a salt using EMF.  c) Principle for potentiometric acid –

base titrations.  d) standard hydrogen electrode.

25. a) Derive an expression for Ecell for a chemical cell with transference (6)
26. b) How is Ka of weak acid determined using conductance measurements?                         (4)
27. a) Explain any two methods of determining order of a reaction (6)
28. b) Discuss the mechanism of S_N2 reaction with an example. (4)
29. Explain the kinetics of single substrate enzymatic reaction. How are the kinetic parameterms

evaluated?                                                                                                                               (6+4)

28. Write notes on any two of the following (5+5)
29. a) Debye-Huckel theory of strong electrolytes
30. b) Principle of polarography
31. c) Quinhydrone electrode & its use.
32. d) Parallel reactions.

 

 

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