LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

GH 51

SECOND SEMESTER – APRIL 2008

CH 2800 – THERMODYNAMICS

 

 

 

Date : 21/04/2008            Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

                                                                      PART – A

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

 

1. Show that chemical potential m_I = ½p,s,h_j
2. State the thermodynamic condition for a system to be in phase equilibrium.
3. The density of N₂(g) at 273 K and at 1.013 ´ 10⁵ pascal pressure is 1.25g/l. Calculate the fugacity of N₂ at 0° C and 100 atm pressure.   (1 atm = 1.013 ´ 10⁵ pascal)
4. Deduce the expression for the mean activity coefficient (g±) in a terms of molality and activity of the solute for the solution of Ce₂(SO₄)₃.
5. The dissociation pressure (p) of Ag₂O(s) to form Ag(s) and O₂(g) is given by the equation

log₁₀P = –   + 3.5 where p is in atmosphere.

Evaluate the decomposition temperature of Ag₂O(s).

6. What is meant by residual entropy?
7. Deduce the relation between entropy and thermodynamic probability.
8. Calculate the ratio of translational partition function for He(g) to Ne(g) at 25°C, 1 atm. pressure.
9. Calculate the number of ways of distributing 5 particles among six energy levels if they obey Pauli’s exclusion principle.
10. What are macro and microstates?

 

PART – B

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

 

11. Explain how the activity of a system depends on (i) Temperature (ii) pressure
12. The volume of sodium bromide – water solution as a function of molality (m) at constant temperature and pressure is given by the expression

V = 1003 + 23.2 m + 2.2 m^3/2 – 0.18 m²

Determine the partial molal v9olumes of NaBr and H₂O for a 0.25 m solution.

13. Draw the phase diagram of a three component system with two solids (A, B) and liquid (C ),  explain in which both the solids form salt hydrate.

 

 

 

 

 

 

 

 

14. Derive an expression for for a gas with the equation of state.

where B, C are constants which are functions of temperature only.

15. Derive Gibb’s-Duhem equation.
16. Explain how absolute entropy of a gas like Cl₂ at 300 K be determine using III law of thermodynamics.
17. Write Sackukr-Tetrode equation and explain the terms. What is its use?
18. Evaluate the rotational partition function for CO(g) at 27°

(I = 14.5 ´ 10^-47 kg m²).

19. How is equilibrium constant of a reaction calculated using statistical mechanics.
20. The electronic ground state of monoatomic gas is four fold degenerate and the first electronic excited state is 400 cm^-1 above the ground level. Evaluate the electronic partition function at 2000 K if the first excited state is two fold degenerate.
21. Derive an expression for (C_v)_vib of a gaseous system.
22. Compare the three statistical distributions and explain.

 

 

PART – C

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

23.(a) Derive any two Maxwell equations.

(b) Draw the phase diagram of a simple eutectic system and explain.

24.(a) Derive expressions for q, DG, DH for isothermal reversible expansion of a

vander Waal’s gas.

(b) The equilibrium constant of a reaction at 273 K is 10⁸ and 10⁶ at 310 K.
Evaluate DH° for the reaction and mention the assumption involved.

25. Explain how the activity coefficient be evaluated using EMF method with a suitable example.
26. State the postulates of Maxwell-Boltzmann distribution and deduce an expression for most probable distribution.
27. Explain Debye’s theory of heat capacity of solids and compare it with other theories.
28. Explain any two of the following.

(a) Separation of partition function

(b)Statistical formulation of ARRT

(c)Application of Quantum Statistics with reference to thermionic emission

(d)Equipartition principle

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