Midtermexamsolutions1

Midtermexamsolutions1 - Chemistry 124 First Examination...

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Chemistry 124 First Examination Answers September 26, 2008 Congratulations, you did unusually well on the exam. It appears that you have learned something! Average Score = 80.0 1/3 of scores greater than 85; 2/3 greater than 76. 1. (5 min) A former Chem 125 student sent along a screen capture from last Monday’s Season 3 premiere of Heroes . The character Hiro finds a paper in his father’s safe containing chemical formulae, including one related to the structure of the antiviral Tamiflu shown below. Apparently Hiro says, “I knew I should’ve paid more attention in Chemistry class.” To help Hiro out CIRCLE five functional groups in Tamiflu and NAME THEM. 2. (3 min) Draw a pair of plausible resonance structures for a functional group that appears in Tamiflu . You may show only the functional group and use “R”s to denote other stuff. Use a proper arrow(s) to connect the pair. CH CH CH CH 2 C C O NH 2 C O O C 2 H 5 CH C 2 H 5 C 2 H 5 NH C H 3 C O H ether alkene ester Amide ( NOT carbonyl or ketone or amine - because reactivity is different) amine The ester with an adjacent alkene is properly called an α , β -unsaturated ester, but that will come later. R C NHR O R C NHR O R C OR O R C OR O or
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Chem 124 First Hour Exam 9/26/08 Page 2 3. (4 min) DESCRIBE the nodal pattern in this atomic orbital AND CIRCLE its nickname: 1p 2p 3p 4p 5p 6p There are two spherical nodes (shown as circles) and one planar note (shown as a line). Since there are three nodal surfaces, the principal quantum number, n , must be 4. 4. (4 min) HOW did J. J. Thomson propose to modify Coulomb’s Law in 1923, and WHY ? He added a term ( - c/r ) that would change the sign of the electrostatic force for distances shorter than c (a distance on the order of atomic size). He did this to allow the atom to have a minimum-energy structure despite the restrictions of Earnshaw s Theorem for inverse-square forces. [Note that Thomson had ceased advocating his plum-pudding atom in 1909, when an experiment in the lab of his former star student, Ernest Rutherford, showed that the nucleus was miniscule compared to the size of the atom. Incidentally, Rutherford was a great friend of Bertram Boltwood, the Yale professor responsible for building Sterling Chemistry Lab, which explains why, although he was a physicist, he is the youngest member of the chemistry honor roll on the front of the building. Yale had
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Midtermexamsolutions1 - Chemistry 124 First Examination...

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