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1) linear or bent
2) XeF4
3) trieonal PYramidal
4) linear
5) trigonal PYramidal
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15)
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20) B
21) B
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23) B
24)C
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CHEMISTRY
SCORING GUIDETINES
AP@
2O1O
Ouestion 5
(8 points)
Use the information in the table below to respond to the statements and questions that follow. Your answers
should be in terms of principles of molecular structure and intermolecular forces.
Formula
Lewis Electron-Dot Diagram
Ethanethiol
cH3cH2sH
rt:C:e : S:H
Ethane
cH3cH3
H:C:C:H
Compound
HH
HH
HH
HH
HH
Ethanol
cH3cH2oH
Ethyne
czHz
n:C:C:
HH
H;C
O: H
iiC:H
or
H_C =C_H
(a) Draw the complete Lewis electron-dot diagram for ethyne in the appropriate cell in the table above.
See the lower
right cell in the table above.
One point is earned for the correct Lewis structure'
(b)Which of the four molecules contains the shortest carbon-to-carbon bond? Explain.
Ethyne, which contains a triple bond, has the shortest
C-to-C bond. The other molecules have single C-to-C
bonds, and triple bonds are shorter than single bonds.
One point is eamed for the correct choice'
One point is earned for the correct
explanation.
O 2010 The College Board.
Visit the College Board on the Web: www.collegeboard.com
AP@ CHEI\4ISTRY
2O1O
SCORING GUIDELINES
Ouestion 5 (continued)
(c) A Lewis
electron-dot diagram of a molecule of ethanoic acid is given below. The carbon atoms in the
x and y, respectively.
molecule are labeled
rQ', H
fl:e:er:Cr:fl
H
Identify the geometry of the arrangement of atoms bonded to each of the following.
(i)
Carbon.r
Trigonal planar
(ii)
Carbon
One point is earned for the correct geometry.
y
Distorted tetrahedral, tetrahedral or trigonal pyramidal
I
One point is eamed for the conect geometry.
(d) Energy is required to boil ethanol. Consider the statement "As ethanol boils, energy goes into breaking
C-C bonds, C-H bonds, C*O bonds, and O-H bonds." Is the statement true or false? Justify your
answer.
The statement is false. All of the bonds described are
intramolecular; these bonds are not broken
vaporization. When ethanol boils, the added
overcomes intermolecular, not intramolecular, forces.
during I
energy I
(e) Identiff
One point is eamed for the correct choice with
justification.
a compound from the table above that is nonpolar. Justify your answer.
Either ethane or ethyne may be identified as nonpolar.
The ethane/ethyne molecule is nonpolar because all
of
the bond dipoles in the molecule cancel.
OR
The ethane/ethyne molecule is nonpolar because
molecule is
symmetric.
is earned for a correct choice
the I oi: point
justification'
I with
Note: Explanation must refer to the shape of the
molecule. Statements such as: "all hydrocarbons are
nonpolar', 'the carbons are surrounded by hydrogens"
or "there are no lone pairs" do not earn this point.
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CHEMISTRY
2AIO SCORING GUIDELINES
AP@
Ouestion 5 (continued)
(f)
Ethanol is completely soluble in water, whereas ethanethiol has limited solubility in water' Account for
the difference in solubilities between the two compounds in terms of intermolecular forces.
Ethanol is able to form strong hydrogen bonds with
water whereas ethanethiol does not have similar
capability. The formation of hydrogen bonds increases
the attraction between molecules of ethanol and
molecules of water, making them more soluble in
each other.
One point is earned for the correct explanation.
Note: The answer must clearly focus on the solutesolvent interaction. Just the mention of hydrogen
bonding does not earn the point.
@ 2010
The College Board.
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1) For a molecule with the formula AB2 the molecular shape is
2) The molecular geometry of
_
is square planar.
3) The molecular geometrv of the HeO+ ion is
4) The molecular qeometry of the CSr molecule is
5) The molecular geometry of the PHCI2 molecule is
_.
6) The F-B-F bond angle in the BF3 molecule is
4
Th" F-N-F bond angle in the NF3 molecule is slightly less than
-.
8) The electron-domain geometry of the AsF5- ion is octahedral. The hybrid orbitals used by the As atom for
bondine
are
orbitals.
o bond(s) in the molecule below.
9) There is/are
H H
-
llll..
.|.!-_
l"
:O:
o--H
I
H
bonding is _.
A) regions of electron density on an atom will organize themselves so as to maximize s-character
B) electron domains in the valence shell of an atom will arrange themselves so as to minimize repulsions
C) atomic orbitals of the bonding atoms must overlap for a bond to form
D) regions of electron density in the valence shell of an atom will arrange themselves so as to maximize
10) The basis of the VSEPR model of molecular
overlap
E) hybrid orbitals
11)
will form
as necessary to, as closely as
possiblg achieve spherical symmetry
According to VSEPR theory, if there are three electron domains in the valence shell of an atom, they will be
arraneed in a(n)
seometrv.
