Exam
Name___________________________________
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
1) Atoms w ith the same number of protons but different numbers of neutrons are called
1)
__________.
Answ er: isotopes
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
2) W hich of the follow ing elements does this electronic configuration represent?
2)
1s 2 2s 2 2p5
A) C
B) O
C) Al
D) N
E) F
Answ er: E
3) How many unpaired electrons are present in the isolated carbon atom (atomic number = 6)?
A) none
B) one
C) tw o
D) three
3)
E) four
Answ er: C
4) W hich of the follow ing is the electronic configuration of the element Fe?
4)
A) 1s 2 2s 2 2p6 3s 2 3p6 4s 2 3d6
B) 1s 2 2s 2 2p8 3s 2 3p6 4s 2 3d6
C) 1s 2 2s 2 2p6 3s 2 3p6 4s 2 4p6
D) 1s 2 2s 2 2p6 3s 2 3p8 3d6
E) 1s 2 2s 2 2p6 3s 2 3p6 4s 2 4d6
Answ er: A
5) The atomic number of bor on is 5. The cor rect electronic configuration of bor on is:
5)
A) 2s 2 2p3
B) 1s 2 2s 3
C) 1s 2 2s 2 3s 1
D) 1s 2 2p3
E) 1s 2 2s 2 2p1
Answ er: E
6) W hich of the follow ing statements cor rectly describes the third electron shell that surrounds
the nucleus of an atom?
A) The third shell can contain f orbitals.
B) The maximum number of electrons that can occupy the third shell is 18.
C) The third shell contains only s and p atomic orbitals.
D) The total number of atomic or bitals present in the third shell is 16.
E) All third shell elements must have d electrons.
Answ er: B
1
6)
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
7) Ar , K+ , Cl- are isoelectronic elements (elements w ith the same number of electrons).
7)
W hat or bital does the last electron occupy?
Answ er: 3p orbital
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
8) The compound methylamine, CH3 NH2 , contains a C-N bond. In this bond, w hich of the
8)
follow ing best describes the charge on the nitrogen atom?
A) +1
B) -1
C) slightly negative
D) slightly positive
E) uncharged
Answ er: C
9) W hich of the compounds below bond predominantly via ionic bonding?
9)
A) CF4
B) NH3
C) KCl
D) both A and B
E) both B and C
Answ er: C
10) W hat type of bonding is most impor tant in CH3 CH2 CH2 CH2 CH2 CH3 ?
A) polar
B) ionic
C) hydrogen
10)
D) covalent
Answ er: D
11) W hich of the follow ing contain(s) polar covalent bonds?
11)
A) NH3
B) H2
C) KF
D) Na 2 O
E) both A and C
Answ er: A
12) W hich of the follow ing covalent bonds has the largest dipole moment?
A) C-H
B) C-O
C) H-N
Answ er: E
2
D) C-C
12)
E) H-F
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
13) Using the symbol
+and
-, indicate the direction of the polarity in the indicated bond.
13)
Answ er:
14) Covalent bonds may be polar or nonpolar. W hat property of the atoms for ming a given
14)
bond determines this?
Answ er: electronegativity
15) Provide the mathematical equation for the dipole moment of a bond, and identify the
15)
variables.
Answ er: µ = e × d, w here µ is the bond dipole moment, e is the amount of charge w hich is
separated, and d is the distance over w hich the charge is separated.
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
16) The formal charge on nitrogen in the compound below is __________.
A) -2
B) 0
C) +1
D) -1
Answ er: C
3
16)
E) +2
17) W hich of the follow ing is the most likely electronic structure for C2 H2 ?
17)
A)
B)
C)
D)
E) H
C
C
H
Answ er: E
18) W hich of the follow ing structures, including for mal charges, is cor rect for diazomethane,
CH2 N2 ?
A)
B)
C)
D) :CH2
N
N:
E)
Answ er: E
4
18)
19) W hat are the for mal charges on nitrogen and the starred oxygen atom in the follow ing
19)
molecule?
A) N = -1, O = -1
B) N= +1, O = 0
C) N = -1, O = 0
D) N = +1, O = +1
E) N = +1, O = -1
Answ er: B
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
20) Draw the Kekulé structure for each of the follow ing:
a. CH3 CH2 OH
b.
