Chem-DSE-3: Chemistry of Colloids and Adsorption — DU B. Sc. Life Science (Chemistry) Previous Year Question Papers

a) Explain, why the surface tension of a solvent is not modified to a large extent in the presence of surface-inactive substances. c) Calculate the Hydrophile-Lypophile Balance (HLB) of a mixture of two emulsifiers coutaining40%surfactantA(HLB=12)and60%surfactant8(ELB=15) e) A colloidal sample shows faster Brownian motion at higher temperature. S.tate the reason. D Determine the gold number if 10 mL of gold sol requires 5 mg of gelatin to prevent coagulation. Q:2 a) What are Macromolecues? What properties of colloids do they show? Why they don't show electrophoresis? b) Why Mgc12 is better coagulant than Kcl for As2S3 sol. Explain on the basis of the S chulze-Hardy rule. c) classify the following sols according to their charge: gold sol, feric hydroxide, gelatin, blood, sulphur, arsenious sulphide. What is the origin & significance of charge on a colloidal particle? Q:3 a) Discuss the process of dialysis and ultrafiltration for purification of colloids with labeled diagram along with respective examples, if any. b) Discuss protein-based functional colloids and their in portance. c) Explain peptization as a method of preparation of colloids. (5,5,5) Q:4 a) Explain optical properties of colloids with emphasis on Tyndall effect. b) Briefly discuss any frve applications of colloids in everyday life & industry. c) What is protective colloid? How does a hydrophilic colloid stabilize a hydrophobic one? Give an account of Gold Number in this context. Q:5 a) Outline the assumptions made during the derivation of Langmuir adsoxption equation and hence derive its equation. b) Discuss how the extent of adsorption varies dn (i) increasing the surface area per unit mass of adsorbent, (ii) increasing the temperature of the system, and (iii) increasing the pressure of the gas. c) The~surface tension of ethanol-wat.er-mixtures follows the equation -where is the molar concentration of ethanol. The temperature is 298 K. Calculate the surface excess of ethanol for a 0.5 mol din 3 solution. Q:6 Write short notes any ffergc of the following options: a) Applicati.on of adsoxption phenomenon in living systems b) Coagulation & Flocculation c) Associated Colloids (with examples & diagram) d) Emulsification by Surfactants