14C_f10_e02_key

14C_f10_e02_key - Chemistry 14C Fall 2010 Exam 2 Solutions...

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Chemistry 14C Fall 2010 Exam 2 Solutions Page 1 Statistics : High score, average and low score will be posted on the course web site after exam grading is complete. The exam is ready to be picked up when these numbers are posted. A note about exam keys : The answers presented here may be significantly longer than expected from a student taking the exam. An exam key serves not only to reveal what was expected, but to instruct you as well. To see the projected course grade cutoffs, consult the grading scale on the Chem 14C course web page. 1. MS, 1 H-NMR, 13 C-NMR, and MRI. 2. The structure of DNA can be analyzed by x-ray diffraction. Rosalind Franklin did it! The structure of ice can be analyzed by x-ray diffraction. The structure of Coca-Cola cannot be analyzed by x-ray diffraction because it is not crystalline. 3. (a) Formula = C 6 H 8 O; (6 x 12) + (8 x 1) + (1 x 16) = 96 (b) (6 x 1.107%) + (8 x 0.015%) + (1 x 0.037%) = 6.8% (c) No sulfur, chlorine, or bromine; one oxygen atom (0.2%), so 0%. 4. (a) In the mass spectrum of 2,5-dimethylfuran, a peak at m/z = 81 cannot be a molecular ion. m/z 81 < m/z 96 (M) . (b) In the mass spectrum of 2,5-dimethylfuran, a peak at m/z = 81 definitely is a fragment ion. (c) In the mass spectrum of 2,5-dimethylfuran, a peak at m/z = 81 might be the base peak. Cannot determine for sure without knowing the relative abundance of all ions in the mass spectrum. 5. Zone 2 ( sp 2 C–H), Zone 5 (C=C), and Fingerprint (C–C and C–O). 6. There are two acceptable answers: C C C O C C C H H H H H H H H C C C O C C C H H H H H H H H This bond is most likely to give the largest peak because it is the most polar. This bond is most likely to give the largest peak because it is the most plentiful. Beer's Law . 7.
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This note was uploaded on 09/06/2011 for the course CHEM 140A taught by Professor Whiteshell during the Fall '04 term at UCSD.

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14C_f10_e02_key - Chemistry 14C Fall 2010 Exam 2 Solutions...

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