chm325h-m2009 - UNIVERSITY OF TORONTO Faculty of Afts and...

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Unformatted text preview: UNIVERSITY OF TORONTO Faculty of Afts and Science FINAL EXAMINATION 2009 CHEM 325HS DURATION: 120 MINUTES NO AIDS ALLOWED NOTE THAT CLEAR DIAGRAMS AND CONCISE INFORMATIVE ANSWERS ARE ESSENTIAL FOR SCORING HIGH MARKS IN THIS EXAMINATION ANSWER QUESTIONS IN SECTION A AND B IN SEPARATE EXAMINATION BOOKS TOTAL MARKS: 120 Page 1 of 3 SECTION A ANSWER QUESTIONS 1-4 TOTAL 60 MARKS 1. (15 marks) Write the overall chemical reactions involved in the polymerizations that form nylon-8,12; poly(propylene terephthalate); and poly(vinyl acetate). Draw the structures of the resulting repeating unit. 2. (15 marks) Explain how IR-spectroscopy can be used to characterize the following polymer characteristics: (a) hydrogen bonding, (b) miscibility with another polymer, (c) chemical degradation. Give appropriate examples and draw schematic diagrams of the corresponding spectra. 3. (15 marks) Polystyrene (PS) is a brittle polymer; therefore, films formed from PS show low impact strength. Describe at least 2 methods to improve the mechanical properties of PS. In each case, explain the reason of enhancement of the mechanical properties and give appropriate equations where possible. 4. (15 marks) Explain your approach to selecting an appropriate solvent for polydimethylsiloxane. Support your answer by appropriate equations. Page 2 of 3 SECTION B ANSWER 3 QUESTIONS FROM QUESTIONS 1-6 TOTAL 60 MARKS l. 2. (20 marks) Explain in detail why Prussian Blue, Fe4[Fe(CN)6]3, is blue? (20 marks) Explain the effect of temperature on the structure, bonding and electrical conductivity of Rutile-type transition metal dioxides TiOz, V02, NbOz and M002? (20 marks) Explain the origin and nature of the metal-nonmetal transition and incommensurate charge density wave (AF = 2.35a) observed in the oxidized form of Krogmann’s salt Kth(CN)4Br0.3~3H20, where a is the normal lattice spacing for the un-oxidized form of Krogmann’s salt Kth(CN)4-3H20, that is the PtH-Pt distance between square planar [Pt(CN)4]2‘ building blocks. (20 marks) Explain how you would synthesize and explain the physicochemical underpinnings of a Schottky—type semiconductor-metal junction solar cell, based on a thin film of a soluble polyacetylene derivative deposited on an n-doped silicon substrate, nSi-[(CH)1_X(CR)X], where R is an organic substituent that replaces some of the hydrogen’s in normal polyacetylene (CH)X. Elaborate why you would prefer this kind of solar cell over one based upon either a thin film of polyacetylene deposited upon an n-doped silicon substrate nSi—[(CH)X] or gold deposited on an n—doped silicon substrate, nSi-Au? (20 marks) Provide synthesis and structure, bond and band, molecule and polymer material relations between S4N4 and SzNz and (SN)X that enables you to rationalize the low temperature superconductivity of polythiazyl (SN)X. (20 marks) Give a detailed explanation for why ZrSz and M082 behave as semiconductors yet Nb82 acts like a metal? Page 3 of 3 ...
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