UMD CHEM 425 - sample_1_o15 (10 pages)

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sample_1_o15



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sample_1_o15

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Pages:
10
School:
University of Maryland, College Park
Course:
Chem 425 - Instrumental Methods of Analysis

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INSTRUMENTAL METHODS OF ANALYSIS MID TERM EXAM II XXX 125 Points CALCULATIONS 60 Points 1 30 pts The chelate CuA22 exhibits maximum absorption at 480 nm When the chelating reagent is present in at least a 10 fold excess the absorbance is dependent only upon the analytical concentration of Cu II and conforms to Beer s law over a wide range A solution in which the analytical concentration of Cu2 is 2 30x10 4 M and that for A2 is 8 60x10 3 M has an absorbance of 0 690 when measured with a 1 00 cm cell at 480 nm A solution in which the analytical concentrations of Cu2 and A2 are 2 3x10 4 M and 5 00x10 4 M respectively has an absorbance of 0 540 when measured under the same conditions Use this information to calculate the formation constant K for the reaction Cu2 2 A2 CuA22 2 20 pts The fluorescence lifetime of a compound without quenching is 6 0 ns while with a quencher concentration of 1 00x10 2 M the fluorescence lifetime is 2 0 ns The rate constant Page 1 of 10 for intersystem crossing is 1 00x108 s 1 while that for internal conversion from S1 to S0 is negligible Calculate A the rate constant for fluorescence kr B the quenching rate constant kq C the Stern Volmer quenching constant K kq units of M 1 D the fluorescence quantum yield of the quenched compound 3 10 pts Calculate the resolution required for a mass analyzer to resolve peaks for a CH2N MW 28 0187 and N2 MW 28 0061 Page 2 of 10 b C2H4 MW 28 0313 and CO MW 27 9949 INSTRUMENTS 25 points 4 A 5 pts Provide a block diagram of a photodiode array UV Vis absorption spectrophotometer clearly labeling each of the components Page 3 of 10 B 5 pts Provide a diagram of a monochromator clearly labeling each of the components C 5 pts Provide a block diagram of a scanning spectrofluorometer clearly labeling each of the components Page 4 of 10 D 5 pts Provide a block diagram of a capillary electrophoresis system clearly labeling each of the components E 5 pts Provide a block diagram of a double beam scanning UV Vis spectrophotometer clearly labeling each of the components Page 5 of 10 SHORT ANSWERS 40 points Mass Spectrometry 10 points 5 A 2 pts What ionization source is used in the mass spectrometer in the 425 laboratory Page 6 of 10 B 2 pts Name the two ionization sources that are used most commonly for the analysis of high molecular weight polar compounds such as proteins C 2 pts What mass analyzer is employed in the GC MS in the 425 laboratory D 2 pts For what reason is this mass analyzer employed in the GC MS in the 425 laboratory E 2 pts Name three other mass analyzers Ultraviolet Visible Absorption Spectrophotometry 10 points 6 A 2 pts Name two



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