LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

WD 01

FIFTH SEMESTER – April 2009

CH 5500 – PHYSICAL CHEMISTRY – II

 

 

 

Date & Time: 16/04/2009 / 9:00 – 12:00    Dept. No.                                              Max. : 100 Marks

 

 

PART – A

Answer ALL questions                                                                                               (10 x 2 = 20)

1. Write calomel electrode reaction as reduction.
2. NaCl cannot be used in salt bridge. Why?
3. E^ocell is 1.10V for Zn + Cu²⁺ → Zn²⁺ + Cu. Calculate ∆G^o cell at 298K.
4. What are concentration cells? Give one example.
5. Define transport number of an ion.
6. 30% of a first order reaction is complete in 100 min. Calculate the rate constant of the reaction.
7. What is the effect of ionic strength on the rate constant of a reaction of the type A^– + B^– →

products in solution phase.

 

8. Mention the steps involved in a thermal chain reaction.

 

9. “Adsorption is spontaneous and mostly exothermic”.
10. Define quantum yield of a photochemical reaction.

PART – B

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

11. Derive Nernst equation for a cell reaction and hence deduce an expression for equilibrium constant for the cell reaction.
12. Calculate E^o cell, Ecell, ∆G^o cell and ∆G cell for Zn|Zn²⁺ (0.01M) ||Ag⁺ (0.01M) |Ag at 298k. E^ored Zn⁺²|Zn – 076V and Ag⁺|Ag 0.8V.  Assume n = 2.  Write the electrode reactions.
13. Write down the electrode reactions in a) lead storage cell   b) H₂ – O₂ fuel cell.  Mention one salient feature for each.                                                                                 (3+2)
14. What is Weston – Cadmium cell? Explain its construction and indicate the electrode reactions.                                                                                                                      (2+2+1)
15. How is transport number of an ion determined experimentally?
16. Explain the variation of equivalent conductance with concentration for
17. a) strong electrolyte b) weak electrolyte in water with suitable graph. (2+2+1)
18. Differentiate order form molecularity.
19. Explain the principle of conductometric titrations with one example.
20. The rate of a first order reaction is doubled on increasing the temperature from 27^oC to 37^oC (R=8.314 JK^-1 mol^-1.)   Calculate the activation energy of the reaction.
21. State the postulates of Langumir adsorption isotherm and hence derive the equation. (2+3)
22. Write briefly on i) photosensitization ii) chemiluminescence.
23. Derive an expression for rate constant of a second order reaction of the type 2A →products.

PART – C

Answer any FOUR questions                                                   (4 x 10 = 40 marks)

23) a) Explain how ∆G^o, ∆H^o, ∆S^o of a cell reaction be determined using EMF measurements.    (6)

1. b) Explain the significance of electromotive series.                 (4)
2. Give an account of any two of the following a) types of electrodes with the relevant Nernst

equations.  b) determination of Ksp of a salt using EMF.  c) Principle for potentiometric acid –

base titrations.  d) standard hydrogen electrode.

25. a) Derive an expression for Ecell for a chemical cell with transference (6)
26. b) How is Ka of weak acid determined using conductance measurements?                         (4)
27. a) Explain any two methods of determining order of a reaction (6)
28. b) Discuss the mechanism of S_N2 reaction with an example. (4)
29. Explain the kinetics of single substrate enzymatic reaction. How are the kinetic parameterms

evaluated?                                                                                                                               (6+4)

28. Write notes on any two of the following (5+5)
29. a) Debye-Huckel theory of strong electrolytes
30. b) Principle of polarography
31. c) Quinhydrone electrode & its use.
32. d) Parallel reactions.

 

 

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      LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

WD 09

THIRD SEMESTER – April 2009

CH 3500 – PHYSICAL CHEMISTRY – I

 

 

 

Date & Time: 06/05/2009 / 9:00 – 12:00  Dept. No.                                                   Max. : 100 Marks

 

 

 

PART – A

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

 

1. Distinguish C_p and C_v of an ideal gas.
2. Define: Integral heat of dilution.
3. Deduce the relationship between K_p and K_c for the following reaction

2NO(g) + O₂(g)     2NO₂(g)

4. Dissociation of NH₄Cl is represented by the equation

2NH₄Cl(s)      NH₃(g) + HCl(g)

What is the number of components for it if a start is made with (i) pure NH₄Cl    (ii) NH₄Cl  and either product of dissociation

5. State Le Chatelier’s principle.
6. Apply phase rule to the triple point of water.
7. State Hess’s law of heat of summation.
8. Calculate the root mean square velocity of O₂ molecule at 27°C.
9. “Addition of a non-volatile solute lowers the vapour pressure of a solution” – Offer a theoretical explanation for this statement.
10. State the Nernst distribution law.

PART – B

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

 

11. Show that the entropy of mixing of ideal gases is positive.
12. The standard enthalpy of formation of HCl gas at 25°C is -22.06 kcalmole^-1. Calculate the ΔE of formation at 25⁰C.
13. State third law of thermodynamics. Explain how the absolute entropy of a substance can be determined on the basis of the third law of thermodynamics.
14. State and derive Gibb’s phase rule.
15. Water gas reaction is represented by the equation

C_(s) + H₂O_(g)     CO_(g) + H_2(g)

1. What is the equilibrium law expression for the reaction?
2. State, giving reasons, how this equilibrium will shift if
3. all pressures are doubled
4. the temperature is increased

 

16. Deduce gas laws on the basis of the kinetic theory of gases.
17. State and explain Henry’s law. What are the limitations of this law?

 

 

 

 

18. What is meant by critical solution temperature? How can it be determined for phenol-water system? Explain the effect of addition of NaCl on the critical solution temperature.
19. How can the molecular mass of a nonvolatile solution be determined from freezing point measurements?
20. A 0.1formal solution of NaCl is found to be isotonic with a 1.10% solution of urea. Calculate the apparent degree of dissociation of NaCl.
21. Apply phase rule to Lead-Silver system and discuss the desilverisation of lead from this system.
22. Draw and explain the phase diagram of any three component system having one partially miscible pair.

PART – C

Answer any FOUR questions                                                                         ( 4 x 10 = 40 marks)

 

23. Derive Maxwell’s equations from basic thermodynamic ralations.
24. a. Derive Gibbs-Helmholtz equation.
25. The measured heats of neutralization of acetic acid, formic acid, hydrocyanic acid and hydrogen sulphide are 13.20, 13.40, 2.90 and 3.80 kcal per geq. respectively. Arrange these acids in the decreasing order of strength.
26. Draw the phase diagram of FeCl₃-H₂O system and describe its complete labeling. Explain, What do you understand by the isothermal evaporation of the solution.
27. a. State and explain Raoult’s law.
28. What are azeotropic mixtures? Give examples.
29. a. What are abnormal colligative properties? How will you calculate the vant Hoff factor and degree of dissociation of a solute from the measurement of colligative properties?
30. 0.9g of a solute was dissolved in 100ml of benzene at 25°C when its density is 0.879g/ml. The solution boiled 0.250°C higher than the boiling point of benzene. Molal elevation boiling point constant for benzene is 2.52 Kkgmol^-1. Calculate the molecular weight of the solute.

 

28. Derive thermodynamically the relation connecting elevation in boiling point of a solution of a non-volatile solute in a volatile solvent and its molality.

 

 

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