Chapter 9 Flashcards


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Chem 121 Molecular Geometry and Bonding Theories
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1

The basis of the VSEPR model of molecular bonding is __________.
A) regions of electron density on an atom will organize themselves so as to maximize s-character
B) regions of electron density in the valence shell of an atom will arrange themselves so as to maximize
overlap
C) atomic orbitals of the bonding atoms must overlap for a bond to form
D) electron domains in the valence shell of an atom will arrange themselves so as to minimize repulsions
E) hybrid orbitals will form as necessary to, as closely as possible, achieve spherical symmetry

Answer: D

2

According to VSEPR theory, if there are three electron domains in the valence shell of an atom, they
will be arranged in a(n) __________ geometry.
A) octahedral
B) linear
C) tetrahedral
D) trigonal planar
E) trigonal bipyramidal

Answer: D

3

In counting the electron domains around the central atom in VSEPR theory, a __________ is not
included.
A) nonbonding pair of electrons
B) single covalent bond
C) core level electron pair
D) double covalent bond
E) triple covalent bond

Answer: C

4

The electron-domain geometry of __________ is tetrahedral.
A) CBr4
B) PH3
C) CCl2BR2
D) XeF4
E) all of the above except XeF4

Answer: E

5

The O–C–O bond angle in the CO32- ion is approximately __________.
A) 90°
B) 109.5°
C) 120°
D) 180°
E) 60°

Answer: C

6

The Cl–C–Cl bond angle in the CCl O2 molecule (C is the central atom) is slightly __________.
A) greater than 90°
B) less than 109.5°
C) less than 120°
D) greater than 120°
E) greater than 109.5°

Answer: C

7

Of the following species, __________ will have bond angles of 120°.
A) PH3
B) ClF3
C) NCl3
D) BCl3
E) All of these will have bond angles of 120°.

Answer: D

8

An electron domain consists of __________.
a) a nonbonding pair of electrons
b) a single bond
c) a multiple bond

A) a only
B) b only
C) c only
D) a, b, and c
E) b and c

Answer: D

9

According to VSEPR theory, if there are three electron domains on a central atom, they will be
arranged such that the angles between the domains are __________.
A) 90°
B) 180°
C) 109.5°
D) 360°
E) 120°

Answer: E

10

According to VSEPR theory, if there are two electron domains on a central atom, they will be arranged
such that the angles between the domains are __________.
A) 360°
B) 120°
C) 109.5°
D) 180°
E) 90°

Answer: D

11

According to VSEPR theory, if there are four electron domains on a central atom, they will be
arranged such that the angles between the domains are __________.
A) 120°
B) 109.5°
C) 180°
D) 360°
E) 90°

Answer: B

12

The electron-domain geometry and the molecular geometry of a molecule of the general
formula ABn are __________.
A) never the same
B) always the same
C) sometimes the same
D) not related
E) mirror images of one another

Answer: C

13

The electron-domain geometry and the molecular geometry of a molecule of the general
formula ABn will always be the same if __________.
A) there are no lone pairs on the central atom
B) there is more than one central atom
C) n is greater than four
D) n is less than four
E) the octet rule is obeyed

Answer: A

14

For molecules of the general formula ABn , n can be greater than four __________.
A) for any element A
B) only when A is an element from the third period or below the third period
C) only when A is boron or beryllium
D) only when A is carbon
E) only when A is Xe

Answer: B

15

Consider the following species when answering the following questions:
(i) PCl3 (ii) CCl4 (iii) TeCl4 (iv) XeF4 (v) SF6

For which of the molecules is the molecular geometry (shape) the same as the VSEPR electron domain
arrangement (electron domain geometry)?
A) (i) and (ii)
B) (i) and (iii)
C) (ii) and (v)
D) (iv) and (v)
E) (v) only

Answer: C

16

Of the molecules below, only __________ is polar.
A) SbF5
B) AsH3
C) 2I
D) SF6
E) CH4

Answer: B

17

The combination of two atomic orbitals results in the formation of __________ molecular orbitals.
A) 1
B) 2
C) 3
D) 4
E) 0

Answer: B

18

The 3 2 sp d atomic hybrid orbital set accommodates __________ electron domains.
A) 2
B) 3
C) 4
D) 5
E) 6

Answer: E

19

The 2 sp atomic hybrid orbital set accommodates __________ electron domains.
A) 2
B) 3
C) 4
D) 5
E) 6

Answer: B

20

When three atomic orbitals are mixed to form hybrid orbitals, how many hybrid orbitals are formed?
A) one
B) six
C) three
D) four
E) five

Answer: C

21

The blending of one s atomic orbital and two p atomic orbitals produces __________.
A) three sp hybrid orbitals
B) two 2 sp hybrid orbitals
C) three 3 sp hybrid orbitals
D) two 3 sp hybrid orbitals
E) three 2 sp hybrid orbitals

Answer: E

22

A triatomic molecule cannot be linear if the hybridization of the central atoms is __________.
A) sp
B) 2 sp
C) 3 sp
D) 2 sp or 3 sp
E) 2 sp d or 3 2 sp d

Answer: D

23

A typical double bond __________.
A) is stronger and shorter than a single bond
B) consists of one σ bond and one π bond
C) imparts rigidity to a molecule
D) consists of two shared electron pairs
E) All of the above answers are correct.

