Deck 9: Molecular Geometry: Shape Determines Function

Question 1

For the series methane, ammonia, and water, the bond angle increases in the following order: H₂O < NH₃ < CH₄. This trend is due to ________

A) a decreasing effective nuclear charge.
B) a decrease in the number of lone pairs.
C) an increase in atomic radius.
D) an increase in the polarity of the molecules.
E) an increasing effective nuclear charge.

Answer 1

a decrease in the number of lone pairs.

Question 2

Which electron-pair geometry corresponds to a steric number of 2?

A) linear
B) trigonal planar
C) tetrahedral
D) trigonal bipyramidal
E) octahedral

Answer 2

linear

Question 3

Which of the following has the largest bond angle?

A) CF₄
B) NF₃
C) F₂O
D) NF₂^-
E) NH₃

Answer 3

CF₄

Question 4

The tetrahedral bond angle is ________.

A) 90^o
B) 180^o
C) 109^o
D) 120^o
E) 105^o

Question 5

The correct H-N-H bond angle in NH₃ is ________

A) the same as the H-O-H angle in water.
B) exactly 109.5 $\degree$ .
C) greater than 109.5 $\degree$ .
D) less than 109.5°.
E) 120°.

Question 6

Which electron-pair geometry has the lowest electron-electron repulsive forces?

A) linear
B) trigonal planar
C) tetrahedral
D) trigonal bipyramidal
E) octahedral

Question 7

Arrange the interactions between pairs of electrons in order of increasing strength.

A) bonding pair-bonding pair < lone pair-bonding pair < lone pair-lone pair
B) bonding pair-bonding pair < lone pair-lone pair < lone pair-bonding pair
C) lone pair-lone pair < lone pair-bonding pair < bonding pair-bonding pair
D) lone pair-lone pair < bonding pair-bonding pair < lone pair-bonding pair
E) lone pair-bonding pair < bonding pair-bonding pair < lone pair-lone pair

Question 8

Which statement about VSEPR theory is not correct?

A) The molecular shape or geometry is determined by the positions of the atoms in the molecule.
B) In VSEPR theory, the shape or geometry of a molecule is determined by electron-electron repulsion.
C) The steric number of a central atom is the sum of the number of bonds around the atom.
D) The steric number has five values from 2 to 6.
E) The electron-pair geometry is determined by the positions of the bonds and lone pairs in a molecule.

Question 9

Why does the seesaw molecular geometry (ss) have a lower energy than the trigonal pyramidal molecular geometry (tp) in an AB₄ molecule with a trigonal bipyramidal electron-pair geometry?

A) The ss geometry has fewer lone-pair bonding-pair interactions at 90^o.
B) The ss geometry has fewer lone-pair bonding pair interactions at 120^o.
C) The ss geometry has fewer bonding-pair bonding-pair interactions at 120^o.
D) The ss geometry has fewer bonding-pair bonding-pair interactions at 90^o.
E) The ss geometry has fewer lone-pair lone-pair interactions at 90^o.

Question 10

Which one of the statements A-D about electron-pair geometry and molecular geometry is not correct?

A) The electron-pair geometry identifies the relative positions of the bonding regions of electrons and the lone pairs of electrons around a central atom in a molecule.
B) The molecular geometry identifies the relative positions of the atoms around a central atom in a molecule.
C) If there are no lone pairs, then the electron-pair geometry and the molecular geometry are the same.
D) The molecular geometry differs from the electron-pair geometry when the number of atoms around the central atom is smaller than the number of regions of electron density.
E) Statements A-D are all correct.

Question 11

Which statement about VSEPR theory is not correct?

A) VSEPR is an acronym for valence-shell electron-pair repulsion.
B) In VSEPR theory, the shape or geometry of a molecule is determined by electron-electron repulsion.
C) The steric number of a central atom is the sum of the number of bonds and lone pairs around the atom.
D) The steric number has five values from 2 to 6.
E) The molecular shape or geometry always is the same as the electron-pair geometry.

Question 12

In VSEPR theory, molecular geometry is determined by ________

A) electron-proton attractive forces.
B) electron-electron attractive forces.
C) electron-electron repulsive forces.
D) proton-proton repulsive forces.
E) electron-nucleus attractive forces.

