College Chemistry - Problem Drill 16: Lewis Structures
Question No. 1 of 10
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needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
1. Which shape would have sp3 hybridization?
Question
(A) Linear
(B) Bent
(C) Tetrahedron
(D) Trigonal planar
(E) Octahedron
A. Incorrect.
sp3 has 4 electron regions.
B. Incorrect.
sp3 has 4 electron regions.
C. Correct.
sp3 has 4 electron regions.
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D. Incorrect.
sp3 has 4 electron regions.
E. Incorrect.
sp3 has 4 electron regions.
sp3 has 4 electron regions.
Linear can be either AX2 or AX2 × 103—either 2 or 5 electron regions.
Bent can be either AX2E or AX2 × 102—either 2 or 3 electron regions.
Tetrahedron is AX4—4 electron regions.
Octahedron is AX6—6 electron regions.
Trigonal planar is AX3—3 electron regions.
The correct answer is (C).
Solution
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Question No. 2 of 10
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needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
2. Which best describes HCOOH?
Unshared
electron pairs
Question
A
B
C
D
E
0
0
1
4
3
Shared
electron pairs
in a single
bond
2
1
2
3
2
Shared
electron pairs
in a double
bond
2
2
1
2
1
A. Incorrect.
Draw the Lewis structure for HCOOH and count each type.
B. Incorrect.
Draw the Lewis structure for HCOOH and count each type.
C. Incorrect.
Draw the Lewis structure for HCOOH and count each type.
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D. Correct.
According to the correct Lewis structure, there are 3 bonded pairs in single bonds,
2 bonded pairs in a double bond and 4 unshared electron pairs.
E. Incorrect.
Draw the Lewis structure for HCOOH and count each type.
Draw the Lewis structure for HCOOH.
HCOOH is a carboxylic acid with a hydrogen on the other side of the carbon in the
carboxylic acid.
There are 3 bonded pairs in single bonds, 2 bonded pairs in a double bond and 4
unshared electron pairs.
The correct answer is (D).
Solution
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Question No. 3 of 10
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needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
3. Which gives the correct comparison of the carbon-carbon bond characteristics
between C2H4 and C2H2? Compared to C2H4, the bond characteristics for C2H2 are:
Question
A
B
C
D
E
Bond length
Bond strength
Greater
Greater
Smaller
Smaller
Smaller
Smaller
Smaller
Smaller
Greater
Smaller
Number of
shared electron
pairs
Greater
Smaller
Smaller
Greater
Greater
A. Incorrect.
C2H4 has single carbon-carbon bonds and C2H2 has double carbon-carbon bonds.
B. Incorrect.
C2H4 has single carbon-carbon bonds and C2H2 has double carbon-carbon bonds.
C. Incorrect.
C2H4 has single carbon-carbon bonds and C2H2 has double carbon-carbon bonds.
Feedback
D. Correct.
C2H4 has single carbon-carbon bonds and C2H2 has double carbon-carbon bonds.
E. Incorrect!
C2H4 has single carbon-carbon bonds and C2H2 has double carbon-carbon bonds.
Draw the structures for each molecule. Each increase in shared electrons results in
stronger and shorter bonds.
Solution
C2H2 has a triple C-C bond. Therefore, it has a smaller bond length, a higher bond
strength and a greater number of shared electrons.
The correct answer is (D).
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Question No. 4 of 10
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needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
4. Give the VSEPR shape for CO32-:
Question
(A) Trigonal planar
(B) Trigonal pyramidal
(C) Tetrahedron
(D) Bent
(E) Linear
A. Correct.
Three bonding regions and no lone pairs is trigonal planar geometry.
B. Incorrect.
This molecule has 3 bonding regions and no lone pairs.
C. Incorrect.
This molecule has 3 bonding regions and no lone pairs.
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D. Incorrect.
This molecule has 3 bonding regions and no lone pairs.
E. Incorrect!
This molecule has 3 bonding regions and no lone pairs.
CO3-2 has three bonding regions and no long pair regions. This is trigonal planar
shape.
The correct answer is (A).
Solution
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Question No. 5 of 10
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needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
5. Which has a larger Cl-P-Cl bond angle, PCl3 or PCl4+.
Question
(A) PCl3
(B) PCl4+
(C) They are both the same.
(D) Cannot be determined from the given information.
(E) None of the above.
A. Incorrect.
PCl3 has a lone pair while the ion does not.
B. Correct.
PCl3 has a lone pair while the ion does not.
C. Incorrect.
Feedback
PCl3 has a lone pair while the ion does not.
