CHM 374 Spring 2010 HOMEWORK SET 10 Due Wed. April 21 Read Understanding Physical Chemistry ( UPC ), Chapter 8, Section 8.5 1. One can imagine that three hydrogen atoms might combine to form various triatomic molecules or ions (with different geometries and/or different numbers of electrons). a. Use the experimental bond formation energy of H 2 + , U = E B ~ -210 kJ/mol (as given in problem 1 of homework set #9) to determine the Huckel parameter. b. Expand the cyclic trimer secular determinant given in Eq. 8.27 and verify that the resulting polynomial is equivalent to that obtained using the roots given in Eq. 8.28. c. Use the Huckel expressions for energy levels of linear and cyclic triatomics to predict whether the linear or cyclic forms of H 3 + should be the most stable, and compare its predicted bond formation energy with the value of -903 kJ/mol obtained from a very high-level theoretical calculation. d. The relative energy of H
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