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# exam4key - I CH455 Prof J A Holcombe Exam 4 July 1,2009...

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I CH455 Exam 4 Prof. J. A. Holcombe ----/--+-~~~""""____.----- July 1,2009 Name, (Also write your nam er right"hand corner o/the back side o{the last page o/this exam.) 1. If a solution containing an absorbing species transmits 10% of the incident radiation. ... a) what is the absorbance ofthe solution? (5 pts) b) how much light would be transmitted if the concentration were doubled? (5 pts) -~ /I ::: :2.00 r =- /0 :: [P. 0 I trY' I % c) If the solution is blue, it likely absorbs __ light. (0 blue ~ange 0 UV) (5 pts) 2. a) What is the frequency of light (in Hz) whose wavelength is 400 nm (in a vacuum)? (c = 3xI0 8 m/s; h = 6.6x 10- 27 erg-s) (5 pts) 3)t/"r frM / s --V = -~ ~OO XIP-' M b) What is the wavenumber for this wavelength radiation? (5 pts) I , I07 n "l V ~;::-- -: ! "'"'" c.., t&- 3. IfE: = 35,000 L-mor1-cm· 1 for a strongly absorbing charge transfer complex and j6 smallest absorbance that can be detected is 0.002, what is the limit of detection for this species (in M) for this complex using a 1 cm cell? (5 pts) -i'"" ".00'2- _ ~.7/XII? 1 (! . ~/{fl)( J)

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4. Name a light source that would put out a continuum spectra in the visible region. (5 piS) ~tA,. ..1"'\. <r;"-l7"'~~+- II'~~ ~j1 ~h ---z> 5. Electronic excitation of a molecule occurs in what general region of the spectrum? (5 piS) ~; Jf/O· / 6. Would you expect benzene to absorb light in the UV? In the Visible? JustifY your answer. (5 7. IfNH 3 is added to a Cu 2 + solution; a Cu(NH 3 )42+ complex forms and the solution turns blue. [s this an example of ligand field splitting? IBYES DNO (5 piS) 8. Sunlight reflected off of water, glass or another dielectric material will most likely be . .. (check all that apply) (5 p1J)-- 2 '.1 vvt L Glut b/ Ci1Jartially or fully polarized 0#' ~ ; J.
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exam4key - I CH455 Prof J A Holcombe Exam 4 July 1,2009...

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