Test Bank to Accompany AP Chemistry [7th ed.] 9780618730148

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The

ation of the compound ICJ d heat of fori11 . the standar 58. Using the following data, calculate · · I) in kJ/mol: Af{° {kJ/rno .

242.3

Cl2(g) ~ 2Cl(g)

Use

To c To c Con

Iz (g) ~ 2l(g) ICl(g) ~ I(g) + Cl(g) lz(s) ~ lz(g) 62.8 A) B)

C)

D) E)

-211 kJ/mol -14.6 kJ/mol 16.8 kJ/mol

245 kJ/mol 439 kJ/mol

Ans: C

w;ror PbO(s)

59. Using the information belo'.'7, calculate PbO(s) + CO(g) ~ Pb( s) + C02(g) for COi{g) =-393.5 kJ/mol

m; m;for CO(g) =-110.5 kJ/mol

A) B) C)

-151 .6 kJ/mol -283.0 kJ/mol +283.0 kJ/mol Ans: A .

Lill· = -13l .4 kJ

,· D) E)

-372.6 kJ/mol +252.1 kJ/mol

60. For w?ich of the following reaction(s) is the enthalpy change for the reaction not equal ,to /ill r of the product? . I. 2H(g) ~ H2(g) II. H2(g) + Oz(g) ~ H202(]) Ill. HzO(l) + O(g) ~ HzOz(l) A) I B) II C) Ill D) I and III E) II and III Ans: D 61 . Consider the following reaction: 2Al(s) + 3C)i(g) ~ 2AICh(s)· AflA) ls the reaction exothermic ore ct' h - -1390.81 kJ , n ot enni ? B) Calculate the heat produced wb c. 1 C) How many grams of Al are e_n 0.0 g AICh fonns Ans: A . . required to produce 1.00 kJ

100

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. of energy?

Cop

e Nature of Energy

e the following to answer questio~·s 62-63:

carry out the reaction N2 + 202 ~ 2NO2 requires 67.7 kJ. carry out the reaction N2 + 202 ~ N2O4 requires 9.7 kJ. · nsider the reaction 2Nq2 ~ N2O4. 62. How much energy (absolute value) is involved in the reaction 2NO2 ~ N2O4? Ans: 58.0' kJ ·· I 63 . ls the reaction endothermic or exothermic? Ans: exothermic 64. Consider the following data: Af-J (kJ)

Ca(s) + 2C(iaphite) ~ CaC2(s)

-62.8

Ca(s) + 1/2O2(g) ~ CaO(s)

-635.5

CaO(s) + 820(1)_~ Ca(OH)2(aq)

-653.1

. C2H2(g) + (5/2)O2(g)

~

2CO2 + H2O(l)-1300

C(graphite) + O2(g) ~ CO2(g)

-393 .51

Use Hess's law to find the change in enthalpy at 25°C for the following equation: CaC2(s) + 2H2O(l)

~

Ca(OH)2(aq) + C2H2(g)

Ans: -713 kJ

65 . Consider the following standard heats of formation: P4O10(s) =-3110 kJ/mol H2O(l) = -286 kJ/mol H3PO4(s) = -1279 kJ/mol Calculate the change in.enthalpy for the following process: P4O1o(s) + 6H2O(l) ~ 4H3PO4(s) Ans: -290 kJ

true

66. The following statements concerning petroleum are all except: A) It is a thick, dark liquid composed mostly of hydrocarbons. B) It must be separated into fractions (by.boiling) in order to be used efficiently. C) Some of the commercial uses of petroleum fractions include gasoline and kerosene. D) It was probably formed from the remains of ancient marine organisms. E) All of its hydrocarbon chains contai.n the same number of carbon atoms: Ans: E

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101

67

·

68.

69.

buried and exposed to e t wer tha . f Jants · he remains o p . . This fossil fuel was formed frorn t . E) gasobne. · f rne It 1s opane, 1 · . el fuel. D) pr high pressure and heat over A) coal. B) natural gas. C) dies · Ans: A . d. ·1 ble per unit burne _is The coal with the highest energy ava1 a D) antprac1te. . I ·n· energy valu·e : 1 A) lignite. E) They are equa B) subbituminous. C) bituminous. Ans: D . nhouse effect are true except: All of the following statements about th e gree · A) It occurs only on earth. . rtant role in retaining the atmosphere's B) Toe molecules HiO and CO2 play an impo heat. . . h b k 1·nto space. C) Low humidity allows efficient radiat10n of ea! ac_ · st D) The carbon dioxide content of the atmosphere ts qmte able. E) a and d Ans: E

70. One of the main advantages of hydrogen as a fuel is that

A)

the only product of hydrogen combustion is water. B) it exists as a free gas. C) it can be economically supplied by the world's oceans. D) plants can economically produce the hydrogen needed. E) it contains a large amount of energy per unit volume of hydrogen gas. Ans: A 71. Which of the following is not being considered as an energy source fior th e· fiuture ? A) ethanol B) methanol C) seed oil D) shale oil E) b d' 'd . ·

Ans: E

·

.

car on 1ox1 e

72. Ac~tylene (C2H2) and butane (C4Hio) are gaseous fuel

. , . available from the combustion of a given s. Determme the ratio of energy 1 temperature and pressure using the fioll ~o udme of acetylene to butane at the same owmg ata· . Th e change m enthalpy of combustion fi · The _change in enth_alpy of combustion f~~ C2H2(g) == -49.9 kJ/g. Ans. About 2.21 times the volume of ace . C4Hrn ==-49.5 kl! a given volume of butane tylene 18 needed to furn· h. hg. · · ts t e same energy as

73. A property that is independent of the . th Ans: False pa way ts called an in

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. tensive property.

The Nature of Energy

74. In exothennic reaction, potential energy stored in chemical bonds is being .converted to thennal energy via heat. · Ans: True 75 . A state function·does not depend on the system's past or future. Ans: True 76. When a system perfonns work on the surroundings, the work is reported with a negative sign. · Ans:. True . 77. The change in enthalpy can always be thought of as equal to energy flow as heat. Ans : False

78. The specific heat capacities of m~tals are relatively low. Ans: True 79. The _____ of a system is the .sum of the kinetic and potential tnergies of all the particles in the system. Ans: True 80. _____ involves the transfer of energy between two objects due to a temperature difference. Ans: True 81. On a cold winter day, a steel metal fence post feels colder than a wooden fence post of identical size because · A) The specific heat capacity of steel is higher than the specific heat capacity of wood. B) The specific heat capacity of steel is lower than the specific heat capacity of wood. C) Steel has the ability to resist a temperature change better than wood. D) The mass of steel is less than wood so it loses heat faster. E) Two of the above statements are true. Ans: B

\

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103

'--•utpcer 6

of th e

universe is constant.

