Experiment_1_Quiz - range would be a symmetric stretching...

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Travis Collins Experiment 1 – Modeling Stretching Modes of Common Organic Molecules with the Quantum Mechanical Harmonic Oscillator (QMHO) Pre-Lab Quiz 1. What condition needs to be satisfied for a vibrational mode to be IR-active? We must be able to see the normal modes which should be accompanied by a change of dipole moment. 2. What are the absorption bands in the 4000 – 1450 cm -1 IR region usually due to? Give two examples of these modes. The absorption bands of IR region 4000-1450 cm -1 are usually due to stretching vibrations of diatomic units. Some examples of vibration types that would be in this
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Unformatted text preview: range would be a symmetric stretching or asymmetric stretching vibration. 3. What is the wavenumber of the stretching vibrational mode of the CO molecule, given that the force constant of the bond is 650 Nm-1 ? Is this mode IR-active? (Note: μ needs to be in kg.) U = m1m2/(m1+m2) = (12.01)(16)/(12.01+16) = (192.16/28.01) = 6.86g = .00686kg V = (k/u)^.5 /(2 pi c) = (650 Nm-1 / .00686kg )^.5 / (2*3.14*2.998e10 cm/s) V= 1.63e-9 N 4. Why should water be avoided when cleaning and handling the KBr windows? We do not want to use water in these windows because the cells are made out of salt....
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This note was uploaded on 03/18/2008 for the course CHEM 457 taught by Professor Milosavljevic,bramain,alexeisliang,min during the Fall '07 term at Penn State.

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