CH3 CHO
20)
c. (CH3 )3 C+
Answ er:
21) The Kekulé structure of pentane is show n below . Draw the condensed structural
for mula w hich cor responds to this Lew is structure.
Answ er: CH3 (CH2 )3 CH3
5
21)
22) Draw condensed structures for the four compounds w ith for mula C3 H9 N.
22)
Answ er: CH3 CH2 CH2 NH2
CH3 CH2 NHCH3
(CH3 )2 CHNH2
(CH3 )3 N
23) W rite a Lew is structure for the molecule given and show all formal charges.
23)
CH2 CO
Answ er:
24) Expand the condensed structure below to show the covalent bonds and the lone-pair
24)
electrons.
(CH3 )2 CHCH2 CHO
Answ er:
25) Draw the Lew is structure for CH3 N2 + .
25)
Answ er:
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
26) How many distinct and degenerate p or bitals exist in the second electron shell, w here n = 2?
A) 0
B) 1
C) 2
D) 3
E) 4
Answ er: D
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
27) Draw the shape of a 2p or bital.
27)
Answ er:
6
26)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
28) Consider the interaction of tw o hydrogen 1s atomic or bitals of the same phase. W hich of the
statements below is an incorrect description of this interaction?
A) The molecular or bital formed has a node betw een the atoms.
B) The molecular orbital formed is cylindrically symmetric.
C) A maximum of tw o electrons may occupy the molecular or bital for med.
D) The molecular or bital for med is low er in energy than a hydrogen 1s atomic or bital.
E) A sigma bonding molecular orbital is formed.
Answ er: A
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
29) Both sigma ( ) and pi ( ) bonds can be for med by overlapping p or bitals. Describe the
29)
difference.
Answ er: Sigma bonds are for med from the overlap of atomic or bitals along a circular axis
of symmetrical nature, i.e., head-on overlap. All single bonds are sigma bonds.
Pi bonds are for med from the overlap of atomic or bitals along a
non-symmetrical (parallel) axis, i.e., side-to-side overlap. Double and triple
bonds contain both sigma and pi bonds.
30) W hat kind of molecular or bital ( ,
*,
, or
*) results w hen the tw o atomic or bitals
30)
show n below interact in the manner indicated?
Answ er:
*
31) W hat kind of molecular or bital ( ,
*,
, or
*) results w hen the tw o atomic or bitals
31)
show n below interact in the manner indicated?
Answ er:
32) W hat kind of molecular or bital ( ,
*,
, or
*) results w hen the tw o atomic or bitals
show n below interact in the manner indicated?
Answ er:
7
32)
28)
33) W hat kind of molecular or bital ( ,
*,
, or
*) results w hen the tw o atomic or bitals
33)
show n below interact in the manner indicated?
Answ er:
*
34) W hat kind of molecular or bital ( ,
*,
, or
*) results w hen the tw o atomic or bitals
34)
show n below interact in the manner indicated?
*
Answ er:
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
35) Choose the cor rect hybridization for the atom indicated in the molecule below .
35)
CH3 CH2 CH2 CH3
A) sp
B) sp3
C) sp2
D) none of the above
Answ er: B
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
36) W hat or bitals are used to form the covalent bonds in butane (CH3 CH2 CH2 CH3 )?
Answ er: The carbon-carbon
36)
bonds are for med by the overlap of tw o carbon sp 3 hybrid
atomic or bitals. The carbon-hydrogen
bonds are for med by the overlap of a
carbon sp3 hybrid atomic or bital and a hydrogen s or bital.
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
37) W hich carbon(s) in the follow ing molecule is (are) sp hy bridized?
A) carbon 2
B) carbons 4
C) carbon 1
D) carbon 4, 5
E) carbons 1, 3
Answ er: D
8
37)
38) W hich of the follow ing is an sp 2 hybridized car bon?
38)
A) · CH3
B)
C) CH3
D) A and B
E) A, B and C
Answ er: C
39) W hat is the predicted shape, bond angle, and hybridization for + CH3 ?
