Los Angeles City College Chemistry 60
Bonding Practice Problems with ANSWERS
1.
Consider each of the following ions/molecules shown below and write your final
structures in the boxes provided:
A.
B.
C.
D.
Beginning with the best Lewis dot structure, use VSEPR theory to
draw each of the listed species, including resonance where
appropriate. Don’t forget to include lone pairs!
Describe the geometry about EACH central atom. Include both
electronic and molecular geometries.
Give the approximate bond angle(s) around each central atom.
Determine whether the overall species is polar or nonpolar.
i.
ii.
POCl3
ClO3+
Structure #1
iii.
iv.
SCNSbBr3
Structure #2
electronic geometry:
electronic geometry:
molecular geometry:
molecular geometry:
approx. bond angle:
approx. bond angle:
polar or nonpolar?
polar or nonpolar?
Structure #3
Structure #4
electronic geometry:
electronic geometry:
molecular geometry:
molecular geometry:
approx. bond angle:
approx. bond angle:
polar or nonpolar?
polar or nonpolar?
2.
Use VSEPR theory to draw the two structural isomers for C2H6S. Which isomers
are polar/nonpolar? Make sure to clearly label your structures.
3.
Consider the protein aspartame shown below, a common artificial sweetener
derived from aspartic acid and phenylalanine:
H
C
H
O
H
B.
C.
D.
CH
NH2
CH
C
CH
H2C
C
C
C
O
A.
O
H
HC
C
H
CH
O
N
C
H
O
H
C
H
H
Use an arrow labeled “A” (A →) to identify ONE central atom with a bent
geometry and an approximate bond angle of 109.5º.
Use an arrow labeled “B” (B →) to identify ONE central atom with a
trigonal pyramidal geometry and an approximate bond angle of 109.5º.
Use an arrow labeled “C” (C →) to identify ONE central atom with a
trigonal planar geometry and an approximate bond angle of 120º.
Does this particular protein exhibit resonance? Briefly explain why or
why not.
4.
Consider each of the following ions/molecules shown below and write your final
structures in the boxes provided:
A.
B.
C.
D.
Beginning with the best Lewis dot structure, use VSEPR theory to
draw each of the listed species, including resonance where
appropriate. Don’t forget to include lone pairs!
Describe the geometry about EACH central atom. Include both
electronic and molecular geometries.
Give the approximate bond angle(s) around each central atom.
Determine whether the overall species is polar or nonpolar.
i.
ii.
SOCl2
HCHO
Structure #1
iii.
iv.
OCNHONO2
Structure #2
electronic geometry:
electronic geometry:
molecular geometry:
molecular geometry:
approx. bond angle:
approx. bond angle:
polar or nonpolar?
polar or nonpolar?
Structure #3
Structure #4
electronic geometry:
electronic geometry:
molecular geometry:
molecular geometry:
approx. bond angle:
approx. bond angle:
polar or nonpolar?
polar or nonpolar?
For Questions 5 – 7, reference the structure of Vitamin E below:
H2
C
H
C
HO
C
C
HC
C
CH3
H2
C
CH
O
C
H
5.
CH2
C
H2
CH3
H2
C
CH
C
H2
CH3
H2
C
CH
C
H2
C
H2
C
H2
CH
C
H2
CH3
Based on your knowledge of VSEPR, which of the following geometries is NOT
present in Vitamin E?
A.
B.
C.
D.
E.
trigonal planar
tetrahedral
bent
trigonal pyramidal
All of the above are present in Vitamin E.
6.
Select “A” for True OR “B” for False regarding the following statement:
Vitamin E does not possess any resonance.
7.
Select “A” for True OR “B” for False regarding the following statement:
Vitamin E is a slightly polar molecule although predominantly nonpolar.
8.
Consider the INCOMPLETE Lewis structure for the naphthalene molecule
(C10H8) shown below. All the observed C-C bond lengths in the molecule are
known to be intermediate between C-C single and C=C double bonds. Explain,
making sure to complete the resonance representation shown below.
H
H
H
H
C
C
C
H
C
C
C
H
H
C
C
C
C
H
H
H
H
H
C
C
H
C
C
C
C
C
C
C
C
H
H
H
ANSWERS
1.
Note that terminal atoms are assumed to have an octet of electrons (excluding
hydrogen) – omitted for the sake of clarity!
