LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – APRIL 2011

CH 3504 – THERMODYNAMICS

Date : 25-04-2011              Dept. No.                                                  Max. : 100 Marks

Time : 9:00 – 12:00

PART – A

Answer ALL questions                                                                                  (10 × 2 = 20marks)

1. Among the different states of matter, which state has the maximum entropy? Why?

1. State Le Chatlier-Braun principle

1. Why is Cp greater than Cv?

1. Define Joule – Thomson coefficient.

1. Give the units of entropy and enthalpy.

1. If the equilibrium constant is 1000atm for the forward reaction, what will be its value for the backward reaction?

1. Define standard free energy of formation.

1. What is the ΔH value for a strong acid strong base neutralisation reaction?

1. State the II law of Thermodynamics on the basis of Carnot’s cycle.

1. 5moles of an ideal gas expand reversibly from a volume of 8dm3 to 80 dm3 at a temperature of 27 Calculate the change in entropy.

PART – B

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

1. Prove that Cp – Cv = R. (5)

1. Differentiate extensive property from intensive property. (5)

1. Calculate W and ΔU for the conversion of 1mole of water at 100˚C to steam at 1 atm pressure. The heat of vaporisation of water at 100˚C is 40670J/mol.         (5)

1. State Hess’s law of constant heat of summation and explain its application. (2+3)

1. How is the enthalpy of combustion measured? Explain.       (5)

1. (a)Calculate the maximum efficiency of an engine working between 110˚c and 25˚c.

(2)

(b)Calculate the entropy change in the melting of 1Kg of ice at 0˚c. Heat of fusion of ice
is 334.72J/g.                                                                                                                            (3)

1. Derive the equation for the entropy of mixing of gases.  (5)

1. Derive the relation between ΔA and Wrev.       (5)

1. Derive the relation between Kp and Kc for a reaction.       (5)

1. Explain the effect of pressure and temperature in the formation of ammonia gas

from nitrogen and hydrogen.                                                                                                     (5)

1. Calculate Kp at 25˚c and 325˚c for the reaction NO(g) +1/2 O2NO2(g) if at 25˚c

ΔH = -56.48KJ/mol and ΔG = -34.85KJ/mol.                                                                       (5)

1. 22. Derive Kp for the reaction N2O42NO2 (g).                                                                          (5)

PART – C

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

1.   a) Derive Kirchoff’s equation.

1. b) Derive any one Maxwell equation.               (5+5)

1. 24. (a) Calculate the ∆H for the reaction AgNO3 + NaCl →NaNO3 +AgCl.

Given  Ag+(aq)= -105.9KJ/mol, AgCl(s)= -127.0KJ/mol,

Cl(aq)= -167.5KJ/mol.

(b) Differentiate bond energy from bond dissociation energy.                                     (5+5)

1. a) Derive Gibbs Helmholtz equation.                             (6)

1. b) Explain its application.      (4)

1. Derive Clausius- clapeyron equation and explain its application in Liquid Vapour

equilibrium.                                                                                                                             (5+5)

1. Derive van’t Hoff isotherm equation.

Hence deduce an expression for equilibrium constant.                                                   (5+5)

1. (a) State and explain III law of thermodynamics.         (5)

(b) How is standard entropy of oxygen gas evaluated?                                                       (5)

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