AP Chemistry
Chapter 9. Molecular Geometry and Bonding Theories
Chapter 9. Molecular Geometry and Bonding Theories
Sample Exercise 9.1 (p. 347)
Use the VSEPR model to predict the molecular geometries of
a) O3
b)
SnCl3-
Practice Exercise 1 (9.1)
Consider the AB3 molecules and ions: PCl3, SO3, AlCl3, SO32-, and CH3+. How many of these molecules and
ions do you predict to have a trigonal-planar geometry?
a)
1
b) 2
c) 3
d) 4
Practice Exercise 9.1
Predict the electron-domain geometry and the molecular geometry for
a)
SeCl2
b)
CO32-
-1-
e) 5
AP Chemistry
Chapter 9. Molecular Geometry and Bonding Theories
Sample Exercise 9.2 (p. 354)
Use the VSEPR model to predict the molecular geometry of
a) SF4
b)
IF5
Practice Exercise 1 (9.2)
A certain AB4 molecule has a square-planar molecular geometry. Which of the following statements about the
molecule is or are true?
(i) The molecule has four electron domains about the central atom
(ii) The B-A-B angles between neighboring B atoms is 90o.
(iii) The molecule has two nonbonding pairs of electrons on atom A.
a)
b)
c)
d)
e)
Only one of the statements is true.
Statements (i) and (ii) are true.
Statements (i) and (iii) are true.
Statements (ii) and (iii) are true.
All three statements are true.
Practice Exercise 2 (9.2)
Predict the electron-domain geometry and molecular geometry of
a)
BrF5+
b) SF5+
-2-
AP Chemistry
Chapter 9. Molecular Geometry and Bonding Theories
Sample Exercise 9.3 (p. 355)
Eyedrops for dry eyes usually contain a water-soluble polymer called polyvinylalcohol, which is based on the
unstable organic molecule called vinyl alcohol. Predict the approximate values for the H-O-C and O-C-C bond
angles in vinyl alcohol.
Practice Exercise 1 (9.3)
The atoms of the compound methylhydrazine, CH6N2, which is used as a rocket propellant, are connected as
follows (note that lone pairs are not shown): See p. 356 in your textbook.
What do you predict for the ideal values of the C-N-N and H-N-H angles, respectively?
a)
b)
c)
d)
e)
109.5o and 109.5o
109.5o and 120o
120o and 109.5o
120o and 120o
None of the above
Practice Exercise 2 (9.3)
Predict the H—C—H and C—C—C bond angles in the molecule shown, called propyne.
-3-
AP Chemistry
Chapter 9. Molecular Geometry and Bonding Theories
Sample Exercise 9.4 (p. 357)
Predict whether the following molecules are polar or nonpolar:
a)
BrCl
b)
SO2
c)
SF6
Practice Exercise 1 (9.4)
Consider an AB3 molecule in which A and B differ in electronegativity. You are told that the molecule has an
overall dipole moment of zero. Which of the following could be the molecular geometry of the molecule?
a)
b)
c)
d)
e)
Trigonal pyramidal
Trigonal planar
T-shaped
Tetrahedral
More than one of the above
Practice Exercise 2 (9.4)
Determine whether the following molecules are polar or nonpolar:
a)
SF4
b)
SiCl4
-4-
AP Chemistry
Chapter 9. Molecular Geometry and Bonding Theories
Sample Exercise 9.5 (p. 365)
Describe the orbital hybridization around the central atom in NH2-.
Practice Exercise 1 (9.5)
For which of the following molecules or ions does the following description apply? “The bonding can be
explained using a set of sp2 hybrid orbitals on the central atom, with one of the hybrid orbitals holding a
nonbonding pair of electrons.”
a) CO2
b) H2S
c) O3
d) CO32e) more than one of the above
Practice Exercise 2 (9.5)
Predict the electron-domain geometry and the hybridization of the central atom in SO32-.
-5-
AP Chemistry
Chapter 9. Molecular Geometry and Bonding Theories
Sample Exercise 9.6 (p. 368)
Formaldehyde has the Lewis structure
Describe how the bonds in formaldehyde are formed in terms of overlaps of hybridized and unhybridized
orbitals.
Practice Exercise 1 (9.6)
We have just arrived at a bonding description for the formaldehyde molecule. Which of the following
statements about the molecule is or are true?
(i) Two of the electrons in the molecule are used to make the  bond in the molecule.
(ii) Six of the electrons in the molecule are used to make the  bonds in the molecule.
(iii) The C-O bond length in formaldehyde should be shorter than that in methanol, H3COH.
a)
b)
c)
d)
e)
Only one of the statements is true.
Statements (i) and (ii) are true.
Statements (i) and (iii) are true.
Statements (ii) and (iii) are true.
All three statements are true.
Practice Exercise 2 (9.6)
Consider the acetonitrile molecule:
a) Predict the bond angles around each carbon atom
b) Describe the hybridization at each of the carbon atoms
c) Determine the total number  and  bonds in the molecule.
-6-
AP Chemistry
Chapter 9. Molecular Geometry and Bonding Theories
Sample Exercise 9.7 (p. 371)
Describe the localized  bonding in the nitrate ion, NO3-.
Practice Exercise 1 (9.7)
How many electrons are in the  system of the ozone molecule, O3?
a) 2
b) 4
c) 6
d) 14
e) 18
Practice Exercise 2 (9.7)
Which of the following molecules or ions will exhibit delocalized bonding? SO2, SO3, SO32-, H2CO, NH4+?
Sample Integrative Exercise (p. 386)
Elemental sulfur is a yellow solid that consists of S8 molecules. The structure of the S8 molecule is a puckered,
eight-membered ring.
Heating elemental sulfur to high temperatures produces gaseous S2 molecules.:
S8(s)  4 S2(g)
a) With respect to electronic structure, which element in the second row of the periodic table is most
similar to sulfur?
b) Use the VSEPR model to predict the S-S-S bond angles in S8 and the hybridization at S in S8.
d) Use bond enthalpies (Table 8.4) to estimate the enthalpy change for the reaction just described.
Is the reaction exothermic or endothermic?
-7-