39)
A) trigonal planar, 120°, sp2
B) trigonal pyramidal, 109.5°, sp2
C) trigonal pyramidal, 120°, sp2
D) trigonal planar, 120°, sp3
E) trigonal planar, 109.5°, sp2
Answ er: A
40) W hat or bitals overlap to create the H-C bond in CH3 + ?
A) s-sp3
B) sp2 -sp3
C) s-sp2
40)
D) sp3 -sp3
E) s-p
Answ er: C
41) The lone-pair electrons of the methyl anion occupy a __________ orbital.
A) sp2
C) sp3
B) s
D) p
41)
E) sp
Answ er: C
42) W hich of the follow ing is closest to the C-O-C bond angle in CH3 -O-CH3 ?
A) 109.5°
B) 180°
C) 160°
D) 120°
42)
E) 90°
Answ er: A
43) Each lone pair of electrons on the O atom in methanol (CH3 OH) occupies a(n) __________
43)
orbital.
A) sp2
C) sp3
B) s
D) p
E) sp
Answ er: C
44) The N-H single bond in methyl amine (CH3 NH2 ) is a __________ bond formed by the overlap
of a __________ orbital on N and a __________ on H.
A)
; sp2 ; p
B)
; sp3 ; s
C)
;p;p
Answ er: B
9
D)
; sp2 ; s
E)
; sp3 ; s
44)
45) Triethylamine [(CH3 CH2 )3 N] is a molecule in w hich the nitrogen atom is __________
45)
hybridized and the CNC bond angle is __________.
A) sp3 , >109.5°
B) sp, 109.5°
C) sp2 , <109.5°
D) sp2 , >109.5°
E) sp3 , <109.5°
Answ er: E
46) The N-H bond in the ammonium ion, NH4 + , is for med by the overlap of w hat tw o orbitals?
A) sp3 -sp2
B) sp2 -s
C) sp3 -s
D) sp3 -sp3
46)
E) sp2 -sp2
Answ er: C
47) Among the hydrogen halides, the strongest bond is found in __________ and the longest bond
47)
is found in __________.
A) HF, HF
B) HF, HI
C) HI, HI
D) HCl, HBr
E) HI, HF
Answ er: B
48) W hich bond in the follow ing molecule is the shortest?
A) bond 1
B) bond 2
C) bond 3
48)
D) bond 4
E) bond 5
Answ er: E
49) W hich of the follow ing species have tetrahedral bond angles?
49)
A) A and E
B) A, B and E
C) A, D, E and F
D) D only
E) A, D and E
Answ er: C
50) The carbon-carbon double bond in ethene is __________ and __________ than the
carbon-car bon triple bond in ethyne.
A) stronger; longer
B) stronger; shor ter
C) w eaker; shor ter
D) w eaker; longer
E) stronger; more polar
Answ er: D
10
50)
51) W hat is the CNN bond angle in the compound show n below ?
A) ~90°
B) ~60°
C) ~180°
51)
D) ~120°
E) ~110°
Answ er: D
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
52) Draw the structure of a molecule w hich contains only carbon and hydrogen atoms
52)
(only three of w hich are carbon) and in w hich tw o of the carbons are sp 2 hybridized
and the ot her is sp hybridized.
Answ er: H2 C
53) W hy is the C
C
CH2
H bond in ethene (H2 C
CH2 ) shor ter and stronger than the C
H bond in
53)
ethane(CH3 CH3 )?
Answ er: The length and strength of a C
H bond depends on the hybridization of the
carbon atom. The mor e s character in the hybrid or bital used by carbon to form
the bond, the shor ter and stronger the bond. This is because an s or bital is closer
to the nucleus than is a p. Ethene uses carbon sp2 hybrid or bitals (1/3 s character)
to make its carbon-hydrogen bonds w hile ethane uses carbon sp3 (1/4 s
character).
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
54) W hich of the follow ing molecules does not exhibit a net dipole moment of zero?
A) CO2
B) CCl4
C) CH4
Answ er: E
11
D) SO3
54)
E) H2 O
55) W hich of the follow ing molecules has a net dipole moment of zero?
55)
A)
B)
C)
D)
E)
Answ er: C
56) W hich of the follow ing molecules has the smallest dipole moment?
A) HCl
B) HBr
C) HI
D) Br 2
56)
E) NH3
Answ er: D
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
57) BF3 has a dipole moment of zero. Propose a structure for BF3 that is consistent w ith
this information.
