AP Chemistry - Problem Drill 15: Lewis Structures and VSEPR Theory No. 1 of 10 1. Which shape would have sp 3 hybridization? (A) Linear (B) Bent (C) Tetrahedron (D) Trigonal planar (E) Octahedron C. Correct. E. Incorrect. Linear can be either AX 2 or AX 2 10 3 either 2 or 5 electron regions. Bent can be either AX 2 E or AX 2 10 2 either 2 or 3 electron regions. Tetrahedron is AX 4 4 electron regions. Octahedron is AX 6 6 electron regions. Trigonal planar is AX 3 3 electron regions. The correct answer is (C).
No. 2 of 10 2. Which best describes HCOOH? Unshared electron pairs Shared electron pairs in a single bond A 0 2 2 B 0 1 2 C 1 2 1 D 4 3 2 E 3 2 1 Shared electron pairs in a double bond Draw the Lewis structure for HCOOH and count each type. Draw the Lewis structure for HCOOH and count each type. Draw the Lewis structure for HCOOH and count each type. 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).
No. 3 of 10 3. Which gives the correct comparison of the carbon-carbon bond characteristics between C 2 H 4 and C 2 H 2? Compared to C 2 H 4, the bond characteristics for C 2 H 2 are: Bond length Bond strength Number of shared electron pairs A Greater Smaller Greater B Greater Smaller Smaller C Smaller Smaller Smaller D Smaller Greater Greater E Smaller Smaller Greater C 2 H 4 has single carbon-carbon bonds and C 2 H 2 has double carbon-carbon bonds. C 2 H 4 has single carbon-carbon bonds and C 2 H 2 has double carbon-carbon bonds. C 2 H 4 has single carbon-carbon bonds and C 2 H 2 has double carbon-carbon bonds. D. Correct. C 2 H 4 has single carbon-carbon bonds and C 2 H 2 has double carbon-carbon bonds. C 2 H 4 has single carbon-carbon bonds and C 2 H 2 has double carbon-carbon bonds. Draw the structures for each molecule. Each increase in shared electrons results in stronger and shorter bonds. C 2 H 2 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).
No. 4 of 10 4. Give the VSEPR shape for CO 2-3 : (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. This molecule has 3 bonding regions and no lone pairs. This molecule has 3 bonding regions and no lone pairs. This molecule has 3 bonding regions and no lone pairs. This molecule has 3 bonding regions and no lone pairs. CO 3-2 has three bonding regions and no long pair regions. This is trigonal planar shape. The correct answer is (A).
No. 5 of 10 5. Which has a larger Cl-P-Cl bond angle, PCl 3 or PCl 4 +. (A) PCl 3 (B) PCl 4 + (C) They are both the same. (D) Cannot be determined from the given information. (E) None of the above. PCl 3 has a lone pair while the ion does not. B. Correct. PCl 3 has a lone pair while the ion does not. PCl 3 has a lone pair while the ion does not. PCl 3 has a lone pair while the ion does not. E. Incorrect. There is one correct answer above. They both have 4 electron regions. PCl 3 has 1 lone pair wile PCl 4 + has none. Lone pairs distort bond angles in towards each other. Therefore PCl 4 + has a larger bond angle. The correct answer is (B).
No. 6 of 10 6. What is the electron geometry for H 2 S? (A) Linear (B) Bent (C) Trigonal Planar (D) Tetrahedron (E) Octahedron 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. There are two bonding regions and two lone pair regions that s four electron regions total. There are two bonding regions and two lone pair regions that s four electron regions total. 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).
No. 7 of 10 7. What is the molecular geometry for H 2 S? (A) Linear (B) Bent (C) Trigonal planar (D) Tetrahedron (E) Trigonal Pyramidal There are two bonding regions and two lone pair regions. B. Correct. There are two bonding regions and two lone pair regions. There are two bonding regions and two lone pair regions. There are two bonding regions and two lone pair regions. 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).
No. 8 of 10 8. Which molecular geometry always results in polar molecules? (A) Tetrahedron (B) Trigonal bipyramidal (C) Trigonal pyramidal (D) Octahedron (E) Linear 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, one of them has a lone pair of electrons that always results in a net dipole. C. Correct. Although all of them can produce polar molecules, trigonal pyramidal has a lone pair of electrons that always results in a net dipole. 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, 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).
No. 9 of 10 9. What is the molecular geometry for CO 2? (A) Linear (B) Bent (C) Trigonal pyramidal (D) Tetrahedron (E) Trigonal planar A. Correct. There are two bonding regions and no lone pair regions. There are two bonding regions and no lone pair regions. There are two bonding regions and no lone pair regions. There are two bonding regions and no lone pair regions. 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).
No. 10 of 10 10. What is the molecular geometry for PCl 5? (A) Tetrahedron (B) Trigonal pyramidal (C) Trigonal bipyramidal (D) Octahedron (E) Bent There are 5 bonding regions and no lone pair regions. There are 5 bonding regions and no lone pair regions. C. Correct. There are 5 bonding regions and no lone pair regions. There are 5 bonding regions and no lone pair regions. There are 5 bonding regions and no lone pair regions. PCl 5 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).