LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

LM 17

B.Sc. DEGREE EXAMINATION – CHEMISTRY

SIXTH SEMESTER – APRIL 2007

CH 6600 – MOLECULAR DYNAMICS

 

 

 

Date & Time : 16.04.2007/9.00-12.00      Dept. No.                                                      Max. : 100 Marks

 

 

 

 

Part A

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

1. Define (i) particle (ii) wave
2. Bring out the difference between photoelectric effect and Zeemann effect.
3. Determine the Eigen value for “Ae^-ax for the operator (d/dx²)”^.
4. What is the condition for φ₁ and φ₂ to be orthogonal functions in the interval [a,b]
5. Explain the difference between thermodynamic probability and mathematical probability?
6. Explain phosphorescence in terms of spin multiplicity
7. Define quantum yield of a photochemical reaction.
8. Define steady state approximation. What is its advantage?
9. What is residual entropy? Give an example.
10. Calculate the number of ways of distributing 4 fermions among 8 energy levels.

 

 

Part B

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

 

 

11. Explain the energy distribution in black body
12. An electromagnetic radiation of wave length 200Å is incident on a metal surface of threshold frequency 6.53×10¹⁴ Hz .Calculate the velocity of the electrons emitted.
13. Calculate the wave length of the lowest energy of the Balmer
14. Calculate the ground state energy of a π-electron in 1, 3-butadiene. (The C=C & C-C bond distances are 1.33 and 1.54 Å, respectively).
15. Explain the concept of separation of partition
16. Derive an expression for the translational partition function.
17. Draw Jablonski diagram and indicate the difference between fluorescence and phosphorescence. Discuss also their difference with regard to transition (pathways), duration, and change in spin multiplicity.
18. Mention the various factors affecting fluorescence and phosphorescence and discuss any two factors in detail giving one example each.
19. Discuss the principle and working of Uranyl Oxalate Actinometer.
20. Discuss the differences in the kinetics of the two photochemical reactions of H₂ with Cl₂ and H₂ with Br₂.
21. Write Sackur-Tetrode equation and define the terms involved. Also explain how the translational entropy of a gas varies with (a) temperature (b) pressure (3+2)
22. (a) Differentiate fermions and bosons statistically.

(b) Calculate the molar residual entropy of a crystal in which the molecules can adopt

24 orientations of equal energy at 0K.                                                                 (3+2)

 

 

 

Part C

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

 

23. Discuss, with a suitable diagram, the different types of lines produced in the emission spectrum of atomic hydrogen.
24. Derive an expression for the energy of a particle in a one dimensional box on the basis of quantum mechanics.
25. Derive an expression for the most probable distribution on the basis of classical statistics.
26. Discuss the mechanism and kinetics of the photochemical reaction between H₂ and Br₂.
27. Mention the different types of quenching and derive Stern-Volmer equation for bimolecular quenching.                                                                                                             (3+7)
28. Mention any four relaxation techniques and derive an expression for relaxation time for a reaction involving equilibrium A = B (both I order) using temperature-jump method. (2+8)

 

* * * * *

 

SOME USEFUL CONSTANTS:

1. Planck’s constant = 6.625 x 10^-34 Js
2. Boltzmann constant = 1.38 x 10^-23 JK^-1
3. Velocity of light = 3 x 10⁸ ms^-1
4. Avogadro number = 6.023 x 10²³
5. Rydberg constant = 1.097 x 10⁷ m^-1

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