. the energy odynam1cs, t 82. According to the first la~ ~f berme ual to zero? . . . d to [actors hke friction and Does this mean that •gE 1s always . q . by q === -WA) Yes •gE = 0 at all times, which is wbut this is only ue . ' qua! zero ' . B) "No, •gE does not a1ways e h system's mtemal energy I o because it refers to t e ' heat. C) No, •E does not always equa zer , . on the system orb which is affected by heat and work. k is always being done Y D) No •gE never equals zero because wor h ' t flowing between t e system th e sys em. ergy is always , E) No, •gE never equals zero because en and surroundings. Ans: C 83. Consider the reaction: 2CIF3(g) + 2NH3(g) -t N2(g) + 6Hf:(g) + Cli(Hg)o ~ N not important? 0 . th • H why 1s the •gv f 1or 2 t I I Wh en ca cu a mg e g RXN, t d no energy is needed for this A) Because nitrogen is in its standard elementa1sta e an · · product to exist. -· · 1· "bl B) Because any element or compound in the gaseous state reqmres a neg igi e amount of energy to exist. 0 C) B_ecause the products are not included when calculating •gH_RXN. D) Because nitrogen is in its elemental state and does not contribute to the reaction itself. E) Two of the above statements explain why N2 is not important when calculating 0 •gH RXNAns: A 84. Which of the following statements is/are true?

I. q (heat) is a state fun~tion because ~H is a state function and q = L\H: II. When ?0.0 g of alummum at 20.0°C is placed in 50.0 mL of water at 30.0oC, the H20 will undergo a smaller temperature change than the I . (Th d . f ·fi heat capacity . of H o = a ummum. e ensity o H2O -- 1.o g/mL , spec11c J/oC . . 4 2 18 of aluminum = 0.89 JIOC•g) . , · •g, specific heat capacity III. When a gas is compressed, the work is ne f . work on the system and energy flows out gfatihve smce the surroundings is doing 0 . e system IV . For the reaction (at constant pressure) 2N ( ) · 2 g + 50 2(g) h I . h 2N · ent a PY 1s t e same whether the reaction tak 20 5(g), the change ID . ~ steps. es place In one step or in . of A) I, II, IV D)· a senes B) II, III II, IV C) II, III, IV E) All of th b Ans: D . e a ove statements are true.

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TheNature of Energy 85. Consider the reaction: N2(g) + 3H2(g) ~ 2NH 3(g) Assuming this reaction takes place in an ·elastic balloon with an atmospheric pressure of · 1.0 atm and that you have a-stoichiometric mixt~re of nitrogen and hydrogen , draw a microscopic diagram before and after the reaction occurs. See the example below to ea2+ > er > K+ Ans: A .36. Which of the following types of molecules has a dipole moment (when polar bonds are present)? . A) linear molecules with two ident_ical bonds B) tetrahedral molecules (four identical bonds equaily spaced) C) trigonal pyramid molecules (three identical bonds) D) trigonal planar molecules (three identical bonds equally spaced) E) None has a dipole moment. Ans: e 37. Given the following infonnation: of sublimation ofLi(s), = 166 kJ/mol Li(s) -t Li(g) bond energy ofHCI = 427 kJ/mol HeJ(g) -t H(g) + Cl(g) ionization energy of Li(g) = 520. kJ/mol Li(g) -t Li\g) + e. electron affinity of Cl(g) = -349 kJ/mol eJ(g) + e- -t er(g) lattice energy of LiCl(s) = -829 kJ/mol Li\g) + er(g) -t Liel(s) of H2 = 432 kJ/mol bond energy H2(g) -t 2H(g) A) · 363 kJ B) -562 kJ e) -179 kJ D) ~ 73 kJ E) None of these Ans : B

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135

Chapter 8 econd electron affinity and the s

38. The first electron affinity value for oxygen is - value is · . · . rable (exothermic) . ble (endotherJlllC) A) unfavorable (endotherrmc), favo · · ) nfavora B) unfavorable (endotherrmc , u thennic) C) favorable (exothennic), favorabl~~ e(~ndotherJlllC) D) favorable (exothennic), unfavora e E) More infonnation is needed. Ans: D 39. Choose the molecule with the strongest bond · . 1 A) F 2 B) Ch C) Br2 D) Ii E) All·are equa. Ans: B 40. Choose the molecule with the strongest bond. ' A) HF B) HCl C) HBr . D) HI E) All are equal. Ans: A . 41. Choose the molecule with the strongest bond. A) CH.t B) H2O C) NH 3 D) HF E) All are equal Ans: D 42. Which of the following molecules exhibits the greatest bond energy? A) F 2 B) Ch C) Br2 D) Ii E) all the same . Ans: B 43. As the number of bonds between two carbon atoms increases, which one of the following decreases? · A) number of electrons between the carbon atoms B) bond energy C) bond length D) all of these E) none of these Ans: C

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Resonance 44. Using the following bond energies Bond Bond Energy (kJ/mol)

C=C C-H

839 413

O=O 495 C=O 799 O-H 467 estimate the heat of combustion f~r one mole of acetylene: C2H2(g) + (5/2)O2(g) ~ 2CO2(g) + H 2O(g) A) 1228 kJ B) -1228 kJ C) -447 kJ D) +447 kJ Ans: B

E) +365 kJ

45. Which of the following species ~ould be expected to have the lowest ionization energy? 2 · A) F B) Ne C) 0 · D) Mg2+ E) Na+ Ans: C 46. Which of the following has the smallest radius? 2 2 A) F B) Ne · C) O ~ D) Mg + E) Na+ Ans: D 47. Which of the following ionic compounds has the largest lattice energy (the lattice energy most favorable to a stable lattice)? A) BaO B) BeO C) Cs!' D) NaBr E) BaS Ans: B 48. In which of the following compounds does'the bond between the central atom and bromine have the greatest ionic character? A) LiBr B) KBr C) SeBr2 D) AsBr2 E) CaBr2 · Ans: B 49. Which of the following species is best described by drawing resonance structures? A) PH 3 B) NH/ C) 03 D) SO3- E) HCN Ans: C 50. Using the following data reactions .

Afl° (kJ) H2(g) + Cli{g) ~ 2HCl(g)

-184

H2(g) ~ 2H(g)

432

Cl2(g) ~ 2Cl(g)

239

A) 770 kJ

B) 856 kJ

G)

518 kJ

D) 326, kJ

E) 428 kJ

Ans: E

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137

51. Given the following bond energies C-C C=C C-0 C=O C-H 0-H

0-0

347 kJ/mol 614 kJ/mol 358 kJ/mol 799 kJ/mol 413 kJ/mol 463 kJ/mol 146 kJ/mol

-

+ CH OH -t H2CO + 2H20. estimate Aff for the reaction H202 kJ 3 D) +199 kJ E) +345 A) -345 kJ Ans: A

B) -199 kJ

C) -l0 5

kJ

52. Given the following information N 2 bond energy= 941 kJ/mol F 2 bond energy = 154 kJ/mol

Ml° =-103 kJ/mol 3 .!_ N 2(g) + F2-(g) -t NF3(g) 2 2 A) D) 66 kJ/mol 113 kJ/mol B) 268 kJ/mol E) none of the~e C) 317 kJ/mol Ans: B Use the following to answer questions 53-55: Using the following electronegativity values C 2.5 Cl 3.2 H 2.2 N 3.0

0

3.4

select from the following group the molecule that fits the given statement: CH3CHO a) b) CO2 c) CH3Cl d) C2H6 e) none

53. This molecule contains a carbon atom with tri 0 · Ans: a) CH 3CHO , g na! planar geometry. 54. This molecule is the most polar. Ans: a) CH3CHO

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on Mt4'a,

Resonance

55. This molecule shows the smallest number oflone pairs in its Lewis structur(!. Ans: d) C2H6 . 56. As indicated by Lewis structures, which of the following would probably not exist as a stable molecule?

