prelab 1 - CHM 318L.03(W08 ORGANIC CHEMISTRY...

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CHM 318L.03 (W08) ORGANIC CHEMISTRY LAB (08W_CSCI_CHM318L.03) > QUIZZES > REVIEW ASSESSMENT: IR QUIZ BB Review Assessment: IR Quiz Bb Submitted 1/15/08 6:53 PM Name IR Quiz Bb Status Completed Score 100 out of 100 points Instructions Question 1 5 out of 5 points The first several questions deal with the nature of infrared light energy. Which of the following regions of the electromagnetic spectrum are arranged in the order of INCREASING energy? Selected Answer: radio < microwave < infrared < visible < UV < X-rays Feedback: The shorter the wavelength, the higher the light energy. X-rays have the shortest wavelength and are highest in energy. Radio waves are very long (on the order of meters) and low energy. Question 2 5 out of 5 points Which of the following are usually measured in reciprocal centimeters (cm -1 )? Selected Answer: wavenumber Feedback: wavenumber = 1/wavelength Question 3 5 out of 5 points As wavenumbers (cm -1 ) INCREASE, energy ______________. Selected Answer: increases Feedback: Energy is directly proportional to wavenumbers. Since the process of bond stretching requires more energy than bond bending (think of a bond as a rubber band or spring), stretching peaks occur at higher wavenumbers. For example, an sp 3 C-H stretch is ~3000-2900 -1 and an sp 3 C-H bend is ~1400 -1 . Question 4 5 out of 5 points If a bond motion (stretching or bending) does not change the dipole moment of the molecule, there will be no peak in the IR spectrum corresponding to that motion.
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Selected Answer: True Feedback: Only those motions that result in a change of the molecule's dipole moment will absorb IR light. Symmetrical molecules, such as H 2 , do not absorb IR radiation (and, therefore, will not appear in an IR spectrum). Question 5 20 out of 20 points The next several questions deal with interpretation of IR spectra.
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