Answer: E

24

A typical triple bond __________.
A) consists of one σ bond and two π bonds
B) consists of three shared electrons
C) consists of two σ bonds and one π bond
D) consists of six shared electron pairs
E) is longer than a single bond

Answer: A

25

In a polyatomic molecule, "localized" bonding electrons are associated with __________.
A) one particular atom
B) two particular atoms
C) all of the atoms in the molecule
D) all of the π bonds in the molecule
E) two or more σ bonds in the molecule

Answer: B

26

In order to exhibit delocalized π bonding, a molecule must have __________.
A) at least two π bonds
B) at least two resonance structures
C) at least three σ bonds
D) at least four atoms
E) trigonal planar electron domain geometry

Answer: B

27

In a typical multiple bond, the σ bond results from overlap of __________ orbitals and the π bond(s)
result from overlap of __________ orbitals.
A) hybrid, atomic
B) hybrid, hybrid
C) atomic, hybrid
D) hybrid, hybrid or atomic
E) hybrid or atomic, hybrid or atomic

Answer: A

28

The carbon-carbon σ bond in ethylene, CH CH 2 2 , results from the overlap of __________.
A) sp hybrid orbitals
B) 3 sp hybrid orbitals
C) 2 sp hybrid orbitals
D) s atomic orbitals
E) p atomic orbitals

Answer: C

29

The π bond in ethylene, CH CH 2 2 , results from the overlap of __________.
A) 3 sp hybrid orbitals
B) s atomic orbitals
C) sp hybrid orbitals
D) 2 sp hybrid orbitals
E) p atomic orbitals

Answer: E

30

In order for rotation to occur about a double bond, __________.
A) the σ bond must be broken
B) the π bond must be broken
C) the bonding must be delocalized
D) the bonding must be localized
E) the σ and π bonds must both be broken

Answer: B

31

A typical triple bond consists of __________.
A) three sigma bonds
B) three pi bonds
C) one sigma and two pi bonds
D) two sigma and one pi bond
E) three ionic bonds

Answer: C

32

The N–N bond in HNNH consists of __________.
A) one σ bond and one π bond
B) one σ bond and two π bonds
C) two σ bonds and one π bond
D) two σ bonds and two π bonds
E) one σ bond and no π bonds

Answer: A

33

The hybridization of the terminal carbons in the H C=C=CH 2 2 molecule is __________.
A) sp
B) 2 sp
C) 3 sp
D) 3 sp d
E) 3 2 sp d

Answer: B

34

Electrons in __________ bonds remain localized between two atoms. Electrons in __________
bonds can become delocalized between more than two atoms.
A) pi, sigma
B) sigma, pi
C) pi, pi
D) sigma, sigma
E) ionic, sigma

Answer: B

35

The bond order of any molecule containing equal numbers of bonding and antibonding electrons is
__________.
A) 0
B) 1
C) 2
D) 3
E) 1/2

Answer: A

36

An antibonding π orbital contains a maximum of __________ electrons.
A) 1
B) 2
C) 4
D) 6
E) 8

Answer: B

37

According to MO theory, overlap of two s atomic orbitals produces __________.
A) one bonding molecular orbital and one hybrid orbital
B) two bonding molecular orbitals
C) two bonding molecular orbitals and two antibonding molecular orbitals
D) two bonding molecular orbitals and one antibonding molecular orbital
E) one bonding molecular orbital and one antibonding molecular orbital

Answer: E

38

Molecular Orbital theory correctly predicts paramagnetism of oxygen gas, O2 . This is because
__________.
A) the bond order in O2 can be shown to be equal to 2.
B) there are more electrons in the bonding orbitals than in the antibonding orbitals.
C) the energy of the 2p π MOs is higher than that of the σ2pMO
D) there are two unpaired electrons in the MO electron configuration of O2
E) the O–O bond distance is relatively short

Answer: D

39

Molecular Orbital theory correctly predicts diamagnetism of fluorine gas, F2 . This is because
__________.
A) the bond order in F2 can be shown to be equal to 1.
B) there are more electrons in the bonding orbitals than in the antibonding orbitals.
C) all electrons in the MO electron configuration of F2 are paired.
D) the energy of the 2p π MOs is higher than that of the σ2pMO
E) the F–F bond enthalpy is very low

Answer: C