B) CH2O

A) CH3OH Ans: C

C) CH 3O

D) C 2H2 E) C3~

57. Which pf the following molecules is non-polar oyerall? A) Sf4 B) SF2 C) CC4 D) H2S E) OCh Ans: C 58. Select the best Lewis structure for acetone, CH3COCH3. A)

H I

•• ••

H I

H-C-C=O-C-H

I H

I H

B)

:0: II

H

I

H

I

H-C-C-C-H

I H

I H

C)

H I

..

••

I

••

I

H-C-C-O-H-C-H

H

H

D)

H .

••

I

H-H-C=C=O-C-H I

I

H

H

E) H H H I I I H-C-C-C=O I

I

••

H H Ans, B

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'-- 11

ctpter 8

most to least polar? der for molecules from 59. Which of the following is the corr~r ~rcc1zH2 A) CRi > CF2Ch > CF2H2 > C 4 > cc1zH2 B) Clti > CF2H2 > CF2Cli > C~ Cfu == CC4 C) CF2Ch > CF2H2 > CCbH2 -CC4 4 D) CF2H2 > CChH2 > CF2Cb ~ CH ~ Cfu 2 E) CF2Ch > CF2H2 > CC4 > CChH Ans: D est bond angle? th 60. Of the following, which molecule has e larg A) 03 B) OF2 C)

HCN

D) - H2O b d angles E) More than one of the above have equally 1arge on . · Ans: C 61. ·According to the V.SEPR modei, the arrangement of electron pairs around NH3 and

are A)

CHi

. different because in each case there are a different number of atoms around the central atom. B) different because in each case there are a different number of electron pairs around the central atom. , C) the same because both nitrogen and carbon are both in the second period. D) the same because in each case there are the same number of electron pairs around the central atom. · E) different or the same, depending on the conditions leading to maximum repulsion. . Ans: D ·

62. The Cl-Kr-Cl bond angle in KrC4 is closest to A) 90° B)_ 109° C) 120° D) 150° E) 360°

Ans: A 63. Which of the following atoms cannot exceed th . A) N B) S C) p D) I E) All of th e octet rule ma molecule?

Ans: A

e atoms (a-d) can exceed the octet rule.

64. In the cyanide ion (C~, the nitrogen has A) -2 B) -1 C) o D) 2 E) 2 a formal charge of

Ans: C

65 . Which has the larger N-O bond length _ A) NO2'N02 orNQ3-?.

B)

NO3C) The bond lengths are the sam Ans: B e.

140

D) E)

More info . None of thrmation is needed. ese.(a-d)

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Coninan,, ••

Resonance · 66. · How many of the followi D)ng molecules-SF2, SF4, SF6, ·SiO2--,are polar? A) o B) I C) 2 3 E) 4 Ans: C 67. Which of the following exhibits resona~ce?

A)- CH4 · B) · PC1 5 C) H2O D) NO2 E) At least two of the molecules (a-d) exhibit re.sonance.

Ans: D

.

68. How many resonance structures can be drawn for the molecule o 3? A) 1 B) 2 C) 3 D) 4 . E) 5 .I Ans: B 69. As_indicated by Lewis structures, which of the following species could probably not

exist as a stable molecule? . A) NH3 B) N2H2 C) N2Ri Ans : D

D) N2H6 E) N2O4

70. Choose the electron dot formula that most accurately describes the bonding in CS 2. · (Hint: Consider formal charges.) · A) o)

:s=c=s: ••

H

B)

:C=S=.:):

C)

:~-C-~:

=~-e=~=

E)_

••

••

:~-C=S:

•.

Ans: A 71. Which of the following has a Lewis structure most like that of co/-? A) CO2 B) so/ - C) NO3- D) 03 E) NO2

Ans: C

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141

-?

afd resonanc 72. Which of the following is not a v 1

...'"" for NJ · e strllcu.... -

A)

B)

C)

D)

7 . 'i-i==N==N l.!· .u E) all are correct Ans: A 73. In the Lewis structure for elemen~ nitrogen ~)ere ~:e~paired electrons. A) a single bond between the mtrogens. B) a double bond between the nitrogens. E) none of the above.

C) a triple bond between the nitrogens. Ans:C 74. Complete the Lewis structure for the molecule: CH3 0

I

I

CH3-CH-C-C-N

This molecule has _ _ _ _ single bonds and---- multiple bonds. A) 4, 2 B) 6, 3 C) 11 , 5 D) 11, 2 E) 13, 0 Ans:D Use the following to answer questions 75-77: Draw the Lewis structures of the molecules below and use them . to answer the followmg questions: . I. II. lll. IV. V.

BH3 N02 SF6 03

PCls

75. Which of the molecules obeys the O t A) I B) II C) lil D) lV E) c~t rule? Ans: D

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76 · How many of the molecules have no dipole moment? A) 1 B) 2 C) 3 D) 4 E) they are all polar . . Ans: C

77. Which of these molecules show resona~ce? A) I, II B) II, IV C) II, V D) III, IV E) Ill, V Ans: B 78. The force between two bodies having identical electric charges

A) B)

is a force ofrepulsion. . is a force ofrepulsion if the charges are negative, and one of attra~tion if they are positive. increases as the bodies are moved farther apart. is. independent of the distance between them. is directly proportional to the distance between them.

C) D) E) Ans: A

Use the following to answer questions 79-81 : .Consider the compound crotonaldehyde, whose skeleton is

H H H H I

I

·1

I

H-C1-CrC3-C4-0 . I

H 79. How many electrons must be shown in the Lewis structure of this .molecule? A) 12 B) 18 C) 24 D) 28 E) 32 . Ans: D

80. How many nonbi:mding electrons appear in the Lewis structure of this molecule? A) 2 B) 4 C) 6 D) 8 E) 10

Ans: B 81 . Which carbon in this molecule has tetrahedral bonding? A) 1 B) 2 C) 3 D) 4 E) all Ans: A 82. Which of the.following molecules contains a double bond?

A) CO2

B) NH3

C) H20

D) all

E) none

Ans: A

Co

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- - - - - - - - - - - - - - - - -~ - - - - - - - - - -- ~ -- - - -- .. ,cr8 . . orange liquid forms that is a vile smeJling ·ng could be the correct 'th chlorine gas,. f the foJloWI . O 83. When molten sulfur reacts wi ula sci. Which •• found to have the empirical fonnd? · ~l ·s·:.::::g-Cl . . mpoun · ) L, •• " th Lewis struc~e for is co . D '11 U_g-CI A) ~-~1: E) B) ~=~l 0

:£I-~ •• ..