Question 13

Which electron-pair geometry corresponds to a steric number of 5?

A) linear
B) trigonal planar
C) tetrahedral
D) trigonal bipyramidal
E) octahedral

Question 14

Which bond angle is the smallest?

A) H-C -H in CH₄
B) H-C -H in C₂H₄
C) H-C -H in H₂CO
D) H-C -C in C₂H₂
E) H-C -O in H₂CO

Question 15

A triatomic molecule with a bond angle close to 120^o could be ________.

A) SO₂
B) N₂O
C) HCN
D) CO₂
E) BeH₂

Question 16

Which statement A-D about VSEPR theory is not correct?

A) The molecular shape or geometry can differ from the electron-pair geometry.
B) In VSEPR theory, the shape or geometry of a molecule is determined by electron-electron repulsion.
C) The steric number of a central atom is the sum of the number of bonds and lone pairs around the atom.
D) The steric number has five values from 2 to 6.
E) Statements A-D are all correct.

Question 17

Which electron-pair geometry corresponds to a steric number of 4?

A) linear
B) trigonal planar
C) tetrahedral
D) trigonal bipyramidal
E) octahedral

Question 18

Which statement about the shape or geometry of a molecule is not correct?

A) Physical properties of a substance are not affected by the shape of the molecules.
B) The shape of a molecule refers to the three-dimensional arrangement of the atoms in space.
C) Solubility of a substance in a solvent is affected by the shape of the molecules.
D) Taste and aroma of a substance are affected by the shape of the molecules.
E) Biological activity and chemical reactivity of a substance are affected by the shape of the molecules.

Question 19

Which electron-pair geometry corresponds to a steric number of 3?

A) linear
B) trigonal planar
C) tetrahedral
D) trigonal bipyramidal
E) octahedral

Question 20

Which electron-pair geometry corresponds to a steric number of 6?

A) linear
B) trigonal planar
C) tetrahedral
D) trigonal bipyramidal
E) octahedral

Question 21

All homonuclear diatomic molecules ________

A) have polar bonds.
B) are polar.
C) are nonpolar.
D) cannot vibrate.
E) are liquids.

Question 22

Which of the following is a planar molecule?

A) NH₃
B) PCl₅
C) KrF₄
D) CH₃COOH
E) SiH₄

Question 23

What is the molecular geometry of SF₄O?

A) pentagonal
B) tetrahedral
C) trigonal bipyramidal
D) trigonal planar
E) square pyramidal

Question 24

Which of the following molecules or ions has a trigonal pyramid shape?

A) KrF₄
B) COCl₂
C) SeO₃^2-
D) NH₄⁺
E) O₃

Question 25

Which of the following compounds has the same geometry as SO₂?

A) H₂O
B) HCN
C) ICl₃
D) OCS
E) CO₂

Question 26

Which of the following molecules or ions has a linear molecular geometry?

A) H₂O
B) H₂S
C) ICl₃
D) I₃^-
E) SO₂

Question 27

What is the geometry of the ClF₄^- ion?

A) square planar
B) square pyramidal
C) trigonal pyramidal
D) tetrahedral
E) seesaw

Question 28

What is the molecular geometry of the triiodide ion (I₃^-)?

A) linear
B) bent
C) tetrahedral
D) trigonal pyramidal
E) trigonal planar

Question 29

What is the molecular geometry of SF₄?

A) tetrahedral
B) square pyramidal
C) seesaw
D) square planar
E) T-shaped

Question 30

Which of the following molecules is T-shaped?

A) NCl₃
B) PCl₃
C) SbCl₃
D) ICl₃
E) COCl₂

Question 31

The bond angle in a trigonal planar structure is ________.

A) 90^o
B) 180^o
C) 109^o
D) 120^o
E) 105^o

Question 32

Which bond is the most polar?

A) carbon-oxygen
B) carbon-sulfur
C) carbon-nitrogen
D) carbon-hydrogen
E) carbon-bromine

Question 33

Which bond is the most polar?

A) H-C
B) H-N
C) H-O
D) H-Cl
E) H-F

Question 34

Which bond is the most polar?

