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Exam 2 (100 points)CEM 434

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1. (10 pts) Show in the form of an energy level diagram what happens when a moleculeabsorbs light and forms an excited state and then releases the energy. Make sure to

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2. (10 pts) Data obtained from a laser-induced fluorescence measurement of derivatizedamino acids are shown below. Determine the mean and standard error of the mean for

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3. (5 pts) Why are lower detection limits in AAS obtained with a graphite tube furnacerather than a flame?

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4. (10 pts) Describe the processes that occur during the introduction of analyte into aflame for AAS. What factors control how many atoms are detected in a flame atomicabsorption measurement?

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5. (10 pts) Show the design of a typical AAS instrument with a flame. Make sure todetail the optical path the light follows including through any wavelength selector.

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6. (5 pts). In an absorption experiment, a 1 ppm (mg/L) analyte solution (FW = 47 g/mol)gave an absorbance of 0.0065.The instrument used had a path length of 1 cm. What isthe molar extinction coefficient?

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7. (10 pts) Sketch the design of a molecular fluorescence spectrometer. Make sure toshow/ the optical path (details) through any wavelength selector.

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9. (10 pts) How does an interferometer work in FTIR and what are th^ advantages ofusing it as opposed to a dispersive instrument?

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11. (5 pts). An IR measurement of a new compound with a pathlength of 0.5 cmrevealed a transparency of 32% at 1650 cm""" (C=0 stretch) If the molar extinctioncoefficient was found to be 550 I_/mol-cm then what is the concentration of the molecule

present?

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12. (10 pts). Raman spectroscopy is a powerful technique that can have manyadvantages over other common analytical techniques, depending on the purpose of theanalysis. Suppose you were tasked with identifying a particular cosmetic molecule onskin. Could this be done with Raman spectroscopy? If so, how? What would be threeadvantages of Raman spectroscopy over FTIR for identifying bonds in a molecule?

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