Chem 111 -final 2002

(B. Sc. Biochemistry) First Semester 2002 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. What do you understand by coefficient of viscosity? What is its unit? How is viscosity of a liquid measured in a laboratory? 2. What are electrolytes? How are they classified into certain group? Show that degree of ionization of weak electrolyte is inversely proportional to the square root of initial concentration of the electrolyte. 3. Derive a second order rate equation for the reaction 2A Product Show that half-life period depends upon initial concentration of the reactants. 4. What is a reversible process? Distinguish it with an irreversible process. Derive an expression for the work done by an ideal gas in an isothermally reversible process.

1. How are root mean square velocity and average velocity related? 2. Calculate the average speed of Nitrogen gas at NTP (M=14). 3. Why can’t we determine the end point of the titration of weak acid versus weak base using acid base indicators? 4. Define and explain the following: i. Plane of symmetry ii. Center of symmetry iii. Space lattice and unit cell 5. What is Le-Chateliar’s principle? Apply this principle to find out the favorable conditions for temperature, concentration and pressure for the formation of more SO3 in the following reaction: 2SO2 (g) + O2 (g) 2SO3 (g) + 189.4 KJ 6. If a unimolecular reaction is one quarter completed in 100 minutes, what is the specific rate constant K and half-lie period? 7. Explain the following terms: i. System and surrounding ii. Extensive and intensive properties 8. Calculate the work of expansion of one mole of an ideal gas at 25°C under isothermal conditions, the pressure being changed from 1 to 5 atm.

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

1. What happens to most probable velocity with increase in temperature? 2. What are the causes of deviation of gases from ideal behavior? 3. How does the pressure cooker take lower time for cooking? 4. How many atoms are there per unit cell in a body centered cubic arrangement of atoms? 5. What is the suitable indicator for the determination of end point during the titration of strong acid versus strong base and why? 6. What is meant by buffer capacity? 7. What is Henderson Hasselbalch equation? Write its one application. 8. Give the difference between order and molecularity of reaction. 9. What do you understand by the term thermodynamics? 10. Under what conditions H = E for a chemical reaction? 11. Give one example of a pseudo-unimolecular reaction of first order. 12. What type of system the following systems are? i. A cup containing hot tea ii. Hot tea placed in a china tea pot

(2× ×8 = 16)