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Unformatted text preview: Chemistry 140A
Winter Quarter, 2008
First Midterm Exam, Monday January 28
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100 score Your answers to this exam are to be only your own work. You may use no written
information during this test period other than the five pages of this exam. You may not
use the back of any pages for answers. Up to one week after your exam is returned you
may submit it for regrading if and only if you have made NO marks on the exam except
for a star (*) next to the number(s) of the question(s) you would like regraded.
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1 23 4 5 6 7 8 90 1 23 4 5 6 7 8 90 1. The activation energy difference necessary to produce a rate difference of 1000:1 is:
2.7 kcal/mole 2. The pKa of H2O is:
14 3. Hybridization of a 2s and a two p orbitals results in:
3 sp hybrid orbitals
3 sp2 hybrid orbitals
2 sp hybrid orbitals
3 sp3 hybrid orbitals 4. The electronegativity of N is:
3.5 5. 3.0
4.0 The pKa of H2O is:
14 6. In heptane, all of the carbon atoms have hybridization of:
sp4 7. Draw electron-dot pictures for NH3 and –OH including all lone pairs of electrons.
Place your answers in the boxes below. 8. Using line notation, draw structures for the following compounds in the boxes
provided. 3-ethylheptane 3-isopropylpentane 3,3-diethylpenane Your signature (in ink)______________________________________________ 2 9. Label all carbon atoms in 2,3,3-trimethylpentane as primary, secondary, tertiary, or
quaternary using the symbols: 1˚, 2˚, 3˚, 4˚. Use the structure provided in the box
below 10. Draw the expected potential-energy diagram for the rotation about the C3-C4 bond
in 2-methylpentane. Only relative energy positions are required, you need not and
should not include any energy values. Include the Newman projections of each
staggered conformation. Include a Newman projection of the highest energy eclipsed
conformationPut your answer in the box below.
4 Your signature (in ink)______________________________________________ 3 11. In the structures shown below, draw circles around all methyl groups and rectangles
around all ethyl groups. Do not guess. A wrong answer will remove credit for a
correct one. Your signature (in ink)______________________________________________ 4 12. Draw all possible constitutional isomers of C7H16 (as line notations, no atoms, only
bond lines). Put your answers in the boxes below. But one and only one isomer in
each of the boxes below. If you duplicate an isomer, neither answer will receive
credit. There may be more boxes than you need. A bonus will be award for perfect
answers. Your signature (in ink)______________________________________________ 5 ...
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This note was uploaded on 10/16/2010 for the course CHEM 6B taught by Professor Crowell during the Spring '08 term at UCSD.
- Spring '08