~=£1-~1=~=

C)

Ans: E

85 84 sti0 Use the following to answer que ns - : Given the following Lewis structure: H H H

I I

I

2

4

H2C=C-C=C-CH3 3

5

nt in this molecule?

.

84. How many unshared pairs of electrons are prese A) 0 B) I C) . 2 D) 3 E) 4 Ans: A

85. How many electrons are shared between carbons 1 and 2? A) 0 -B) 2 C) 4 D) 6 E) 8 . Ans: C 86. Which of the following compounds contains only one unshared pair of_valence electrons? A) NH3 B) H20 C) CH.t D) NaCl E) BeF3 Ans: A 87. In the reaction between magnesium and sulfur the magn · esmm atoms . , A) become amons. C) beco , . . B) · become cations. me part of polyatom1c 10ns. Ans: B D) share electrons with sulfur.

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Resonance 88. The Lewis structure for HBO . A) 3 3 IS H-l>==B-0-H I

••

:0: I H

B)

H-l> ••

B==l>-H II

:O

I H

C)

H-L)-B-6-H I

:O: I H

D) H-L>___:B-6-H ••

I

•·O• I• H · E) H-L>=B-{5-H ••

I

·o, •I • H

Ans: D

89. In the Lewis structure for !Ch-, how many lone pairs of electrons are around the central iodine atom? A) 0 B) I Ans: D

C) 2

D) 3

E) 4

90. In the Lewis structure for SF6, the central sulfur atom shares_·_ _ _ _ electrons. A) 4 B) 8 C) 10 D) 12 E) none of the ab_ove, because SF6 is an ionic compound Ans: D

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145

Use the following to answer questions -91-9Z: Consider the following mole~ules. I.BF3 II.CHBr3 (C is the central atom) lll.Br2 IV.XeCli

v.co VI.SF4 Select the molecule(s) that fit the given statement. 91. These molecules violate the octet rule. A) I, II, IV B) I, Ill, IV, VI C) m; V, VI D) I, IV, VI E) I, II, IV, VI Ans; D

92. These molecules have a zero net dipole moment. A) Ill, V B) I, III, IV C) Ill, IV, V D) I, III, IV, VI E) none of them Ans: B 93. Which of the following Lewis structures best describes BF3?

A)

·F· ;·

:l'-B

":F:

B)

C)

F: :f-B/

":F:

D)

·F·

:f-1:J; .

.. ":F:

E)

r. /. :t-B

Ans: A

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Resonance

94. Which 'o f the followin m ' · , A) XeF2 B) BeCl2 g ct~cules has_a nonlinear structure? 3 D) CO2 E) N2O (central atom is N) Ans: C . Use the following to answer ques1ions 95-100:

Select the correct molecular structure for th . . · · , pyramidal e given species from the choices below: _ a) b) c) d) e)

none of these octahedral trigonal planar bent

95. SOCl 2 Ans: a) 96. OF 2 Ans : e) 97. NCb Ans: a)

98. XeF/ Ans: a) 99. BrF/ Ans: c)

100. Beh Ans: d)

is

IO 1. The geometry of AsC1 5 A) trigonal bipyramidal. B) square pyramidal. C) distorted tetrahedral. Ans: A

D) E)

octahedral. none of these

102. How many of the following molecules or ions are linear? NH4+ HCN CO2 NO2 · NH3 A) 0 B) 1 C) 2 D) 3 E) 4 Ans : C

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147

d molecule, H2C=O, are . the ronnaJdehy e

10 bon atom . . 103 The bond angles about th e car . about: 090 D) I goo E) 90~ A) 120° B) 60° C) l Ans: A I are nonlinear? 104. Which of the following molec~ esHCN CO2, H202 . E) 11 I' N , D). 1 .N Nza are mear , 3' 3 N02- C2H2, o - H 02 A) C2H2, HCN B) CO2, N3- C) N 2' 2 Ans: C

X OF2 molecule have? 105. What type of structure does the e h d D) trigonal planar E) octahedral A) pyramidal B) tetrahedral C) T-s ape Ans: C

·

. · I b'pyramid structure? 1 · h 106. Which of the following species has a tngona A) NH3 B) Ifs C) h- D) PCls E) none oft ese Ans: D 107. The bond angle in H2Se is about: A) 120° B) 60° C) 180° D) 109° E) 90° Ans: D

108. Which ion is planar? A) NH.i+ B) co/ - C) Ans: B

so/-

D) CI03- E) all are planar

Use the following to answer questions 109-116: Select the co~ect molecular structure for the given species from the choice~ below: a) pyramidal · b) tetrahedral c) square planar d) octahedral e) none of these 109. pp6Ans: d) l 10. PCI/ Ans: b)

111. XeF6 Ans: e)

148

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Resonance 112. Nh Ans: a)

113. SiH4 · Ans: b) 114. ClO2 . Ans : ,e)

115. IF4Ans : c) 116.

so/ Ans : a)

117. Which of the following has an incomplete octet in its Lewis structure? A) SO2 B) ICI C) CO2 D) F2 E) NO Ans: E

Use the following to answer questions 118-125: Select the correct molecular structure for the given species from the choices below: a) linear b) trigonal planar c) tetrahedral d) bent e) none of these

118. H2O Ans : d) 119. CO2 Ans: a) 120. BeC]z

Ans: a) 121. SF4 Ans: e) 122. NO/ Ans: b

0

H ghton Miffli n Company. All rights reserved. · ht © C opyrig C OU . .

149

'-'•u11,1cer 8

123. l3Ans: a) 124. PFs Ans: e) 125. ClF Ans: d)

·

h

· . ound Xe and what 1s t e · 0 f electrons surr 126. In the molecule XeF2, how many pairs molecular geometry? . D) 5 bent E) 6, linear A) 4, bent B) 4, pyramidal C) 5, lmear ' Ans: C • c. · pecies bas a square planar 11 127. According to VSEPR theory, which of the 10 owmg s .· · molecular structure? A) TeBr4 B) BrF3 C) IFs D) Xef4 E) SCh Ans: D 128. How many of the following molecules have all of their atoms in the same plane?

H2C=CH2 F20 H2CO NH3 A) 3 B) 4 C) 5 D) 6 E) 7 Ans: C

CO2 , Be€h

129. Which of the following sets has elements with the most nearly identical atomic radii? A) Cr, Mn, Fe, Co D) Be, B, C, N

B) C)

E)

Mg, Ca, Sr, Ba Ne, Ar, Kr, Xe

C, P, Se, I

Ans: A 130. When nonmetals chemically combine they tend t0 fi

Ans: covalent

'

131 . In spite of larger electronegativity di'flie

h

·

orm w at type of bond?

b . . . rences etween b d d dipole while SC1 2 does. Explain fully. on e atoms, BeCh has no Ans: See Sec. 8.3 ofZumdahl, c·i.e . 11 m1stry.