Answ er: BF3 is trigonal planar.
12
57)
58) Draw the Kekulé structure and show the direction of the dipole moment for CH2 Cl2 .
58)
Answ er:
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
59) W hich of the follow ing is not a conjugate acid-base pair?
59)
A) NO3 - , NO2 B) H2 O, HOC) HSO4 - , H2 SO4
D) - OH, O2E) H2 O, H3 O+
Answ er: A
60) W hat is the product for med from the follow ing acid-base reaction?
60)
A) CH2 OH + + NH3
B) CH3 O- + + NH4
C) CH3 OH2 + + - NH2
D) CH3 NH2 + H2 O
E) CH4 + NH2 OH
Answ er: B
61) The conj ugate acid of H2 O is:
A) H2 O+
B) H3 O
61)
C) H3 O+
D) HO-
E) H3 O-
Answ er: C
62) W hich of the follow ing ions is the strongest acid?
A) H3 O+
B) H-
62)
C) H2 O
D) HSO4 -
E) HO-
Answ er: A
63) W hich species act as bases in the follow ing reaction?
A) 2 and 4
B) 3 and 4
C) 1 and 2
Answ er: A
13
63)
D) 2 and 3
E) 1 and 3
64) W hat is the conj ugate acid of NH3 ?
A) - NH2
B) + NH3
64)
C) - NH
D) + NH4
E) + NH2
Answ er: D
65) W hat is the conj ugate acid of CH3 NH2 ?
A) NH2 -
65)
B) CH3 NH3 +
C) NH4 +
D) CH3 NH-
C) CH3 NH-
D) NH2 -
Answ er: B
66) W hat is the conj ugate base of CH3 NH2 ?
A) CH3 NH3 +
66)
B) NH4 +
Answ er: C
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
67) Give the conj ugate acid and the conj ugate base for HSO4 - .
67)
Answ er: conj ugate acid: H2 SO4
conj ugate base: SO4 2-
68) W rite a completed equation for the acid-base pair show n below .
68)
HCO2 H + - NH2
Answ er: HCO2 H + - NH2
HCO2 - + NH3
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
69) W hat is the pH of a 0.1 M solution of HCl? (Note: pKa for HCl is -6.)
A) -1
B) 6
C) -8
D) -6
69)
E) 1
Answ er: E
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
70) If H2 O has a pKa value of 15.7 and HF has a pKa value of 3.2, w hich is a stronger base,
70)
HO- or F- ? Explain.
Answ er: HO- is a stronger base than F- because HF is a stronger acid than H2 O, and the
stronger the acid the w eaker its conj ugate base.
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
71) W hich of the follow ing is the strongest acid?
A) CH3 NH3 +
B) CH3 OH
71)
C) H2 N-
Answ er: D
14
D) CH3 OH2+
E) CH3 NH2
72) The pKa of CH3 COOH is 4.8 and the pKa of HCOOH is 3.8. Given this infor mation, one know s
72)
that __________.
A) HCOO- is a w eaker base than CH3 COOB) CH3 COOH completely ionizes in w ater
C) CH3 COOH reacts w ith HO- w hile HCOOH does not
D) HCOOH reacts w ith HO- w hile CH3 COOH does not
E) HCOOH is a w eaker acid than CH3 COOH
Answ er: A
73) W hich of the follow ing is the strongest acid?
A) CH3 OH
B) CH4
73)
C) H2 O
D) :NH3
E) HF
Answ er: E
74) W hich of the follow ing is the strongest acid?
A) CH3
C
74)
CH
B) CH3 CH2 OH
C) CH3 OCH3
D) CH3
NH
CH3
E) CH3
CH
CH2
Answ er: B
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
75) Consider the set of compounds, NH3 , HF, and H2 O. Rank these compounds in or der of
increasing acidity and discuss your rationale.
Answ er: NH3 < H2 O < HF
W hen determining relative acidity, it is often useful to look at the relative
basicity of the conj ugate bases. The stronger the acid, the w eaker (mor e stable,
less reactive) the conj ugate base. In this case, one w ould look at the relative
basicity of F- , OH- , and NH2 - . The relative strengths of these species can be
gauged based on the electronegativity of the charged atom in each base. Since
fluor ine is the most electronegative, F- is the most stable, least reactive base in
the group. This means that its conj ugate acid, HF, is the strongest.
