Polymers, Colloids, Surfaces, and Interfaces — DU B.Sc (hons) Chemistry Previous Year Question Papers

1. (a) How are polymers classified on the basis of molecular forces ? (b) Explain mechanism of coordination polymerization using an example. (c) Discuss the kinetics of condensation polymerization. What are its unique features ? 5,5,5 (b) Explain the two distinguishable modes of solvent diffusion into a polymer. Write the complete Flory-Huggins equation for the Gibbs free energy change. Identify the entropic and enthalpic terms within the equation and explain the role of the interaction parameter. 5,5,5 Write short notes on : (a) Emulsion polymerization (b) Ionic polymerization (c) Upper Critical Temperature (UCLT) in polymer-solvent systems. 5,5,5 (a) (b) (c) (a) (b) What do you understand by the electrical double layer of colloids ? Explain its structure with the help of a properly labelled diagram. Explain the terms coagulation and flocculation. Suggest any two methods to bring about the coagulation of a colloidal suspension. Given two unknown samples of oil-in-water (O/W) and water-in-oil (W/O) emulsions, how will you distinguish between them ? 5,5,5 Explain the phenomenon of capillarity. Give the capillary rise equation and explain the effect of tube radius, surface tension of liquid and density of liquid on capillarity. What are aerosols ? How are the colloidal properties of aerosols different from those of other colloid like emulsions and sols. (c) How is the molecular behaviour of solid surfaces different from liquid surfaces ? 5,5,5 What is the effect of pressure of gas on the extent of adsorption ? Explain using the Freundlich adsorption isotherm. What are the differences between macromolecular and associated colloids ? Explain any two dispersion methods of preparation of lyophobic colloids. 5,5,5 Describe the two morphological classes of foams with the help of suitable diagrams. Briefly explain the Gibbs-Marangoni effect. What are Gibbs films ? Explain the Gibbs adsorption isotherm and its role in determining surface activity of a substance. Briefly explain the microscopic mechanisms that contribute to adhesion. 5,5,5 Explain the role and application of colloid chemistry in the following : (a) Petroleum recovery (b) Delta formation (c) Sewage disposal. 5,5,5