LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – APRIL 2012

CH 3504/CH 3500 – THERMODYNAMICS

 

 

 

Date : 19-04-2012              Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

 

PART – A

Answer ALL the questions:                                                                                 (10 x 2 = 20 marks)

1. What is work function? How is it related with internal energy?
2. What is meant by Joule-Thomson effect?
3. Define heat of transition.
4. What is integral heat of dilution?

5. Calculate the maximum efficiency of a Carnot engine operating between 27°C

and 127°C.

1. What is entropy? What are the units of entropy?
2. State the law of mass action.
3. Define the term “equilibrium constant”.

9. State first law of thermodynamics.
10. Mention the essential conditions for spontaneity in a chemical reaction.

 

PART – B

Answer any EIGHT of the following:                                                                 (8 x 5 = 40 marks)

 

11. The enthalpy of reaction (DH) for the formation of ammonia N₂ + 3H₂ ⇌ 2NH₃ at 27°C was found to be -94 KJ. What will be the enthalpy of reaction at 50°C. The molar heat capacities at constant pressure at 27°C for N₂, H₂ and NH₃ are 28.45, 28.32 and 37.07 joules respectively.
12. What are exact differentials? Explain with conditions and examples.
13. Bring out the relationship between C_p and C_v.
14. State and explain Hess’s law.
15. Deduce an expression for the entropy of mixing of ideal gases.
16. Explain the need for Second law of Thermodynamics.
17. Explain the postulates of the kinetic theory of gases.
18. Derive any two Maxwell relations.
19. For a water gas reaction at 1000 K the standard Gibb’s energy change is

-8.1 kJmol-1. Calculate the value of equilibrium constant.

 

 

20. Derive the expressions for K_p for decomposition of PCl₅.
21. Predict whether the reaction CO_(g)  + H₂O_(g)   →  CO_2(g)  + H_2(g) is spontaneous or

not. The standard free energies of formation of CO_(g), H₂O_(g) and CO_2(g) are

-137.27, -228.6 and -394.38 kJ mol^-1 respectively.

22. Explain Nernst heat theorem.

 

PART – C

 

Answer any FOUR of the following:                                                                  (4 x 10=40 marks)

 

23. a) Compare isothermal and adiabatic reversible expansion of ideal gases.
24. b) Derive an expression for the variation of enthalpy change of reaction with

temperature.

24. a) Calculate the bond energy of C – H bond in methane from the following data:
25. C_(s) + 2H_2(g)   →  CH_4(g)    ∆H = -74.8 kJ
26. H_2(g) →  2H_(g)                    ∆H = 435.4 kJ

iii. C_(s)   →  C_(g)                        ∆H = 718.4 kJ

1. b) How is enthalpy of combustion measured?
2. a) Describe in details the carnot cycle for establishing the maximum convertibility

of heat into work.

1. b) Explain the thermodynamic principle of the working of refrigerator.
2. a) Derive Gibbs-Helmholtz equation.
3.  b) Discuss the effect of temperature, pressure and concentration on the reaction

for the formation of ammonia.

27. a) Derive: (i)   Vant Hoff isothrm

(ii)  Van derwual’s equation.

 

28.    a) State and explain III law of thermodynamics.
29.     b) How is the standard entropy of oxygen gas evaluated?

 

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – NOVEMBER 2012

CH 3504/3500 – THERMODYNAMICS

 

 

Date : 15/11/2012             Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

 

 

 

PART – A

 

Answer ALL questions:                                                                                           (10 x 2 = 20 marks)

 

1. Define isothermal and isobaric processes.
2. Define the adiabatic process.
3. What is meant by calorific value?
4. Define heat of transition.
5. What is the need for the second law of thermodynamics?
6. Define the term efficiency of an engine.
7. State the law of mass action.
8. What is a homogenous mixture?
9. Give the Van’t Hoffs isotherm. Explain the terms.
10. What are the exceptions to third law of thermodynamics?

 

PART – B

 

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

 

11. Derive Vander Walls equation of state.
12. Compare W_rev and W_irrev.for an isothermal process.
13. Derive the Kirchoff’s equation.Give its application.
14. State Hess’s law of constant heat of summation and explain its application.
15. For a certain gas C_p = 8.58. J mol^-1 Two moles of the gas are expanded adiabatically from an initial

temperature of 20^oC to  a final temperature of -45.4^oC.   Calculate the work done.

16. Explain the method for the determination of enthalpy of combustion.
17. Explain the thermodynamic principle of the working of refrigerator.
18. Derive the equation for the entropy of mixing of gases at constant temperature.
19. Derive the relationship between K_p and K_c.
20. Derive Van’t Hoffs isochore.
21. Discuss the dissociation of ammonia by applying Le-chatlier principle.
22. Explain the Nernst heat theorem.

 

 

 

PART – C

 

Answer ANY FOUR questions:                                                                                   (4 x 10 = 40 marks)

 

23. a) Explain the postulates of the kinetic theory of gases. (5)
24. b) Discuss Joule Thompson effect.                                                                      (5)

 

24. a) Discuss the thermodynamics of Carnot cycle.                                                (5)
25. b) Explain the bond energy.                                                                                (5)

 

25. a) Derive Gibbs Helmholtz equation. (5)
26. b) Discuss the criteria for spontaneous process.                                                  (5)

 

26. a) Explain the properties of equilibrium constant. (5)
27. b) Calculate the equilibrium constant for a equilibrium reaction at 310K

whose  DG^o  value at this temperature is  30 kJ mol^-1.                                    (5)

 

27. a) Apply law of mass action for the formation of HI. (5)
28. b) Explain the factors which alter the state of equilibrium for the above

reaction.                                                                                                          (5)

 

28. a) Explain Lewis Randall formulation of third law. (5)
29. b) How will you determine the absolute entropy of oxygen gas?                      (5)

 

 

 

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