LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
B.Sc. DEGREE EXAMINATION – CHEMISTRY
THIRD SEMESTER – SUPPLEMENTARY – JUNE 2012
CH 3504/CH 3500 - THERMODYNAMICS
Date : 27-06-2012
Time : 2:00 - 5:00
Dept. No.
Max. : 100 Marks
PART A
Answer all questions
10 × 2 = 20marks
1. Define Internal energy.
2. What is Cp ? Write its unit.
3. What is an endothermic process?
4. Calculate Δn for the reaction N2(g) + 3H2(g)
2NH3(g).
5. Write down the limitations of the First Law of Thermodynamics.
6. Define efficiency of a heat engine.
7. State Law of Mass action.
8. The value of Kp for the reaction A(g) + B(g)
the reaction
C(g) + D(g) is 1.06 x 105at 250C. Calculate ΔG for
9. What is LeChatlier – Braun principle.
10. Give any one statement of the third law of thermodynamics?
PART B
Answer any EIGHT questions.
8 × 5 = 40marks
11. Explain the postulates for the kinetic theory of gases.
(5)
12. Calculate the pressure exerted by one mole of CO2 in a 1.32 dm3 vessel at 480C using
Vanderwaals Equation. The vanderwaals constant a = 3.59 dm6 atm  mol2 &
b = 0.0427dm3 / mol.
(5)
13. Derive an expression for work done in an isothermal expansion of an ideal gas.
(5)
14. (a) Calculate the enthalpy of combustion for Methane at 250c and 1 atm pressure.
ΔHf0(CO2) = 393.5KJ/mol, ΔHf0(H2O) = 285.9KJ/mol, ΔHf0(CH4) = 74.8KJ/mol .
(g)
( )
(g)
(b) What is E for the above reaction.
15. What is Joule – Thomson coefficient? Explain its significance.
(3)
(2)
(2+3)
16. The heat supplied to a Carnot engine is 1897.8KJ. How much useful work can be done
by the engine which works between 00c and 1000c. What is its efficiency?
17. Calculate the change in entropy accompanying the heat change for one mole of Helium gas,
assumed Ideal from 298K to 1000K at constant pressure. Assume that Cv = 3/2 R.
(5)
18. Deduce an expression for the variation of free energy change with a) temperature and
b) pressure.
(3+2)
19. The equilibrium constant Kp for the reaction H2(g) + S(g)
H2S(g) is 20.2 atm-1 at 9450C &
9.1 atm-1at 1.0650C. Calculate ΔH0. What is Kc for the reaction at 945 C.
20. Explain the effect of 1) pressure
equilibrium.
2) temperature on N2(g) + 3H2(g)
2NH3 (g) at
21. Differentiate bond energy from bond dissociation energy with an example.
22. Explain Nernst Heat theorem.
PART – C
Answer any FOUR questions
4×10 = 40 marks
23. Derive Maxwell relations.
(4x2.5)
24. (a) Explain how the enthalpy of combustion is determined using Bomb Calorimeter.
(b) Derive Kirchhoff equation.
(5 + 5)
25. a) Derive Gibbs Helmholtz equation and discuss its application.
b) Explain the physical significance of free energy change.
(5+5)
26. Derive VantHoff equation dlnKp/dT = ΔH0/RT2 and hence deduce the relationship between Kp
and Temperature.
(10)
27. a) Derive thermodynamically the relation between Cp and Cv .
b) Derive an expression for Kp for N2O4(g)
2NO2(g).
28. How is absolute entropy of O2 (g) determined using III law of thermodynamics.
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(6)
(4)