A) linear
B) trigonal bipyramidal
C) trigonal planar
D) tetrahedral
E) octahedral
O-C-O bond angle in the CO32- ion is approximately
A) 90"
B) 120"
c) 60"
12) The
A-1
D) 109.5"
E) 180"
13) The molecular geometry of the BrO3- ion is
A) tetrahedral
B) trigonal pyramidal
C) T-shaped
D) trigonal planar
E) bent
14) The bond angles marked a, b, and c in the molecule below are
about
,
and
respectively.
:O: H :O:
lllll..
iriYc'rj-'o'-H
HPH
A) 109.5" 120",109.5o
B) 109.5" 90",120
c) 120" 120",94"
D) 90" 90o, 90o
E) 120",120",109.5"
15) Of the molecules below, only
A) BFs
.-*..-.._-
is nonpolar.
E) IFs
D) NF3
C) PBrs
B) BrCl3
16)Themo1eculargeometryofthePF3mo1eculeis'andthismoleculeis-'
A) trigonal planar, nonPolar
B) tetrahedraf unipolar
C) trigonal pyramidaf nonPolar
D) trigonal pyramidaf Polar
E) trigonal planar, Polar
l7)Theelectron-domain geometry of
a carbon-centered compound is
tetrahedral. The hybridization of the central
carbon atom is
A)
st'd
B)
sp
C)
sP342
D)
tP2
s) tP3
18)ThehybridizationsofnitrogeninNF3andNH3are-and.''respectively.
A) sp, sp3
19) A typical double bond
B) sp3,
sp3
C) sp2,
.-...-_.-.
A) is stronger and shorter than a single bond
B) imparts rigidity to a molecule
C) consists of traro shared electron pairs
D) consists of one o bond and one n bond
E) All of the above answers are co$ect.
A-2
sp2
D) sp2,
sp3
E)
st''
sp
20) Which of the following molecules or ions
NqA)
NH4+
will exhibit delocalized bonding?
N3-
NH4+ and N3-
B) NO2- only
q Nq-,
NH4+, and N3-
D) N3- only
E)
NQ- andN3-
21) The hybridization of the carbon atom labeled x in the molecule below is
HH:O:X
I ll //.I C_C_O_H
H _N_
I
H_C_H
I
H
A)
sp
B)
s/
C)
sp3
D)
sp36
E) sp362
22)The more unpaired electrons in a species, the stronger is the force of magnetic attraction. This is called
23)UsingtheVSEPRmodel,themoleculargeometryofthecentralatominPF5isA) square planar
B) trigonal bipyramidal
C) seesaw
D) tetrahedral
E) square pyramidal
24)The hybrid orbital set used by the central atom in NOg- is
A)
sdd2
B)
sd
C)
sp2
A-3
--*.
D)
"dd
D
sp
,:a: :
r
,'qgi
-r':#
*€f;
-.,
t
'' .:.-
:-.-.
:
eL;
I
-
your responses to these questions will be scored on the basis of the accuracy and relevance of the information citedExplanations should be ciear and well orgamzed.Examples and equations rnay be included in your respon$es where
appropriate. Specific answers are preferable to broad, diffuse responses.
-
t'
!fr.'
"V
Use the infonrration in the table below to respond to the statements and questions that
should be in terms of principles of molecular structure and intermolecular forces.
Compound
Formula
Lewis Electron-Dot Diagram
Ethanethiol
cH3cH2sH
n:e te : S;H
Ethane
cH3cH3
II:C: C:tt
Ethanol
cH3cH20H
HH
H:e:e:b:H
HH
Ethyne
czllz
follow' Your answers
HH
HH
HH
HH
9p \outr
Paftbr
(a)DrawthecompleteLewiselectron.dotdiagramforethyne.iru*e-aFpr6pEiat@.
(b) Which of the four molecules contains the shortest carbon-to-carbon bond? Explain.
(c) A Lewis electron-dot diagram of a molecule of ethanoic acid is given below. The carbon atoms in
molecule are labeled x and y, respectively.
the
t9,t H
U
,9 t C,, d.rt H
H
Identify the geometry of the arrangement of atoms bonded to each of the following.
(i)
(ii)
Carbon
r
Carbon y
goes into breaking
bonds." Is the statement true or false? Justify your answer.
(d) Energy is required to boil ethanol. Consider the statement "As ethanol boils, energy
bonds,
C-H
(e) Identify
(f)
bonds,
C-O
bonds, and
O-H
C-C
a compound from the table above that is nonpolar. Justify your answer.
Ethanol is completely soluble in water, whereas ethanethiol has limited solubility in water" Account for the
difference in solubilities between the two compounds in terms of intermolecular forces'
1) The electron-domain geometry of the AsF6- ion is octahedral. The
bondine
are
hybrid orbitals used by the As atom for
orbitals.
is square planar.
