CHM134 General Chemistry I
Exam 3, Fall 2014
Name
1. Draw a reasonable Lewis Dot Structure for each of these species. Show all valence
electrons. None of these require you to violate the octet rule. (12 points)
SCl2
PH3
CO2
N2
2. Draw a reasonable Lewis Dot Structure for each of these species. Show all valence
electrons. Each of these requires you to violate the octet rule. (9 points)
ClF5
PCl5
XeF2
3. Draw a Lewis dot structure for the formaldehyde molecule (CH2O). This molecule has the
carbon at the center and the other three atoms bonded to it. (6 points)
4. Based on the Lewis Structures provided, complete the table below by providing a sketch of
the species (in 3-D, if appropriate), supplying the idealized bond angles, naming the
molecular geometry of the species, identifying the type of orbital hybridization present on the
central atom of the species, and indicating whether the species is polar or nonpolar.
(24 points)
Molecule
Lewis
Structure
Electron pair
geometry
Sketch
(with angles)
VSEPR
Geometry
Hybridization
on central
atom
polar or
non-polar?
BF3
SeBr4
NH3
SF6
5. Assign formal charges to the elements in each of the structures below. Based on your
assigned formal charges, circle the structure that makes the greatest contribution to the
correct structure of the species. (7 points)
H
C
S
6. Use bond energies from the table provided to determine the enthalpy change for the
following reaction. (8 points)
Is this reaction exothermic (heat released) or endothermic (heat consumed)? ________________
7. Consider the structure of vitamin C shown below to answer the following (15 points)
a. How many sigma () bonds are present in the vitamin C structure? ________
b. How many pi () bonds are present in the vitamin C structure? ________
c. How many sp2 hybridized carbon atoms are present in the vitamin C structure? ______
d. How many sp3 hybridized carbon atoms are present in the vitamin C structure? ______
e.
How many sp3 hybridized oxygen atoms are present in the vitamin C structure? _______
8. What type of orbital interaction is shown in the figure? (2 pts.)
9. What type of orbital interaction is shown in the figure? (2 pts.)
Use the following molecular orbital diagram to help answer the remaining questions. (15 pts.)
10. According to molecular orbital theory, what is the bond order in the F2 molecule? ________
11. According to molecular orbital theory, is the F2 molecule paramagnetic? ________
13. According to molecular orbital theory, which species below will not exist in the gas-phase?
F22+
F2
F22-
14. According to molecular orbital theory, which of these species has the greatest bond order?
O22+
O2
O22-
15. According to molecular orbital theory, which of these species is paramagnetic?
O22+
O2
O22-