150

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Resonance Use the following to answer questions 132 _135 : For each of the following compounds: a) draw the Lewis structure b) give the shape of the molecule c) indicate the polarity of the molecule

132. AlF3 · Part A:

.\/. ·F· · ·F· I

:F: Part B: trigonal planar Part C: nonpolar 133. NH3

Part A:

H-~-H H

t

Part B: pyramidal Part C: polar

134. IC1 4Part A:

•• . :CI: I ••

t ..

J-

Cl-..J-Cl: •• I •• I :Cl:

Part B: pyramidal Part C: polar

135. CBrh Part A:

:Br: I 1· :r-c-. : ••

I

••

t

.. tetrahedral :I:

Part B: Part C: polar

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151

Chapter 8

a covalent bond is formed.

136. When a metal reacts with a nonmetal . . g of a pair of electrons the unequal shann . . 137. A nonpolar covalent bond results from between atoms in a molecule. ' Ans: False . t. nuclear charge mcreases. · · · creases as tfi e · 138. The size in a series of isoelectromc ions m Ans: False Ans: False

. h two pairs of electrons. 139. A double bond occurs when two atoms s are . Ans: True 140. The.shape of an ammonia molecule is tetrahedral. Ans: False 141 . The shape of a carbon dioxide molecule is iinear. Ans: True 142. The Lewis structure for CHCh has 9 Ione electron pairs. Ans: True 143. The ability of an atom in a molecule to attract shared electrons to itself is called Ans: electronegativity 144. A molecule that has a center of positive charge and a center of negative charge is said to be _ _ _ _. . Ans: dipolar 145. The _ _ _ _ is the change in energy that takes place whe · · are packed together to form an ionic solid. . n separated gaseous ions Ans: lattice energy

·l 46 .. The--,--- of a molecule shows how th . the atoms m the molecule. Ans: Lewis structure

·

e va1ence el t _ec rons are arranged among

147. Stable molecules usually contain atoms that h Ans: valence . ave filled

. - - - orbitals.

.· 148. When several nonequivalent Lewis stru tu is used to determine the most appropria~ s:es can be drawn for a Ans: formal charge ructure(s). molecule, _ _ _ __

152

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.

.

n l\11fflin C ornpany ,

.

d · All riehts .-eserve ·

Resonance

149. Which of the following st t

. . . . b . a ements are true concernmg . tome bondmg? . 1 nd omc o mg occurs between a metal which has a high affinity for electrons, and a nonmetal which I 1 ' . ' oses e ectrons relatively easy. 2 CaCh forms because Ca + is always a more stable species than the calcium atom alone. /

A)

B) C)

Compounds with ionic bonds tend to have low melting points. · !he elect~onegativity difference between the bonding atoms of ionic compounds IS small smce the electrons are not shared but rather held together by electrostatic forces. All of the above statements are false.

D)

E)

Ans: E

I 50. Consider the following drawings below:

H-f.=

H-N-H H

:b=C=O: . .

W hich of the following statements are true? I. The electrons in each molecule tend to orient themselves around the most electonegative element. II. Each molecular drawing follows the localized electron model. III. Both HF and CO2 are linear molecules and therefore polar. l V. T he bond angles of NH 3 are slightly less than I 09 .5° because the lone pair compresses the angles between the bonding pairs.

A) B) C) D)

I, Ill, IV I, II, IV I, II, Ill · · II, IV .

E) All of the.above statements are correct. Ans: B

151. If a compound has a number of individual dipoles, then I. it is polar overall. II. there is an electronegativity difference between the bonded atoms. lll. it is ionic. IV. it doesn't have resoQance. A) II only

B) C) D) E)

II, IV I, II, IV I Ill .

,

All of the abo~e statements are correct.

Ans: A

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153

t_;hapter 8

· izes Justify your . t their relative s . that represen 152. Match the ions }?elow with the pictures · answers. Ions:. 2 Ca + Se2. K+ . Ga 3+

00000 00000 Ans:

K+ ·

Ca2+

Ga3+

Se2-

Br -

3+ 2+ C d G Se2- and Br- each have the electron configuration of Kr. K , a , an a each 2 have the electron configuration of Ar. The Se - and Bf contain electrons in_a higher energy level, therefore making their radii larger ~an ~e other three ions. 2 Since Bf has more protons, this will draw the electrons m slightly more than Se 3 (due to a slightly higher effective nuclear charge). For the -other three ions, Ga + will be the smallest because it has the highest number of protons. K + has the least number of protons and is thus the biggest ion of the three.

.

+

153. Consider the following reaction: A2 + B2 ~ 2AB LIB= -285 kJ The bond energy for A2 is half the amount of AB. The bond energy ofB 2 = 432 kJ/mol. 'What is the bond energy of A 2? . . · A) 717kJ/mol D) -143kJ/mol B) 478 kJ/mol E) none of these C) 239 kJ/mol · Ans: C

154

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. n l\11fflin C

ornpan

,

.

- - ~ - - - -- - - - - - - - - - - - - - - - - -__::_Y..:.·::! A!! ll..!J ri:ght reserved-

CHAPTER9 Hybridi~ation and the Localized Electron Model 1. The htbridizati~n of the phosphorus atom in the cation PH2+ is: . A) sp B) sp C) dsp D) sp E) none of these · Ans: A 2. In the molecu_le C2H.i the valence orbitals of the carbon atoms are assumed to be .. A) not hyb~~ized. D) sp3 hybridized. B) sp hybnd1zed. E) dsp hybridized. 2 C) sp hybridized. Ans: C 3. Which of the following statements is (are) incorrect? I. The hybridization of boron in BF3 is sp2. II. The molecule XeF4 is nonpolar. III. The bond ordernfN2 is three. IV The molecule HCN has two pi bonds and two sigma bonds. A) All four statements are correct. D) II and III are incorrect. E) II, III, and IV are incorrect. B) II is incorrect. C) I and IV are incorrect. Ans: A 2 4. Ato~s which are sp hybridized form __ pi bond(s). A) 0 B) I C) 2 D) 3 E) 4 Ans: B 5. The hybridization of the central atom in XeF/ is: 3 2 3 2 A) sp B) sp C) sp3 D) dsp E) d sp Ans: E 1 6. The hybridization of the central atom in CIF/ is: A) sp B) sp2 C) sp3 D) dsp3 E) d2sp3 Ans: ·c

7. The hybridization of the central at~m in h }: 3 ,A) sp B) sp2 C) sp3 D) dsp E) d sp Ans: D

··rn·

Company. AJJ rights reserved. . Copyright © Houghton M1 .m ·

155

- - - - - - - - - - - - - - - - - - - - : - - - - -- - - - ,

- --r·'-• y

· O is·

8. The hybridization of the central at~m ~) J2s~3 3 2 A) sp B) sp C) sp D) dsp · Ans: B · b ene is trUe? 9. Which of these statements about enz 3h bridized. A) All carbon atoms in benzene are sp Y . d b tween C atom,s. . B) Benzene contams only 1t bon s e in benzene Is 1.5. . nd C) The bond order of each C-C bo th t displays ionic bondmg. 1 D) Benzene is an example of a molecu e a E) All of these statements are false. Ans: C 2 · . ith sp hybridization? 1 IO. Which of the following m,olecules contams a centra atom w A) , :Cl:

H

H-

I Al I

-

H

I .. P - Cl: I .. :~l:

B)

:F

'\ . .. /B - ~:

:f. C) H

H -

I ?. -

H

D)

E) :~l - Be - ~I:

Ans: B 11. What hY.bridization is predicted for the nitr A) sp2 B) sp3 C) sp3d D) sp3d2 E)ogen atom in the No3-ion? Ans:. A none of these ·

156

Copyright© llought

on Mifflin Corn - - - - - - - - -- - - - - - - - - - - - - - - -.......:.i:~a:.!! n:v_.

