CHM 134 General Chemistry I
Chapter 9 Worksheet, Fall 2009 – Dr. Steel
Name
1. Draw a Lewis structure for each of these species.
a.
b.
c.
d.
e.
BrF41AsCl41SCl2
SiO2
CH4
2. Draw all the possible resonance structures (indicated in parentheses) for each of these
molecules.
a.
b.
c.
d.
HCO21NO21OCN1P2S
(2)
(2)
(3)
(3)
3. Identify the formal charges on each element in these structures.
a.
O
Se
b. H
O
C
1+
c.
S
Cl
4. Use formal charges to determine which resonance structure is the one that most
closely resembles the real structure of the molecule indicated:
a.
C
N
b.
Cl
O
-1
C
N
O
-1
C
O
O
O
C
C
C
Br
Cl
Br
Cl
N
O
-1
Br
5. Categorize the bond that forms between the two atoms in each pair below as covalent,
polar covalent, or ionic.
a. I – Cl
d. C – C
b. Na – Cl
e. P – Si
c. H – N
f. Ca – O
6. Estimate the enthalpy change (ΔHrxn)for each reaction below.
a. CH3OH → CO + 2 H2
b. C2H4 + Cl2 → C2H4Cl2
(C2H4 has a double bond, C2H4Cl2 does not)
Answers:
1. a. BrF41-
-1
F
F
Br
b. AsCl5
c. SCl2
Cl
Cl
F
Cl
As
F
S
Cl
Cl
Cl
H
d. SiO2
O
Si
e. CH4
O
C
H
H
H
1-
O
2. a. HCO21- (2)
C
H
1-
O
O
O
C
H
1-
1b. NO21-
(2)
O
c. OCN1-
(3)
O
d. P2S
(3)
3. a. O -1
Se +1
O 0
P
b. H 0
C 0
S 0
Cl 0
N
C
P
N
-1
S
N
O
O
O
C
P
P
O
N
-1
O
S
c. Cl +3
O -1
F 0
4. a. first structure, smallest charges, neg. on O (none of these is favorable, though)
b. first structure, no formal charges on any element
5. a. polar, b. ionic, c. polar, d. covalent, e. covalent, f. ionic
6. a. +122 kJ, b. -171 kJ
C
P
N
P
-1
S