15
75)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
76) W hich of the follow ing is the strongest acid?
A) I
B) II
76)
C) III
D) IV
E) V
Answ er: E
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
77) Explain w hy :NF3 is a w eaker base than :NH3 .
77)
Answ er: Fluor ine has an electron w ithdraw ing effect that reduces the availability of the
pair of electrons on nitrogen. Thus the basicity of :NF3 is less than that of :NH3 .
78) W ould you predict trifluoromethanesulfonic acid, CF3 SO3 H, to b e a stronger or w eaker
78)
acid than methanesulfonic acid, CH3 SO3 H? Explain your reasoning.
Answ er: Trifluor omethanesulfonic acid is a stronger acid. Compare the strengths of the
conj ugate bases and remember that the w eaker the base, the stronger the
conj ugate acid. In the case of the trifluor o derivative, the presence of the highly
electronegative fluor ine atoms serves to delocalize the negative charge to a
greater extent. This additional delocalization makes trifluor omethanesulfonate a
w eaker base.
79) W hich of the follow ing anions, CH3 CHBrCO2 - or CH3 CHFCO2 - is the stronger base?
Explain y our choice.
Answ er: CH3 CHBrCO2 - is the stronger base. The mor e electronegative F atom can mor e
effectively delocalize the negative charge via induction. This greater
delocalization stabilizes CH3 CHFCO2 - relative to CH3 CHBrCO2 - and makes it a
w eaker base.
16
79)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
80) The pKa of CH3 COOH is 4.8. If the pH of an aqueous solution of CH3 COOH and CH3 COO- is 4.8,
80)
then one know s __________.
A) CH3 COOH is completely unionized
B) [CH3 COOH] > [CH3 COO- ]
C) CH3 COOH is completely ionized
D) [CH3 COOH] < [CH3 COO- ]
E) [CH3 COOH] = [CH3 COO- ]
Answ er: E
81) W hen a small amount of hexanoic acid [CH3 (CH2 )4 CO2 H, pKa~4.8], is added to a separator y
81)
funnel w hich contains the or ganic solvent diethyl ether and w ater w ith a pH of 2.0, it is found
mainly in the __________ phase as __________.
A) w ater; CH3 (CH2 )4 CO2 B) ether; CH3 (CH2 )4 CO2 H
C) w ater; CH3 (CH2 )4 CO2 H
D) ether; CH3 (CH2 )4 CO2 E) none of the above
Answ er: B
82) W hen a small amount of hexanoic acid [CH3 (CH2 )4 CO2 H, pKa ~4.8], is added to a separator y
funnel w hich contains the or ganic solvent diethyl ether and w ater w ith a pH of 12.0, it is found
mainly in the __________ phase as __________.
A) ether; CH3 (CH2 )4 CO2 H
B) ether; CH3 (CH2 )4 CO2 C) w ater; CH3 (CH2 )4 CO2 H
D) w ater; CH3 (CH2 )4 CO2 E) none of the above
Answ er: D
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
83) At w hat pH w ill 25% of a compound w ith a pKa of 5.3 be in its basic for m?
83)
Answ er: 4.8
84) The amino acid glycine (H3 N+ CH2 CO2 H) has tw o acidic Hs, one w ith pKa = 2.34 and
the ot her w ith pKa = 9.60. Draw the structure of the for m of glycine that predominates
at a pH of 12.
Answ er:
17
84)
82)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
85) Buffering is used to maintain the pH of human blood in the relatively narrow 7.3 - 7.4 range.
W hat acid/base pair serves to b uffer the blood?
A) H2 O / HO-
B) HCl / Cl C) H2 CO3 / HCO3 D) NH4 + / NH3
E) H3 O+ / H2 O
Answ er: C
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
86) Explain w hy AlCl3 is a Lew is acid.
86)
Answ er: A Lew is acid is an electron pair acceptor . Aluminum in AlCl 3 has an empty p
or bital that can accommodate the pair of electrons provided by a Lew is base.
18
85)