AJI -.:~a..•~ -~~,. ..."'ed,

Hybridization and the Localized El · ectron Model • , , . 12. Which of the following d . A) H co ' oes not contam at least one pi bond? 2 B) COi C) C2Ri D) C3Hs th E). All of e above (a-d) contain at least one pi bond. Ans: D 13. Consider the following Lewis structure H O H H I

II

I

I

H-C-C-C==C-H

I

H Which statement about the molecule is false? A) There are 10 sigma and 2 pi bonds. B) C-2 is sp2 hybridized with bond angles of 120°. 3 C) Oxygen is sp hybridized. D) This molecule contains 28 valence electrons. E) There are some H-C-H bond angles of about 109° in th~ molecule. Ans: C 14. Which statement aboutN 2 is false?

A) B)

It is a gas at room temperature. The oxidation .state is +3 on one N and -3 on the other. C) It has·one sigma and two pi bonds between the two atoms. D) It can combine with H2 to form _NH3. E) It has two pairs of non bonding electrons. Ans: B

15. Consider the following Lewis structure:

H I

H I

I

H

!1 H

0 sp3 sp sp ,2 sp sp

·c-1 sp3 . sp2 sp sp3 sp3

H I

H-c-o-c-c=c-c=N-H

A) B) C)

D) E) Ans: A

C-2 , sp3 sp sp sp2 sp2

C-4 sp2 sp sp2 sp3 sp

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157

9 Use the following to answer questions 16-1 : . bridization choices: Consider the molecule and the followtng hy H O Cl

I

II

I

.

H-c-c-c-c=N

I

H a) b) c)

d) e)

I

H

_sp 2 sp 3 sp 3 dsp d2sp3,

16. What is the hybridization of the carbon atom that is double bonded to oxygen? ·Ans: b) · 17. What is the hybridization of the carbon atom that is bonded to chlorine? Ans: c) 18. What is the hybridization of the nitrogen atom? Ans: a) 19. What is the hybridization of the oxygen atom? Ans: b) 20. The hybridization ofl in IF4-is A) sp B) sp2 C) dsp3 D) dsp3 E)' d2sp3 Ans: E 21. The hybridization of Cl in ClF + . A) 2 IS 2 sp B) . sp C) sp3 D) dsp3 E) d2sp3 Ans: C

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oughton

i 01..

Hybridization and the Localized El ectron Model 22. Consider the molecule 0

II

H2C=CH-C-CH2-C=N I

2

3

4

Specify the hybridization of each ~arbon at om. A) . B) C)

D)' E) Ans: A

C-1 sp2 sp2 sp2 sp2 sp2

C-2 sp2 sp2 sp2 sp2 sp

C-3

C-4 sp3 sp3 sp3 sp3 sp2

. sp2 sp2 sp3 sp3 sp

C-5 sp sp3 sp2 sp3 sp

23. The hybridizat~on of the central atom, Al, in A1Br3 is 3 3 2 3 A) sp B) sp C) sp D) dsp E) d sp Ans: B 24. The hybridization of Se in SeF6 is 2 2 3 3 3 A) sp B) sp C) sp D) dsp E) d sp Ans: E 25. The hybridization of Br in BrF3 is 3 3 A) sp B) _sp2 C) sp D) dsp Ans: D 26. What is the bond order ofNe2? A) 0 B) 1/2 C) I D) I 1/2 Ans: A

2 3 E) d sp

E) 2

27. What is the bond order of C2+7 A) 0 B) 1/2 C) I D) I 1/2 E) -2· Ans: D 28. Which of the following has .the greatest bond strength?· A) B2 B) 0 2- C) CN- D) O/ E) NOAns: C 29. The hybridization of the lead atom in PbCl4 is 3 2 2 A) dsp B) sp C) ct2sp D) s1id E) none of these Ans: -E 30. The hybridization of the central atom in N03- is 2 A) p3 B) sp2 C) sp D) sp d E) sp Ans: B

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159

Chapterg

31. Which of the following statements is false? A) C 2 is paramagnetic. . · cH3CH3. B) C2 is diamagnetic. on er than the on~ in H CH 3 2_ . 3 C) The carbon-carbon bond ~n C22_ ~s s~ort!r than the one in C ' D) The carbon-carbon bond m C2 ts s E) Two of the above. Ans: A . . din in benzene, C6H6? 32. How many electrons are involved mpt bon g A) 12 B) 30 C) 3 D) 6 E) 18 Ans: D

Use the following to answer questions 33-35: Tetracyanoethylene has the skeleton shown below: _ N

N

\

I

C \

I

I

C

I C-C

\

C

C

\

N

N

From its Lewis structure determine the following: 33. How many sigma and pi bonds are in the molecule? A) 5 sigma and 9 pi D) 9 sigma and 9 pi B) 6 sigma and 8 pi E) 5 sigma and 8 pi C) 9 sigma and 7 pi Ans:D 2

34. How many of the atoms are sp hybridized? A) 2 B) 4 Ans: A

C) 6

D) 8 E) 10

35. How many of the atoms are sp hybridized? A) 2 B) 4 C) 6 D) 8 E) 10 Ans:D

160

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ton ~1.irn· •n Corn

ff~bridization and the Localized Electron Model 36. In which of the compound b' I · 2 sp3) for carbon? . s e ow ts there more than one kind of hybridization (sp, sp ,

I. IL

CH3CH2CH2CH 3 CH3CH ~ CFICH 3

Ill. CH2 =CH-CH= CH 2 IV. H-C=C-H A) II aniIII B) II only C) lII and IV D) I and IV . E) III Ans: B 37. Complete the Lewis structure for the following molecule: CH3 O .

