Chem 111 -internal 2002

Universal Science College (B. Sc. Biochemistry) First Semester 2002 Second Term Exam Subject: Physical Chemistry Date: 16 Jan, 2003

Full Marks: 100 Pass Marks: 50 Time: 3 hours Group - A

Answer any three questions. Questions are of equal value. 3 × 14=42 1. Derive a kinetic gas equation. Also Boyle’s law and Graham’s law of diffusion. 2. What do you understand by the term hydrolysis? Show the pH of the aqueous solution of salt of weak acid and a weak base is independent of the initial concentration of the salt. 3. Define order and molecularity of a chemical reaction. Rate of a chemical reaction is found to be proportional to one concentration term only. Find out an expression for the rate constant of this reaction. Also show that half-life of this reaction is independent of the initial concentration of the reactant. 4. What is a reversible process? Explain with examples. Derive an expression for the work done by an ideal gas in an isothermally reversible process. Group B Answer any six questions. Questions are of equal value. 6 × 7 = 42 1. How are root mean square velocity and average velocity related? 2. Calculate the R.M.S velocity of CO2 at 300 ° Celsius. 3. How is surface tension of a liquid determined in a laboratory? 4. What do you understand by electrolytes? Show that the degree of dissociation of a weak electrolyte is inversely proportional to the square root of its initial concentration. 5. Explain briefly the various theories of acid and base. 6. State Le-Chatelier’s principle. Predict the effect of change of concentration, pressure, temperature, volume and catalyst on the equilibrium of the following reaction. 2SO2 (g) + O2 (g) 2 SO3 (g) + 189.4 kJ 7. How does the Heat of reaction vary with temperature? Derive Kirchoff equation in this connection. 8. Explain the following terms. a. System and surrounding b. Extensive and intensive properties Group – C Answer any eight questions. Questions are of equal value. 8 × 2 = 16 1. How is gas liquefied by Faraday’s method? 2. How many atoms are there per unit cell in a body centered cubic arrangement of atoms. 3. Why do real gases deviate from ideal behaviour? 4. Define pH range of an acid-base indicator. Name what is a suitable indicator for the titration of weak acid versus strong base. 5. What is a solubility product? What is the condition of a precipitation in reactions?

6. 7. 8. 9. 10. 11. 12.

What is common ion effect? Why do we acidify the solution of basic radicals before passing H2S into it for determinantion of group II radicals? Define buffer solution. Write an expression showing that the relationship between pOH, pK and concentration of salt and base for buffer solution. What equilibrium constant for the reaction H2 + I2↔2 HI is 49 at 711 k, find the equilibrium constant for the reaction. ½ H2 +1/2 I2↔HI at the same temperature. What is specific reaction rate of a chemical reaction? What is meant by Enthalpy of a system? Why the enthalpy of neutralization of weak acid versus strong base is lower than –13.7 kJ. Define internal energy. ***