Download Ch 10 - 11 Practice Problems - KEY The following problems are

Chem 121
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Ch 10 - 11 Practice Problems - KEY
The following problems are intended to provide you with additional practice in preparing for
the exam. Questions come from the textbook, previous quizzes, previous exams, and other
sources. A solutions manual is supplied in a separate document.
1. Sodium nitrite is an ionic compound containing a polyatomic ion. Answer the following
questions relative to nitrite.
a. Give the Lewis structure of nitrite.
b. Give the hybridization of nitrogen. sp2
c. Illustrate the orbital overlaps in nitrite including the number of electrons in each bond. If σ
or π bonds are present clearly show their presence in the structure.
2. For the molecule, CNClH2, select the answer with the correct number of  and  bonds in the
Lewis structure.
Answer:

4

1
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3. Which of the following cannot be a correct Lewis structure given its molecular formula?
HCN
NO
SO3
COCl2
Answer: NO
4. The molecule below is atorvastatin, the active ingredient in Lipitor.
Fill in the answer for the following aspects of atorvastatin’s structure.
The approximate bond angle at a.
109
The hybridization at b.
sp2
The number of hydrogen atoms bonded at c.
0
The hybridization at d.
sp2
The hybridization at e.
sp3
The number of hydrogen atoms bonded at e.
1
The hybridization at f.
sp3
5. For the following pairs of elements in a covalent bond, which picture is correct?
Answer: N-O
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6. You are given an amino acid that is either glycine (HC 2H4NO2) or alanine (HC 3H6NO2), both of
which are monoprotic acids. To determine which compound you have, you dissolve 0.697 g of
the white solid into 25.00 mL of deionized water and titrate that solution with 17.32 mL of
0.5365 M sodium hydroxide. Identify the acid.
7. Draw 3 acceptable Lewis structures that are isomers of C 2NH2Cl.
8. Which of the following orbital overlaps diagrams will give a pi bond?
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A
B
C
D
E
Answer:____D_____
9. For the following compounds, provide the names for the electronic and molecular
geometries and draw the molecular geometry. Is there an overall molecular dipole moment?
Compound
Molecular
geometry name
NH3
Electronic
geometry
name
Tetrahedral
Molecular geometry
drawing
Molecular dipole
moment? (Y/N)
Trigonal
pyramidal
Y
BrF5
octahedral
Square
pyramidal
Y
I3-
Trig bipyr
Linear
N
SO32-
Tetrahedral
Trigonal
pyramidal
Y
NO2
Trigonal
planar
Bent
Y
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10. What are the electronic and molecular geometries of POF 3?
11. Draw the isomers of PH2Cl3.
12. Of NH3, CaCl2, PCl5, K2O which have predominantly ionic bonding?
Answer: CaCl2 and K2O
13. Based on the Lewis structure for thiocyanate (SCN-, shown), what are the formal charges on
the atoms?
Answer:
S
0
C
0
N
-1
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14. The structure of allene, C 3H4, contains two CH2 members. Each CH2 fragment is in one plane
but the two planes are perpendicular to one another. Draw the Lewis structure of allene. Inside
the box below describe why all of its atoms cannot be in the same plane.
15. Place the following in order of increasing bond length: O 2, N2, Br2, BrCl
Answer: N 2 < O2 < BrCl < Br2 This is based on the bond order and the size of the atomic
orbitals being used for bonding.
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16. Draw the Lewis structures, VSEPR shape including molecular geometry name, and
hybridization of the following:
Formula
Lewis structure
VSEPR and molecular
Hybridization at
geometry
central atom
sp3d
ClF2-
ClF3
sp3d
ClO2-
sp3
ClF5
sp3d2
17. Draw the line drawing of H 2NCH2CHCHCHO. Label the hybridization at each central atom.
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18. For the the following compounds, answer the following questions:
CO32-, SiCl4, ICl3, PH3, PF6-, SO2, H2SO4
a. Which of the following utilize expanded valence for their Lewis structures?
b. Which of the following have a non-zero formal charge on one (or more) of the atoms? Which
atom?
c. What is the hybridization for each central atom?
d. Which of the molecules are polar? Draw in the molecular dipole moment into a VSEPR
drawing.
e. Which of the molecules have resonance structures?
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19. For hydrogen azide, HN3, the bond lengths between two of the nitrogens is 113 pm which it
is 124 pm for the other pair of nitrogen atoms. Also, the H-N-N bond angle is 112 °. Draw a
Lewis structure consistent with this data.
20. The bond dissociation energy of ozone (O 3) is 364 kJ/mol. The bond dissociation energy for
O-O is 142 kJ/mol, and for O=O it is 498 kJ/mol. Using Lewis structures, explain these data.
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21. Give the bond angles in the following compounds.
a.
CCl4
109.5°
b.
PF5
angle between axial and equatorial positions = 90°
angle between equatorial positions = 120°
angle between axial positions = 180°
c.
SiF62-
90°
d.
H2 S
104.5°
e
C 2 H2
180°