I I CH3-CH-C-C-N

This molecule has _ _ _ _ sigma and _ _ _ _ pi bond~: A) 4, 5 B) 6, 3 C) 11, 5 D) 13, 2 E) 13, 3 Ans: E 38. Which of the following substances contains two pi bonds? A) C2H4 B) C3Hs C) C2H2 D) C2H6 E) C~ Ans: C ' 39. Which of the following molecules has a bond order of 1.5? A) 0/ B) N 2 C) 0 2- D) C2 E) none of these Ans: C 40. Consider the molecule C 2H4. The hybridization of each C ato_m is 3 3 3 2 A) sp B) sp C) sp ·o) dsp E) d2sp ·

Ans: B Use the f~llowing _to answer questions 41-42: Consider the skeletal structure shown below: N-C.-C-N Draw the Lewis structure and answer the following: 41. How mapy of the atoms are sp hybridized? A) O B) 1 C) 2 D) .3 E) 4 Ans: E 42. ~ow many pi bonds does the molecule contain? 7 6 A) 0 B) 2 C) 4 D) E)

Ans: C

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I 61

'--uapter 9

BN is false?

bout the molecule o i bonds. 43 Which of the following statements a D) It h~S tw p re true · · ll Of these a · A) It is paramagnetic. E) A ·_ · B) Its bond order is 2. . 12 C) The total number of electrons ts · Ans: A

?

b t the species G~ is fal~e. d 44. Which of the followin~ statements a ou C) It has two pt bon s. A) It is paramagneqc. . D) All oHhese are true. 4 1 B) The total number of electrons is · Ans: A .

.

?

45. Which of the following statements is true_. . MO . nd A) Electrons are never found i~ an 8?ttbo mgh the atomic orbitals of which they B) , All antibonding MOs are higher Ill energy t an C)

:t~i::a::dMOs have electron density mainly outside the space between the two

nuclei. D) None of the above is true. E) Two of the above statements are true. Ans: E

46. Which of the following molecules contains the shortest C- C bond? A) C2H2 B) C2~ Ans: A

C) C2H6 D) C2Clt E) b and d

47. Which of the nitrogen-containing molecules below is paramagnetic in its lowest energy

state? A) N2

B) NO

C) NH3 D) N2~

E) none of these

Ans: B

48. If four orbita.ls on one atom overlap four orbitals on a se d t h . ~on a om, ow many molecular orbitals will form? A) 1 B) 4 C) 8 D) 16 E) none of these Ans: C 49. Which of the following molecules or ions · ' . + is not paramag t· . . A) 02 B) 02 C) B2 D) NO E) F ne IC m Its ground state? 2 Ans: E 50. For which of the following diatomic m 1 1 . . o ecu es w Id h an e1ectron 1s removed, 1.e., if the molecul . ou t e bond order b · ter if state? e 1s converted to th . . ecome grea A) B B) c C) p D) F e positive ion in its ground Ans: 2D 2 2 z E) Na2 . .

162

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. n l\11ffiin Con,

Hybridization and the Localized El ec tron Model

51. The configuration (cr2s)2c 2 *)2( 2 1 the ground state of cr s 7t PY) (n2px)l is the molecular orbital description for

A) Li/ Ans: C

B) Be2 C) B2 D) B/ - E) C 2

52. Which of the following species is paramagnetic? A) C2 B) B2 C) N2 · D) H2 E) none of these . Ans: B 53. Which of the fo!lowing s~ecies has the largest dissociation energy? A) 02 B) 0 2 C) 0 2 - D) o/ E). o/+ Ans : E 54. The fact that 02 is paramagnetic can be e~plained by A) the Lewis structure of 0 2. D) the molecular orbital diagram for 0 2, E) hybridization of atomic orbitals in B) resonance. 02. C) a violation of the octet rule. Ans: D 55. For how many of the following does the bond order decrease if you add one electron to

the neutral molecule? B2, C2, P2, F2 A) 0 B) 1 C) 2 D} 3 E) 4 Ans: C 56. The hybridization of a molecule is measured to determine the shape of the molecule.

Ans: False

57. As the bond order of a hon? increases, the bond energy ___ and the bond length A) B) C)

D) E)

increases, increases decreases, decreases increases, decreases . . decreases, increases More information is needed to answer this quest10n.

_ Ans: C 58. Which of the following diatomic molecules has a bond order of2? A) B2 B) C2 C) P2 D) F2 E) Na2 · Ans : B 59. Which of the following h2as the larg;st bond ~~der? . A) N2 B) N2· C) N2 - D) N2 E) N2 Ans: A

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163

~uapcer 9

.

·

0 level diagrams for 2

and NO. Which of the

.. . 60. Consider the molecular orbital energy following is true? ic · fNO. I Both molecules are paramagnet · th the bond strength 0 · f O · reater an II. The bond strength o 2 ts g d. t mic molecule. III. NO is an example of a homonuclear tao th ionization energy of NO+. Iler than e d IV · 0 IV. The ionization energy ofN ts smaD) and III J. E) I, II, an 11 nd A) I only B) I and II C) I a IV Ans: C . ?

0 N are paramagnetic.

.

61. How many of the followmg: F2, B2, 2, 2, A) 0 Ans:

B) 1 C) 2

D) 3 E) 4

.

.

.

c·

62. Order the following from shortest to longest bond: C2, B2, H2, N2 C2, B2, H2, N2 N H~N~C~~ ~ B) N2, C2, B2, H2 E) none of these C) C2, N2, H2, B2 Ans: A

63. Which charge(s) of 0 2would give a bond order of2.5? A) -2 B) -1 C) +1 D) two of these E) none of these Ans: C

64. For how many of the following does bond order decrease if you take away one electron from the neutral molecule? B2, C2, P2, F2 A) 0

B) 1 C) 2

D) 3 E) 4 .

Ans: D 65. Which of the following electron distributions am~ng ;h I· describes the NO molecule? e mo ecu1ar orbitals best 0'2s

A) B) C) D) E)

Ans: E

164

0'2s•

2 2 2 2 2

cr2pz

7t2py==n2px

2 2 2

2 2

4 4 4 4 4

7t2py• ==n2px•

2 2 I 2 2

4 4 3 2 I

Copyright © Hou h g ton Mimi..

cr2pz•

2 I 0 0 0

Hybridization and the Localized El t · ec ron Model 66. In the mole_cular orbital description of CO A) the highest energy I ' . . . B) · e ectrons occupy anttbonding orbitals. 1 SIX mo ecu)ar 0rb1ta}s contain electrons. C) there are two unpaired electrons. . D) the bond order is 3. E) All of the above are false Ans:. D ,. . 67. Consider t~e molecular orbital description of the No- anion. Which of the following statements 1s false? , A) No- is paramagnetic. B) No- is isoelectronic with CO. C) The bond energy in NO+ is greater than the bond energy in No-. D) The bond order in No- is 2. E) · Statements a through d are false. Ans: B 68. The bond order in the NO molecule is· A) I . B) 1.5. C) 2. D) 2.5. E) 3. Ans : D 69. The CO molecule has the bond order: A) 0 B) I C) 2 D) 3 E) 4

Ans: D

·

70. Which of the following statements (a-d) about the co/- ion is false? 2 A) The orbitals on the carbon atom are sp hybridized. · B) The ion is expected to be diamagnetic. C) One C-0 boi;id is shorter than the other. D) The ion has a total of24.electrons. E) All the above statements are true. Ans: C 71. The C---C-H bond angles in ethylene, C2H4, are 120°. What is the hybridization of the carbon orbitals? 1 2 Ans : sp 72. Which of the following has the shortest bond length? A)

o/-

B) 0 2 C) 02-

D) O/

.

