Chem 111-final 2005

(B. Sc. Biochemistry) First Semester 2006 Subject: Chem 111 (Physical Chemistry)

Full Marks: 100 Pass Marks: 45 Time: 3 hours

Candidates are required to give their answers in their own words as far as practicable. The figure in the margin indicates full marks. Group (A) Long Questions (Any three)

(3× ×14 = 42)

Group (B) Short Questions: (Any six)

(6× ×7 = 42)

1. Stating postulates derive a kinetic gas equation. Calculate the critical temperature of a van der waal’s gas for which critical pressure is 100 atm and vander waal constant b is 50 cm3 mol-1. 2. Discuss the Debye- Huckel theory of strong electrolytes. A solution containing 0.00839 gm of silver nitrate per gram of water was electrolyzed between silver electrodes. During the experiment, 0.088 gm. of silver was deposited in a silver coulometer placed in series. What are the transport numbers of Ag+ and NO3- ions? 3. Define pseudo- order reactions. Derive an expression for second order integrated rate equation when the initial concentrations of the two reactants are different. 4. A first order reaction is 15% complete in 30 minutes. How long will it to take to be 75% complete. Derive Clausius – Clayperon equation. Calculate the standard entropy of formation of CH4 (g) in cal mol-1 K-1 if the standard entropies of CH4( g), C(s) and H2 (g) are 186.2 , 5.74 and 130.6 J mol-1K-1 respectively. 1. Show that the excluded volume is approximately equal to four times the actual volume of gas molecules. 2. Explain electrophoresis mentioning its application. 3. State and explain Ostwald dilution law. 4. How is transport number of ion determined using Hittorf’s method? 5. Explain collision theory of bimolecular reactions. Mention its weakness. 6. Derive Arrhenius equation. 7. Derive an expression for entropy of mixing. 8. Define entropy. State and explain the second law of thermodynamics.

Group (C) Very Short Questions: (Any eight)

(2× ×8 = 16)

1. Define mean free path and collision frequency. 2. What is the effect of addition of an electrolyte to Hydrophobic sol? 3. Define gold number. The gold numbers of A, B, C and D are 0.005, 0.05, 0.5 and 5 respectively. Which of these has the greatest protective action? 4. Why the equivalent conductance of a solution of a strong electrolyte gradually increases with dilution and ultimately assumes a limiting value? 5. 0.5 N NaCl placed between two electrodes 1.5 cm apart and having an area of each 3.0 cm2 offered a resistance of 25.0 ohms. Calculate the equivalent conductance.

6. Find out the ionic strength of the mixture of 0.1 M FeCl3 and 0.01 M KCl solution. 7. Why high order reactions are rare? 8. What are the characteristics of enzyme catalysis? 9. What is specific reaction rate? 10.State third law of thermodynamics. 11.Define chemical Potential. 12.Three moles of an ideal gas expand isothermally from 1 litre to 10 litre at 300 K. Calculate the change in free energy of the gas( R= 8.314 JK-1 mol-1).