CHM
M134 Generaal Chemistryy I
Exam
mination 4, Fall
F 2008
Name
1. C
Calculate the heat transfeerred in the following
f
reaaction (ΔHrxnn). Indicate which
direction (exo
othermic or endothermic
e
c) the heat is transferred.. (5 points)
H
H Cl
Cl
+
C C
Cl
F
F
F C C H
H
Cl F
2. A
Assign formaal charges to the elementts in each off the structurees below andd enter the
reesults in the boxes below
w each structture. Based on your assiigned formall charges,
ciircle the stru
ucture that makes
m
the greeatest contribbution to thee correct struucture of
C -. (10 po
CNO
oints)
A
B
C
Formal Charge
C
N
O
3. D
Draw a Lewiss structure foor CH3CN thhat obeys alll octet/duet rules
r
for the atoms.
Innclude reson
nance forms if necessary. (5 points)
4. Draw a Lewis structure for BrO3- that is based on the best possible formal charges.
Include any resonance forms if necessary. (5 points)
5. In the first column, draw a Lewis Dot structure for each species. In the second
column, provide a 3D sketch of the species that includes estimated bond angles and
the name of the shape. The first one is done for you as an example. (24 points)
LEWIS DOT STRUCTURE
VSEPR Sketch
CH4
H
H
109.5 o
H
C
H
C
H
H
H
H
shape name:
tetrahedral
NH3
shape name:________________________________
CO2
shape name:________________________________
SF4
shape name:________________________________
BF3
shape name:________________________________
6. From the list below, circle which molecule(s) are linear. (6 points)
H2O
XeCl2
CS2
SO2
BeCl2
CH4
7. From the list below, circle which molecule(s) are polar (having a non-zero dipole
moment). (6 points)
CH4
H2O
SF4
PCl5
SF6
NCl3
8. Using periodic trends, place the following bonds in order of increasing ionic
character. (2 points)
S-F
Se-F O-F
9. From the list below, circle which molecule(s) contain pure covalent bonds. (6 points)
NaCl
PF3
Cl2
H2O
H2
LiH
10. From the list below, circle which atom(s) can form compounds with expanded octets.
(6 points)
N
Be
S
Br
O
He
11. Consider the molecule below. Determine the hybridization at each of the numbered
carbons. Also, indicate the total number of sigma and pi bonds on the structure,
respectively. (8 points)
C1 _________
C2 _________
sigma bonds
pi bonds
12. A molecule whose center has sp3d2 hybridization falls into which electron pair
geometry family? (2 points)
Answer: ________________________
Use the molecular orbital diagram shown to answer the questions below.
13. What is the bond order of the O22+ ion? (3 points)
14. Circle any species that will be diamagnetic. (5 points)
O22+
O21+
O2
O21-
O22-
15. What is the bond order of the F2 molecule? (3 points)
16. For the series of species below, which has the shortest bond length and which has the
longest? (4 points)
F22+
F21+
F2
F21-