classes_Spring08_172ID39_final2007_solutions

classes_Spring08_172ID39_final2007_solutions - Chemistry...

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1 Chemistry 172/273 Final exam June 12, 2007 Spring 2007 Total: 235 points 1. (20 points) a) Nanocrystallites of CdSe, sometimes referred to as “quantum dots” can be stabilized with a reagent that binds to the Cd atoms at the particle surface. Choose two of the following reagents that are most likely to stabilize the surface: i) CH 3 (CH 2 ) 7 S - ; ii) CH 3 (CH 2 ) 7 O - ; iii) HSCH 2 CH 2 SO 3 - ; iv) CH 3 (CH 2 ) 7 CO 2 - ; v) Cl - . b) If they are properly stabilized, CdSe nanoparticles are photoluminescent, giving off visible light when stimulated with UV light. Alfredo Sanz-Medel and coworkers have reported ( Chem. Commun . 2005 , 883) that the luminescence spectrum of stabilized CdSe nanoparticles can be quenched in the presence of certain ions. If one assumes that the quenching process occurs due to binding of the quencher to the CdSe surface, which of the following ions tested would be expected to result in quenching: SO 4 2- , SO 3 2- , NO 2 - , NO 3 - , SCN - , Cl - , Br - , I - , CN - , acetate?
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2 2. (20 points) One possible distortion of an octahedral complex is to become tetragonal, where
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This note was uploaded on 10/12/2009 for the course CHEM C172 taught by Professor Zink,j during the Spring '08 term at UCLA.

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classes_Spring08_172ID39_final2007_solutions - Chemistry...

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