A) carbon-oxygen
B) carbon-sulfur
C) carbon-nitrogen
D) carbon-hydrogen
E) carbon-chlorine

Question 35

Determine the molecular geometry of CF₂Cl₂.

A) linear
B) bent
C) trigonal bipyramidal
D) tetrahedral
E) trigonal pyramidal

Question 36

Which of the following compounds has the same molecular shape as CCl₃H?

A) SiF₄
B) KrF₄
C) SF₄
D) C₂H₄
E) C₂H₂

Question 37

Which of the following compounds has a trigonal bipyramidal shape?

A) ICl₃
B) BrF₅
C) PCl₅
D) PH₃
E) SiF₄

Question 38

Which of the following compounds has a square pyramid geometry?

A) ICl₃
B) BrF₅
C) PCl₅
D) PH₃
E) SiF₄

Question 39

Which of the following ions is linear?

A) SCN^-
B) NO₂^-
C) SO₃^2-
D) NH₄⁺
E) SO₂^2-

Question 40

Which of the following molecules or ions is not polar?

A) O₃
B) H₂O
C) SO₂
D) I₃^-
E) S₃

Question 41

What is the hybridization of the oxygen in the H₃O⁺ ion?

A) sp²
B) sp³
C) sp³d
D) sp
E) sp³d²

Question 42

Which of these molecules have a dipole moment?

A) PCl₅ and SiCl₄
B) POCl₃, SO₂Cl₂, and SO₃
C) POCl₃ and SO₂Cl₂
D) PCl₅, POCl₃, SOCl₂, SO₃, and SiCl₄
E) PCl₅, SF₆, SO₃, and SiCl₄

Question 43

Which of the following compounds has the smallest dipole moment?

A) CF₂Cl₂
B) CF₃Cl
C) CF₄
D) CFCl₃
E) CHFCl₂

Question 44

Which of the following statements about bonds between two carbon atoms is/are correct?
(I) Bond strength increases as more electrons are shared between the atoms.
(II) Bond strength increases as the overlap between atomic orbitals increases.
(III) Hybrid orbitals are used to describe (account for) the geometry (bond angles) around each carbon atom.

A) I
B) II
C) III
D) Only two of these are correct statements.
E) All three are correct statements.

Question 45

Which of the following has a central atom with the same hybridization as the oxygen in water?

A) SO₂
B) OCS
C) CS₂
D) NH₃
E) CO₂

Question 46

Which of the following has a central atom with the same hybridization as the carbon in formaldehyde (CH₂O)?

A) SO₂
B) OCS
C) ICl₃
D) I₃^-
E) C₂H₂

Question 47

What is the hybridization of the bromine atom in BrF₅?

A) sp³
B) sp³d
C) sp³d²
D) sp
E) sp²

Question 48

What are the hybridizations of the carbon atoms in CH₃CH₂(CO)H, in order from left to right? Note that the bond is a double bond.

A) sp³, sp³, sp²
B) sp³, sp³, sp³
C) sp³, sp², sp³
D) sp², sp², sp³
E) sp³, sp², sp²

Question 49

Which of the following shows the orientation of the net dipole for OCS?

A)
B)
C)
D)

Question 50

Which of the following compounds has the largest dipole moment?

A) CH₂Cl₂
B) CH₃Cl
C) CHCl₃
D) CCl₄
E) CH₄

Question 51

Which of the following molecules has a central atom that is sp³ hybridized?

A) C₂H₂
B) H₂CO
C) H₂S
D) C₂H₄
E) C₂H₂Cl₂

Question 52

Benzene (C₆H₆) is a cyclic, nonpolar molecule. By removing one of the hydrogens and replacing it with another atom or group, this substituted benzene becomes polar. Which of the following substituted benzenes is the most polar?

A) C₆H₅F (fluorobenzene)
B) C₆H₅Br (bromobenzene)
C) C₆H₅Cl (chlorobenzene)
D) C₆H₅I (iodobenzene)
E) C₆H₅CH₃ (methylbenzene)

Question 53

What hybridization is needed to describe the square planar molecular geometry of KrF₄?

A) sp³
B) sp³d
C) sp³d²
D) sp²
E) sp

Question 54

What is the hybridization of the central iodine atom in I₃^-?

