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Unformatted text preview: Name Ch 1b, Problem Set Three Section Side 1 of 6 Due Friday, Jan. 21, 2011 Rec TA at 4 PM in the Drop Box Problems 1 & 4 are designated ( ! ) as “ no collaboration ” problems. You may not work with others, consult upperclassman, or compare final answers. 1. Rotational Spectroscopy, VSEPR & Permanent Dipole Moments (9 points) If a molecule has no permanent dipole moment, then (to first order) it will not exhibit a rotational absorption spectrum. In problem #2 of PS1, you evaluated two diatomic molecules and one linear, polyatomic molecule. Now consider a non-linear, polyatomic molecule that has one central atom and multiple terminal atoms that are all the same type. If that molecule has the proper symmetry, then it has no permanent dipole moment (and no rotational absorption spectrum). For each of the molecules below, use VSEPR to identify the molecular geometry and use that geometry to determine whether or not the molecule has a permanent dipole moment : (a) NH 3 (b) CH 4 (c) IF 5 Present your answers in a table with three columns (molecule; molecular geometry; dipole moment?) and one row for each molecule. You are not required to draw the structure, but you may need to if you’re having difficulties visualizing the molecule. If you draw the structure, you may also want to assign a dipole moment to each bond by drawing a vector from the negative charge to the positive charge (as done in OGC) or from the positive charge to the negative charge (as done in the lecture notes). Just be consistent. You can then find the total moment by taking a vector sum of the bond dipoles....
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This note was uploaded on 03/21/2011 for the course CHEMISTRY 1b taught by Professor Reisman;heath during the Winter '11 term at Caltech.
- Winter '11