2) The molecular geometry of
3) The molecular geometry of the BtO3- ion is
A) trigonal pyramidal
B) T-shaped
C) trigonal planar
-
D) bent
E) tetrahedral
4) For a molecule with the formula AB2 the molecular shape is
5) The F-N-F bond angle in the NF3 molecule is slightly less than
6) The hybrid orbital set used by the central atom in SO2 is
A)
sp36
B)
I sp
sp342
q'1
and this molecule is
7) The molecular geometry of the PF3 molecule is
A) trigonal pyramidaf nonpolar
B) trigonal planar, nonpolar
C) trigonal planar, polar
D) tetrahedral, unipolar
E) trigonal pyramidaf polar
D) rp3
-
8) A trrpical double bond
A) consists of one cr bond and one n bond
B) is stronger and shorter than a single bond
C) imparts tigtdity to a molecule
D) consists of tlt'o shared electron pairs
E) All of the above answers are correct.
9) The O-C-O bond angle in the CO32- ion is approximately
A)
109.5'
B)
120'
C)
180"
D)
90'
E) 60'
10)Thehybridizationofthecarbonatomlabeledxinthemoleculebelowis-.
HH:O:X
I I ll //..
H-N- C-C-O-H
"r"
H-C-H
I
H
A)
sp
B) sp2
C) sp3
D)
sp34
g
sp342
11) The more unpaired electrons in a species, the stronger is the force of magnetic attraction. This is called
B-1
o bond(s) in the molecule below'
L2) There is/are
H
-
H
:O:
lll..
t:-_
l"
c---+I
I
I
H
13) The molecular geometry of the PHCI2 molecule is
14) The
electron-domain geometry o{ a carbon-centered compound is tetrahedral. The hybridization of the cerrtral
carbon atom is
--.
A) sp
C) sP3
B) sP2
D) sp3d
15)ThehybridizationsofnitrogeninNF3andNH3are-and,respectively.
D) sp3, sp
C) tf, tp3
B) rt', tp3
A) rp, sp3
16) 1/hich of the following molecules or ions
NOZ- NH4+
A) NH4+
and
E) sp3d2
E)
sf,
sp2
will exhibit delocalized bonding?
N3-
N3-
B) NO2- only
NO2-, NH4+, and N3D) N3- only
E) NO2- andN3C)
17) The molectrlar geometry of the H3O+ ion is
18)
Of the molecules below, oniy
B) BF3
A) BrCl3
--'
is nonpolar.
C) PBr3
D) NF3
E) IFg
model of molecular bonding is
----.
A) electron domains in the valence shell of an atom will arrange themselves so as to minimize repulsions
B) regions of electron density on an atom will organize *remselves so as to maximize s-character
C) hybrid orbitals will form as necessary io, as closely as possiblq achieve spherical symmetry
D) regions of electron density in the valence shell of an atom will arrange thernselves so as to maximize
19) The basis of the VSEPR
overlap
E) atomic orbitals of the bonding atoms must overlap for a bond to form
B-2
20) According to VSEPR theory
arranged in
a(n)
if there are three electron domains in the valence shell of an atom, they will be
geometry.
A) linear
B) trigonal planar
C) trigonal bipyramidal
D) octahedral
E) tetrahedral
21) The F-B-F bond angle in the BF3 molecule is
22)1"le bond angles marked
respectively.
a,
_.
b, and c in the molecule below are
about
:o: H :o:
..lllll..
:-rTYffi-'e-H
HUH
A) 120" 120o,90"
B) 90o, 90",90"
c) 120o,I20",709.5"
D) 109.5", 120o,109.5o
E) 109.5.,90",720o
23) Using the vsEPR
model the molecular geometry of the central atom in pF5 is _
A) square pyramidal
B) square planar
C) seesaw
D) tetrahedral
E) trigonal bipyramidal
24)The molecular geometry of the CS2 molecule is
_.
B-3
.
and
ffi
Compound
Fomrula
Lewis Electron-Dot Diagram
Ethanethiol
cH3cH2sH
HH
n:e:e:3:H
HH
HH
Ethane
cH3cH3
H:C:e;n
Ethanol
cH3cH2oH
fr;e :C:O:H
Ethyne
c$z
HH
HH
(a) Draw the complete Lewis electron-dot diagram for
HH
9p \CIur
wib{
ethynei
v-e.
(b) Which of the four molecules contains the shortest carbon-to-carbon bond? Explain.
-<
(c) A Lewis electon-dot diagram of a molecule of ethanoic acid is given below. The carbon atoms in the
molecule are labeled x and y, respectively
..'9' H
H:O:C":Cr:11
H
Identify the geometry of the arangement of atoms bonded to each of the following.
(i) Carbon r
(ii) Carbon y
(d) Energy is required to boil ethanol. Consider the statement "As ethanol boils, energy goes into breaking
bonds,C-H bonds, C-O bonds, aud O-H bonds.o' Is the statement true or false? Justiff your answer.
C-C
(e) Identify a compound from the table above that is nonpolar. Justify your answef.
whereas ethanethiol has limited solubility in water. Account for tbe
difference in solubilities between the two compounds in terms of intermolecular forces.
(0 Ethanol is completely soluble in water,
\-