LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

           B.Sc. DEGREE EXAMINATION – CHEMISTRY

GH 18

FIFTH SEMESTER – APRIL 2008

CH 5500 – PHYSICAL CHEMISTRY – II

 

 

 

Date : 28-04-08                  Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

 

part – a

            Answer all questions.                                                            (10 ´ 2 = 20 marks)

 

1. Why can’t you use NaCl in salt bridge preparation of a galvanic cell?
2. For the cell reaction at 25° C, Zn½Zn²⁺⁺½½Cu²⁺½Cu     E°_cell = 1.10 V

Calculate equilibrium constant for the  reaction.

3. Define molar conductance of a solution.
4. What is transport number?
5. Calculate the ionic strength of 0.01 M KNO₃
6. 30% of a zero order is complete in 100 min. How long will it take for 60% completion of the reaction?
7. Mention the steps involved in a chain reaction
8. Differentiate adsorption from absorbtion
9. Mention the significance of the equation q =
10. State Grotthus – Drapper’s law.

 

PART – B

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

 

11. Derive Nernst equation for a cell reaction.
12. Calculate E°_cell, E_cell, DG°_cell and DG_cell for

Cu½Cu²⁺(0.01 M)½½Ag⁺(0.001 M)½Ag at 298 K.  E°_red  Cu²⁺½Cu and Ag⁺½Ag are 0.34 V

and 0.8 V respectively.

13. Explain the construction and working of calomel electrode.
14. State and explain Kohlrausch’s law of independent migration of ions.
15. Write the electrode reactions and the net reaction of lead storage cell when it serves as source of current.
16. Explain the principle of conductometric acid-base titrations with an example.
17. Explain the mechanism of bimolecular surface reaction.
18. How does Λ vary with concentration for

(i) strong electrolyte        (ii) weak electrolyte

19. The rate of a reaction is doubled on increasing the temperature from 25° C to 35°  Calculate the activation energy of the reaction.  (R = 8.314 JK^-1mol^-1).
20. Derive an expression connecting rate constant and concentration of a II order5 reaction of the type 2A ®
21. Differentiate (i) order from molecularity (ii) EMF and potential difference.           (3 + 2)
22. Define quantum yield of a photochemical reaction. How is it determined?                        (2 + 3)

 

 

 

PART-C

   Answer any FOUR questions.                                                            (4 ´ 10 = 40 marks)

 

23.(a) Explain any two methods of determining order of a reaction.       (6)

(b) t_1/2 of C-14 is 5770 years.  Calculate the rate constant.  Starting from 100 mg
of  C-14 how much of it will remain at the end of 17,310 years.              (4)

24. Discuss the kinetics of unimolecular reaction with relevant derivation of the rate law.
25. Explain any two of the following: (5 + 5)

(a) Quinhydrone electrode and its use.

(b) Evaluation of thermodynamic quantities from EMF data.

(c) H₂-O₂ fuel cell.

(d) Determination of K_sp using conductometry.

26. (a) Explain how transport number of an ion be determined using moving
    boundary method?

(b) Explain the functioning of glass electrode.

27. Explain any two of the following:

(a) Electrochemical series

(b) Cells with transference

(c) Determination of EMF

(d) Weston Cadmium cell

28.(a) Explain the postulates of Langumir adsorption isotherm and hence derive the
equation.

(b) Write briefly on photosensitisation.

 

 

 

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