Interfaces, Macromolecules, and Biophysical Chemistry — DU B.Sc (hons) Chemistry Previous Year Question Papers

(b) Answer any 4 (four) questions. (a) Why are surfactants known as surface-active agents? Discuss micellization and factors that influence the micellization process. (b) How do we calculate the thermodynamics parameters of micellization of surfactant through conductivity measurements? (c) What is pgicking parameters ? How does packing parameter defines the shape of micelles ? (d) How does critical micelle concentration (CMC) affect : (i) Surface tension and (a) Differentiate between : (i) Adsorbent and adsorbate. (ii) Physisorption and chemisorption. (iii) Langmuir adsorption isotherm and Brunauer-Emmett-Teller (BET) adsorption isotherm. (b) Explain the determination of Surface area of surfactant molecule by Gibb's adsorption isotherm. (c) What is capillary electrophoresis ? State its advantages over traditiorial electrophoresis. Discuss how does isoelectric point help in separation of mixture of proteins ? (d) What is chromatography ? Discuss basic principles of ion exchange chromatography and size exclusion chromatography for separation of biological samples like amino acids and protein. (a) Differentiate between amorphous and crystalline `polymers ? How does : (i) Polymer's chain flexibility and (ii) molecular forces affects glass transition temperature (Tg). (b) Discuss the fonowing polymerization reaction : (i) Addition polymerization ofpolypropylene (ii) Condensation polymerization of polyethylene terephthal.ate (PET). (c) What are factors that influences polymer crystallinity ? Discuss how the polymers' crystallinity affects its properties. (d) A polydisperse sample of polyethylene is prepared by mixing three monodispersed samples in the following propertions. Using this information calculate the number average molecular weight, Mn, weight average molecular weight Mr and the polydispersity Index (PDI) of the polymer. (a) Discuss electronic Circular Dichroism (ECD) and vibration Circular Dichroism (VCD) ? State the advantage of VCD over ECD and how VCD help in analysis of biological samples like Deoxyribonucleic acid (DNA) and Protein. (b) An intrinsic viscosity (n.) of polymeric solutions of polyvinyl alcohol (PVA) through viscometry method was found to be 200 cm'/gm, the Mark- Houwink constant K is 3.6 × 102 and empirical constant (a) is 0.64. What will be its viscosity average molecular weight (M.) ? (a) A surfactant molecule at critical micelle concentration (CMC) forms a micelle whose diameter is measures as 8 nm and the area of head group of surfactant molecule is 0.3 nm2. Calculate the number of surfactants forming the micelle. (d) What is adsorption isotherm ? Discuss Type 11, Type IV BET adsorption isotherm. (a) What are enzymes ? Define e`nzymes catalysis and give one suitable example of it ? For an enzyme catalytic reaction prove that at low concentration the rate of reaction is first order reaction. (b) What is specificity constant in enzyme catalytic reaction and state its significant ?