Wightman - Exam 2 key

Wightman - Exam 2 key - Chemistry 241 SECOND EXAM Name '...

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Unformatted text preview: Chemistry 241 SECOND EXAM Name ' Professor Wightman ' October 12, 2009 (please print) 1. 2. 3. - 4. 5. Planck’s constant = 6.63-x 10'34 joule-sec _ _ Speed of light in vacuum = 3.00 X 108 meters/sec 1. (20 pts.) The atomic emission line best suited for analytical determination ofLi by atomic emission spectroscopy is 670.8 nm. a. Calculate the frequency (in Hz) of this radiation. “1:. b. Calculate the energy (in joules) of a single photon at this wavelength. . ' ‘szvr ' " ; . 3.... , {a F 6.? a. { Wu... 3,. __ a 1 W, i 5, p i, m» . “K 3‘ Z -,{x _ _. A I; Z” . _ g; g, . 5::- c. Calculate the wavelength of this radiation after it enters water, a medium with a refractive index ofl.33. ‘ 6* if??? ’"2? m“ u - M- m- p, 2. (10 pts.) Which region or regions of the electromagnetic spectrum are best suited to observe the following transitions g“ for the use of the following devices. a. Core electron transitions . K W b. Rotational transitions ' g Fails. 0. Nuclear transitions gar” F - d.” Vibrational transitions - E - e. Valence electron transitions I f. Tungsten lamp - 7 {AV ‘ a '5 25% h. Charge coupled device (CCD) ‘ i. nuclear magnetic resonance (NMR) j. Thermocouple k. Deuterium arc lamp 3. (10 points) Indicate whether the following statements are true or false: Fluorescence intensity is not proportional to the molar absorptivity. E ' The absorbance spectrum of a molecule generally is found at longer m wavelengths than its fluorescent spectrum. \W Most molecules exhibit phosphorence that is easily measured. I Samples that have an absorbance greater than 2.0 sholfld be diluted The error in an absorbance measurement is maximal if the transmittance W ' is apprOximately 50%. 4. (20 points) A 5.00 mL aliquot of a standard iron '(II) solution, containing 47 ug of iron per liter, was treated with orthophenanthroline to form the iron (ID—orthophanenthroline complex, and finally diluted to exactly 100 mL. The absorbance of the resulting solution was measured in a 1 cm cell and found to be 0.467 at 510 nm. The atomic weight ofiron is 55.8. a. Calculate the percent transmittance of the solution; $3 " m” ’ W 4“”? fig“? °“" ‘= §gtte¢§g b. Calculate the molar absorptivity of the iron (ID—orthOphenanthroline complex. Ln m e .. a a f? n1 4;“ m A “not 9m“ 24' g” i. enigma Liars at} at is) XE {law we 53%} J E .z: t t Eta; aim; 5. (10 points) a. List the processes that must occur to obtain an atomic emission signal. Start 7 with the sample solution and describe the sequential steps that occur as it is added to the flame with a nebulizer. ' M “5 % at?» {a a it} b. List the major advantage of the inductively coupled plasma compared to a flame for atomic spectroscopy. ' I it: ” {fl . ' RA R 1% . 6. (10 points) a. Draw a block diagram of a electrospray interface. Mfi {it}?st b. What is this deiiice used for? Tfié’vetflmefi ID 1353 is... 56??“ "a «m? We a. E (j 3%,, - 7. (10 points) Two of the isotopes of nickel have atomic masses of 579353 and 59.9332 Da. Calculate the minimum resolving power required to distinguish these isotopes. I 8. (10 points). a. Draw a diagram of a molecular fluorescence instrument. Labei each component. ' \geuwe fi‘éeafieéem"? meummw. @mrwrme! - PLEDGE: I have neither given nor received help. on this examination. SIGNATURE: ...
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Wightman - Exam 2 key - Chemistry 241 SECOND EXAM Name '...

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