D. Incorrect.
PCl3 has a lone pair while the ion does not.
E. Incorrect.
There is one correct answer above.
They both have 4 electron regions. PCl3 has 1 lone pair wile PCl4+ has none. Lone
pairs distort bond angles in towards each other. Therefore PCl4+ has a larger bond
angle.
The correct answer is (B).
Solution
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Question No. 6 of 10
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needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
6. What is the “electron” geometry for H2S?
Question
(A)
(B)
(C)
(D)
(E)
Linear
Bent
Trigonal Planar
Tetrahedron
Octahedron
A. Incorrect.
There are two bonding regions and two lone pair regions—that’s four electron
regions total.
B. Correct.
There are two bonding regions and two lone pair regions—that’s four electron
regions total.
C. Incorrect.
There are two bonding regions and two lone pair regions—that’s four electron
regions total.
Feedback
D. Incorrect.
There are two bonding regions and two lone pair regions—that’s four electron
regions total.
E. Incorrect!
There are two bonding regions and two lone pair regions—that’s four electron
regions total.
Each bond and lone pair count as 1.
4 electron regions
Recognize that although drawn in the plane of the page, lone pair electrons can
exist above or below the plane of the page.
The correct answer is (B).
Solution
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Question No. 7 of 10
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needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
7. What is the “molecular” geometry for H2S?
Question
(A) Linear
(B) Bent
(C) Trigonal planar
(D) Tetrahedron
(E) Trigonal Pyramidal
A. Incorrect.
There are two bonding regions and two lone pair regions.
B. Correct.
There are two bonding regions and two lone pair regions.
C. Incorrect.
There are two bonding regions and two lone pair regions.
Feedback
D. Incorrect.
There are two bonding regions and two lone pair regions.
E. Incorrect!
There are two bonding regions and two lone pair regions.
2 lone pairs, 2 ligands
Recognize that although drawn in the plane of the page, lone pair electrons can
exist above or below the plane of the page.
The correct answer is (B).
Solution
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Question No. 8 of 10
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needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
8. Which molecular geometry always results in polar molecules?
Question
(A) Tetrahedron
(B) Trigonal bipyramidal
(C) Trigonal pyramidal
(D) Octahedron
(E) Linear
A. Incorrect.
Although all of them can produce polar molecules, one of them has a lone pair of
electrons that always results in a net dipole.
B. Incorrect.
Although all of them can produce polar molecules, one of them has a lone pair of
electrons that always results in a net dipole.
C. Correct.
Feedback
Although all of them can produce polar molecules, trigonal pyramidal has a lone
pair of electrons that always results in a net dipole.
D. Incorrect.
Although all of them can produce polar molecules, one of them has a lone pair of
electrons that always results in a net dipole.
E. Incorrect!
Although all of them can produce polar molecules, one of them has a lone pair of
electrons that always results in a net dipole.
Although all of them can produce polar molecules, trigonal pyramidal has a lone
pair of electrons that always results in a net dipole.
The correct answer is (C).
Solution
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Question No. 9 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
9. What is the molecular geometry for CO2?
Question
(A) Linear
(B) Bent
(C) Trigonal pyramidal
(D) Tetrahedron
(E) Trigonal planar
A. Correct.
There are two bonding regions and no lone pair regions.
B. Incorrect.
There are two bonding regions and no lone pair regions.
C. Incorrect.
There are two bonding regions and no lone pair regions.
Feedback
D. Incorrect.
There are two bonding regions and no lone pair regions.
E. Incorrect!
There are two bonding regions and no lone pair regions.
Carbon dioxide is a central carbon with 2 bonding regions to the oxygen atoms—
each is a double bond. Double bonds count the same as singles for VSEPR theory.
So it has 2 bonding regions and no lone pair regions.
The correct answer is (A).
Solution
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Question No. 10 of 10
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needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
10. What is the molecular geometry for PCl5?
Question
(A) Tetrahedron
(B) Trigonal pyramidal
(C) Trigonal bipyramidal
(D) Octahedron
(E) Bent
A. Incorrect.
There are 5 bonding regions and no lone pair regions.
B. Incorrect.
There are 5 bonding regions and no lone pair regions.
C. Correct.
There are 5 bonding regions and no lone pair regions.
Feedback
D. Incorrect.
There are 5 bonding regions and no lone pair regions.
E. Incorrect!
There are 5 bonding regions and no lone pair regions.
PCl5 has 5 bonding regions and no lone pair regions. According to the VSEPR rules,
it is a trigonal bipyramidal geometry.
The correct answer is (C).
Solution
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