O
P
Cl
Cl
O
O
O
Cl
Cl
Cl
O
O
O
O
Cl
Structure #1
O
O
Structure #2
electronic geometry: tetrahedral
electronic geometry: trigonal planar
molecular geometry: tetrahedral
molecular geometry: trigonal planar
approx. bond angle: 109.5 degrees
approx. bond angle: 120 degrees
polar or nonpolar? polar
polar or nonpolar? ionic (nonpolar)
S
C
N
S
S
C
C
N
Sb
N
Br
Structure #3
Br
Br
Structure #4
electronic geometry: linear
electronic geometry: tetrahedral
molecular geometry: linear
molecular geometry: trigonal pyramidal
approx. bond angle: 180 degrees
approx. bond angle: 109.5 degrees
polar or nonpolar? polar
polar or nonpolar? polar
2.
Structural isomers are molecules with the same chemical formula but different
connectivity of atoms. Consider the two structures below:
H
H
H
C
C
H
S
H
Polar
H
H
S
H
C
and
H
C
H
H
Polar
H
3.
Consider the protein aspartame shown below, a common artificial sweetener
derived from aspartic acid and phenylalanine:
H
C
all carbons in ring are "C" HC
A
C
CH
O
H
B
B.
C.
D.
H
O
H2C
C
C
C
C
C
O
A.
CH
CH
NH2
CH
CH
A
C
H
O
N
C
H
O
H
C
H
H
B
Use an arrow labeled “A” (A →) to identify ONE central atom with a bent
geometry and an approximate bond angle of 109.5º. see above
Use an arrow labeled “B” (B →) to identify ONE central atom with a
trigonal pyramidal geometry and an approximate bond angle of 109.5º.
see above
Use an arrow labeled “C” (C →) to identify ONE central atom with a
trigonal planar geometry and an approximate bond angle of 120º. see
above
Does this particular protein exhibit resonance? Briefly explain why or
why not. Yes, one example is circled above. Electrons can be
delocalized throughout the protein via single/double bonds.
4.
Note that terminal atoms are assumed to have an octet of electrons (excluding
hydrogen) – omitted for the sake of clarity!
O
S
O
Cl
H
Cl
Structure #1
C
H
Structure #2
electronic geometry: tetrahedral
electronic geometry: trigonal planar
molecular geometry: trigonal pyramidal
molecular geometry: trigonal planar
approx. bond angle: 109.5 degrees
approx. bond angle: 120 degrees
polar or nonpolar? polar
polar or nonpolar? polar
O C N
O C N
H
O
O C N
N
O
Structure #3
O
H
O
N
O
O
Structure #4
electronic geometry: linear
electronic geometry: (O) tetrahedral;
(N) trigonal planar
molecular geometry: (O) bent;
(N) trigonal planar
approx. bond angle: (O) 109.5 degrees;
(N) 120 degrees
polar or nonpolar? polar
molecular geometry: linear
approx. bond angle: 180 degrees
polar or nonpolar? polar
For Questions 5 – 7, reference the structure of Vitamin E below:
C
C
HC
C
C
H
5.
H2
C
H
C
HO
CH3
CH2
H2
C
CH
O
C
H2
CH3
H2
C
CH
C
H2
C
H2
CH3
H2
C
CH
C
H2
C
H2
CH
C
H2
CH3
Based on your knowledge of VSEPR, which of the following geometries is NOT
present in Vitamin E?
A.
B.
trigonal planar
tetrahedral
C.
D.
E.
bent
trigonal pyramidal
All of the above are present in Vitamin E.
6.
Select “A” for True OR “B” for False regarding the following statement:
Vitamin E does not possess any resonance.
7.
Select “A” for True OR “B” for False regarding the following statement:
Vitamin E is a slightly polar molecule although predominantly nonpolar.
8.
Consider the INCOMPLETE Lewis structure for the naphthalene molecule
(C10H8) shown below. All the observed C-C bond lengths in the molecule are
known to be intermediate between C-C single and C=C double bonds. Explain,
making sure to complete the resonance representation shown below.
H
H
H
H
C
C
H
H
H
H
C
C
H
C
C
C
C
C
C
C
C
C
C
C
C
C
C
H
H
H
H
C
C
H
H
H
The resonance structures shown above depict the delocalization of the carbon
double bonds, giving each carbon atom both single/double bond character.
As a result, the observed C-C bond lengths in the molecule are known to be
intermediate between C-C single and C=C double bonds.