A) sp
B) sp²
C) sp³d
D) sp³d²
E) sp³

Question 55

Identify the polar molecule.

A) CF₄
B) SiH₄
C) CHCl₃
D) CS₂
E) CO₂

Question 56

Which of the following compounds is the most polar?

A) NH₃
B) PH₃
C) AsH₃
D) SbH₃
E) BiH₃

Question 57

Which statement A-D about valence bond theory is not correct?

A) Valence bond theory describes a bond as the overlap of atomic orbitals between two atoms.
B) Enhanced electron density between two positively charged nuclei attracts the nuclei together and forms the bond.
C) Hybridization of atomic orbitals is necessary to account for the molecular geometry.
D) In valence bond theory, hybridization determines the molecular shape or geometry.
E) Statements A-D are all correct.

Question 58

Which of the following diagrams shows the correct orientation of the dipole in sulfur dioxide?

A)
B)
C)
D)

Question 59

Which of the following molecules has a carbon atom that is sp³ hybridized?

A) C₂H₂
B) H₂CO
C) CH₃Cl
D) C₂H₄
E) C₂H₂Cl₂

Question 60

Which statement concerning benzene is not correct?

A) A second resonance structure is needed to describe benzene.
B) All the $\pi$ bonds originate from p atomic orbitals.
C) Benzene does not have a dipole moment.
D) The carbon atomic orbitals are sp² hybridized.
E) Benzene has both long and short carbon-carbon bonds.

Question 61

Which of the following has a local molecular geometry about a carbon atom that is trigonal planar?

A) CH₃CH₂OH
B) CH₃OH
C) C₂H₄
D) CH₃OCH₃
E) C₂H₂

Question 62

Which statement about sigma ( $\sigma$ ) and pi ( $\pi$ ) bonds is not correct?

A) A sigma bond has the region of high electron density aligned along the bond axis, which is the line connecting the two atoms.
B) A pi bond has regions of high electron density lying above and below the bond axis, which is the line connecting the two atoms.
C) A pi bond commonly is formed from the overlap of two unhybridized atomic 2p orbitals.
D) In the trigonal planar geometry, the sigma bonds are formed from the overlap of an sp² hybridized orbital with another orbital.
E) The molecule acetylene, C₂H₂, has five sigma bonds and one pi bond.

Question 63

What type of hybridization is needed to describe the bonding in a T-shaped molecule?

A) sp²
B) sp³
C) sp³d
D) sp
E) sp³d²

Question 64

Which statement about sigma and pi bonds is correct?

A) A pi bond is twice as strong as a sigma bond.
B) A pi bond has cylindrical symmetry about the internuclear axis.
C) A double bond, as in ethylene, consists of a pi bond and a sigma bond.
D) A pi bond, as in ethylene, is described by the overlap of hybridized atomic orbitals.
E) Hydrogen forms pi bonds when it bonds to other atoms.

Question 65

Which statement regarding a pi bond between two carbon atoms is correct?

A) The region of high electron density lies along the bond axis connecting the nuclei of the two atoms.
B) The bond can be described by the overlap of sp hybrid orbitals from each atom.
C) The bond can be described by the overlap of sp² hybrid orbitals from each atom.
D) The bond can be described by the overlap of p atomic orbitals from each atom.
E) The bond can be described by the overlap of a p atomic orbital from one atom with an sp² hybrid orbital from the other atom.

Question 66

The local molecular geometry around carbon atom 2 (second from the left) and its hybridization are ________

A) trigonal bipyramid and sp.
B) trigonal planar and sp³.
C) trigonal planar and sp².
D) tetrahedral and sp³.
E) linear and sp.

Question 67

Ethanol has the formula CH₃CH₂OH. The end carbon atom has a ________ local molecular geometry and ________ hybridization.

A) trigonal planar; sp
B) tetrahedral; sp³
C) tetrahedral; sp²
D) seesaw; sp²
E) seesaw; sp³

Question 68

Which statement regarding a sigma bond between two carbon atoms is not correct?

