Chemistry 114
First Hour Exam
Name:____________
1. (30 points) Write the (A)Lewis structures, (B) give the electron arrangement,(C) molecular
structure, (D) the bond angles, (E) the hybridization of the central atom, and (F) predict the
polarity of the following compounds. (Total of 5 points/molecule) Also indicate any alternate
resonance structures.
Br3-
POCl3 (O is central)
B. Trigonal bipyramid
C. Linear
D. 180
E. dsp3
F. Nonpolar
B. tetrahedral
C. tetrahedral
D. 109
E. sp3
F. Polar
ClF3
SO2Cl2 (S is central)
F
F Cl F
Other resonance with =O
B. tetrahedral
C. tetrahedral
D. 109
E. sp3
F. Polar
B. trigonal bipyramid
C. T-shaped
D. 90
E. dsp3
F. Polar
NO-
N2O4
Also resonance structures between =O and -O
B. Trigonal planar
C. Trigonal Planar
D. 120
Resonance with NO triple bond
B. Trigonal Planar
C. Linear
D 180 (not really defined with 2
atoms
E. sp2
F. Polar?
E. sp2
F. Nonpolar
1
2. (10 points) Sketch the triple bond of N2 showing the sigma(F) and pi(B) bonds that make up
the triple bond. What is difference between a sigma bond and a pi bond?
Sigma bonds line along a line that connects the two atoms, pi bonds line above and below (or
side-to-side) of this line. Sigma bonds are slightly stronger than pi bonds
3. (10 points) Using the molecular orbital model, write electron configurations for the following
diatomic species, calculate the bond order for each species, and determine which species are
diamagnetic and paramagnetic
F2+
13 e
F2
14 e
F2p*
B2p*
B2p
F2p
F2s*
F2s
¼¿¼¿
¼¿¼¿
¼¿
¼¿
¼¿
F2p*
B2p*
B2p
F2p
F2s*
F2s
F2p*
B2p*
B2p
F2p
F2s*
F2s
¼¿¼
¼¿¼¿
¼¿
¼¿
¼¿
F215 e
¼
¼¿¼¿
¼¿¼¿
¼¿
¼¿
¼¿
BO
(8-6)/2 = 1
(8-5)/2 = 1.5
Most stable
(8-7)/2 = 0.5
Least stable
Diamagnetic
Paramagnetic
Paramagnetic
2
4. (10 points) Name the following organic chemicals:
H2C CH3
H 3C
H3C CH
C
H2
C CH3
C
C CH3
H2
H 2C
CH3
CH3
A 3-methylpentane
B. trans-3,4-dimethyl-3-hexene
O H
Br
Br
H C C CH3
H
C. Propanal
D. 1,2-dibromobenzene
(o- dibromobenzene)
5. (10 points) Draw structures of the following compounds
A. Cyclohexene
B. para-Dichlorobenzene
Cl
Cl
C. Dimethylether
D. Ethylacetate
O
CH3 O CH3
CH3 CH2 O C CH3
3
6. (10 points) What is the difference between an addition reaction and a substitution reaction?
What types of hydrocarbons undergo these reactions?
In an addition reaction a complete chemical entity is added across a double or triple bond
in an alkene or an alkyne:
F
F
+
H
F
H C C H
H
H H
C C
H
F
H
In a substitution reaction a Substitution is made for a H on an alkane or an aromatic
system, usually with the help of a catalyst:
Cl
+
Cl2
+
HCl
FeCl3
7. (10 points) Why is cyclopropane considered an unstable compound?
Cyclopropane would be a ring system with 3 carbons, so the angle between carbons would
o
be 60 . Sp3 hybridized C normally has a bond angle of 109o. The ideal sp3 hybridized orbitals
don’t line up with the atomic geometry, so there is poor overlap betweent he orbitals, and the
bonds are exceptionally weak, making this an unstable compound.
8. (10 points) Give one example of a monomer and its corresponding polymer that is used in
making a commercial plastic.
Many different examples, the simplest is ethylene (monomer) and polyethylene (polymer)
H
H H
H
C C
H
C C
H
H H
N
Polyethylene (polymer)
Ethylene (mononer)
4