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)**

** **

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

** **

- State Le Chatlier-Braun principle

** **

- Why is C
_{p}greater than C_{v}?

** **

- Define Joule – Thomson coefficient.

** **

- Give the units of entropy and enthalpy.

** **

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

** **

- Define standard free energy of formation.

** **

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

** **

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

** **

- 5moles of an ideal gas expand reversibly from a volume of 8dm
^{3}to 80 dm^{3}at a temperature of 27^{◦}Calculate the change in entropy.

** **

__PART – B__

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

** **

- Prove that Cp – Cv = R. (5)

** **

- Differentiate extensive property from intensive property. (5)

** **

- 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)

** **

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

** **

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

- (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)

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

- Derive the relation between ΔA and W
_{rev}. (5)

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

- Explain the effect of pressure and temperature in the formation of ammonia gas

from nitrogen and hydrogen. (5)

- Calculate Kp at 25˚c and 325˚c for the reaction NO(g) +1/2 O
_{2}NO_{2}(g) if at 25˚c

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

**22**. Derive Kp for the reaction N_{2}O_{4}2NO_{2}(g). (5)

__PART – C__

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

** **

- a) Derive Kirchoff’s equation.

- b) Derive any
__one__Maxwell equation. (5+5)

**24**. (a) Calculate the ∆H for the reaction AgNO_{3}+ NaCl →NaNO_{3}+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)

- a) Derive Gibbs Helmholtz equation. (6)

- b) Explain its application. (4)

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

equilibrium. (5+5)

- Derive van’t Hoff isotherm equation.

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

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

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

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