A) The region of electron density lies along the bond axis connecting the nuclei of the two atoms.
B) The bond can be described by the overlap of sp hybrid orbitals from each atom.
C) The bond can be described by the overlap of sp² hybrid orbitals from each atom.
D) The bond can be described by the overlap of sp³d hybrid orbitals from each atom.
E) The bond can be described by the overlap of an sp² hybrid orbital from one atom with an sp³ hybrid orbital from the other atom.

Question 69

What is the hybridization of the iodine atom in ICl₃?

A) sp²
B) sp³d²
C) sp³d
D) sp³
E) sp

Question 70

Which statement A-D about sigma ( $\sigma$ ) and pi ( $\pi$ ) bonds is not correct?

A) A sigma bond has the region of high electron density aligned along the bond axis, which is the line connecting the two atoms.
B) A pi bond has regions of high electron density lying above and below the bond axis, which is the line connecting the two atoms.
C) A pi bond commonly is formed from the overlap of two unhybridized atomic 2p orbitals.
D) In the trigonal planar geometry, the sigma bonds are formed from the overlap of an sp² hybridized orbital with another orbital.
E) Statements A-D are all correct.

Question 71

Ethanol has the formula CH₃CH₂OH. The oxygen atom has a ________ local molecular geometry and ________ hybridization.

A) trigonal planar; sp
B) tetrahedral; sp³
C) tetrahedral; sp²
D) seesaw; sp²
E) bent; sp³

Question 72

What type of hybridization is needed to describe the bonding in a seesaw-shaped molecule?

A) sp²
B) sp³
C) sp³d
D) sp
E) sp³d²

Question 73

Both diazene (N₂H₂) and hydrazine (N₂H₄) have two nitrogen atoms bonded together. In a valence bond picture of the N-N bonds, ________ hybrid orbitals overlap for diazene and ________ hybrid orbitals overlap for hydrazine.

A) sp; sp
B) sp; sp²
C) sp²; sp³
D) sp³; sp²
E) sp²; sp

Question 74

Both ethane (C₂H₆) and ethylene (C₂H₄) have two carbon atoms. In a valence bond picture of the C-C bonds, ________ hybrid orbitals overlap for ethane and ________ hybrid orbitals overlap for ethylene.

A) sp; sp
B) sp; sp²
C) sp²; sp³
D) sp³; sp²
E) sp²; sp

Question 75

Which statement regarding a pi bond between two carbon atoms is correct?

A) Regions of high electron density lie above and below the bond axis connecting the nuclei of the two atoms.
B) The bond can be described by the overlap of sp hybrid orbitals from each atom.
C) The bond can be described by the overlap of sp² hybrid orbitals from each atom.
D) The bond can be described by the overlap of sp³ hybrid orbitals from each atom.
E) The bond can be described by the overlap of a p atomic orbital from one atom with an sp² hybrid orbital from the other atom.

Question 76

Ethanol has the formula CH₃CH₂OH. The central carbon atom has a ________ local molecular geometry and ________ hybridization.

A) trigonal planar; sp
B) tetrahedral; sp³
C) tetrahedral; sp²
D) seesaw; sp²
E) seesaw; sp³

Question 77

For the molecule CH₃CHCHCH₃, the local molecular geometry around a carbon atom at the end and its hybridization are ________

A) trigonal bipyramid and sp.
B) trigonal planar and sp³.
C) trigonal planar and sp².
D) tetrahedral and sp³.
E) linear and sp.

Question 78

Which of the following molecules or ions has a central atom with the same hybridization as PCl₅?

A) IF₆⁺
B) SiF₄
C) BrF₅
D) SbF₅
E) XeF₄

Question 79

The local molecular geometry and the hybridization around each carbon atom in benzene
(C₆H₆ with a hexagonal ring structure) is ________

A) square planar and sp.
B) trigonal planar and sp.
C) tetrahedral and sp³.
D) trigonal planar and sp².
E) T-shaped and sp².

Question 80

Both cyclohexane (C₆H₁₂) and benzene (C₆H₆) have the carbon atoms forming a six-member ring. In a valence bond picture of the C-C bonds, ________ hybrid orbitals would overlap for cyclohexane, and ________ hybrid orbitals would overlap for benzene.

A) sp; sp
B) sp; sp²
C) sp²; sp³
D) sp³; sp²
E) sp³; sp