Ans; D

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.

165

I

. sim lest amino acid: th p 73. Consider the structure of glycme, e H

0

I

II

H2N-C-C-OH

l

-

.

.

. the molecule. H h N and c atom m a) Indicate the hybridizations at eac . be moleculet b) What is the total number of bonds m_t the molecule? 10 nd c) What js the total number of 1t bo s Ans: a) N sp3 C2 sp3 C2 sp2 b) 10 bonds c) l 1t bond ·· . . d N Using molecular orbital theory, 74. Draw a molecular orbital diagram for 0 2 an 2· . . th explain why the removal of one electron in 02 strengthens bondmg, whtl~ e removal

of one electron in N2 weakens bonding. Ans: See Sec. 9.3 of Zumdahl, Chemistry 75. What is the bond order of He/? A) 0 B) 1/2 C) 1 D) 1 1/2 E) 2

Ans: B 76. The following statements concern molecules that require resona11ce. Which is true?

A) . B) C) D) E) Ans:

The pi bonding is most clearly delocalized. The sigma bon~ing is most clearly delocalized. Both the sigma and pi bonding are delocalized. The benzene molecule is best described by the MO theory. · · The benzene molecule is best described by the localized 1 t . d 1 A e ec ron mo e .

77. Consider the benzene molecule. Which of the fi0 II

is false?

· owmg statements about.the molecule

A) B) C)

All six C-C bonds are known to b . , • e eqmvalent 2 Each carbon atom 1s sp hybridized · The localized electron model must : k · . mvo e resonance to account for the six equal C - C bonds. D) It has _delocalized pi bonding in the mo] E) The p1 bonds of carbon involve 2 _ecule. Ans: E sp orbitals.

166

Copyright © H oughton l\iiffl·

tn Conu,~

Jiyl5riclizanon ana the Localized El

ectron Model

78. Give the bond order for ea h Of . c a) · iI the following: 2 b) H2+ c)

H2-

d) e) f)

CNCN CN+

Ans: a) 1

b) 0.5 c) 0.5 d) 3

e) 2 _5 f) 2

· 79. Which of the fol~owin§,are paramagnetic? 02 02 02 - B2 C2 N2 F2 CN- P2 Ans : 02 o/- B2 . 80. Explain the concept of delocalization of electrons in SO 3• Indicate how this idea relates to resonance. . Ans: See·sec. 9.5 ofZumdah1 Chemistry. 1

81. W~enever a set of eq.uivajent tetrahedral atomic orbitals is required it will adopt a set of sp orbitals. · Ans: True 82. The hybridization of the Bin BH 3 is sp Ans: False

3

.

83. The H2- ion ·is more stable than H2 since it has an additional electron to produce a net lowering ·o f energy. · Ans: False · 84. Larger bond order means greater bond strength.

, Ans: ]'rue 85. When an electron pair is shared·in the area centered on a line joining the atoms a s bond

is formed.' Ans: · True

·

86. According to MO theory, F2 should be diamagneJic.

Ans:. Ti:ue . . · t d with paired electrons. 87. Paramagnetism 1s assoc1a e . Ans: False 88. The bond order for CN- is 2. Ans: False

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167

- - - ...,.,, 'Y

I

. . 89. The mixing of native atomic orbitals Ans: hybridization

fi r bonding is called to form special orbitals o . • ·

·

the ~tomic orbital of which

. . en~rgy than 90. A(n) _ _ _ _ molecular orbital is lower m · ' it is ~omposed. Ans: bonding nding electrons and the number . O fb . · , the number o 91. _ _ _ _ is.the difference between ., . . of antibonding electrons divided by two. Ans: Bond order · d . tO the inducing magnetic field. 92. _ _ _ _ causes a substance to be-attracte m . Ans; Paramagnetism . · . d fi r certain molecules because the localized 93. The concept of _ _ _ _ is reqmre o . air of atoms in a eiectron model assumes electrons are located between a given P . molecule. Ans: resonance 94. The number of molecular orbitals formed is always _ _ _ _ the number of atomic

orbitals combined. Ans: the same as 95. When comparing Be2 and H2, _ I. Be2 is more stable because it contains both bonding and antibonding valence

electrons. II. H2 has a higher bond order than Be2. Ill. H2 is more stable because 'it only contains s15 electrons. IV. H2 is more stable because it is diamagnetic, whereas Be2 is paramagnetic. A) I, ll B) III only C) 11, II} D) II, III, IV E) III IV Ans: C ' 96., Consider three molecules - A, B, C. Molecule A has

. . , 3 has two more effective pairs (electron pa· a hybnd1zatton of sp . Molecule B irs around the 1 Molecule C consists of one cr bond and tw b c_entra atom) than molecule A. 0nd hybridization, bond angles, and an exampi°; s. Give the molecular structure, Ans: e or each molecule. Molecule A Molecule B Molecular Structure tetrahedral . 'Molecule C octahedral Hybridization . sp3 linear d2sp3 Bond Angles 109.5° sp Example 900, 1800 Clti 1-80° SF . 6

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Jlybridization and the Localiz d El e ectron Model

97. If a molecule demonstrates

. · the substance can hav~~~mag~etism, then · th the bond order is not h paired and unpaired electrons. it can be determined: w ole_number. it must be an ion Y~rawmg a Lewis structure.

I. II. Ill. IV. A) I, II B) I, II, IV C) II, III D Ans: D . , , ) 1 only E) all of the above are correct Use'the following to answer q~estions 98 _100 : Use the molecules below to answer the ~ext thr · ee questions. .

0 0 0 98. Which molecule(s) have equivalent C-C bonds throughout the mole.cule?

A) I B) II Ans: A

C) Ill

D) all of the above E) none of the above

99. Which molecule(s) have p orbitals that share an electron pair to create 1t bonding? A) I B) II C) III D) all of the above E) none of the abo~e

Ans: D . I 00. Which molecule(s) have at least one carb?n atom that is sp hybridized? A) 1 B) II C) III D) all of the above E) none of the above

Ans: E

101. Which of the following &tatements are incorrect? A) For the molecule NO, the molecular orbital model is preferred over the localized electroh model because NO contains an unpaired electron. .B) Electrons in antibonding orbitals wiJI cause a molecule to be paramagnetic. C) According to the molecular orbital model, when bonding occurs between ' hydrogen and bromine to make HBr, the Is orbital of the hydrogen atom no , longer exist_s. . . . . . D) Antibonding electrons are higher m energy than the atomic orbitals from which they came from. · . , E) At }east two ofthe above are mcorrect. Ans: B

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CHAPTER10 I

nd Carbon ~ Silicone: Network Atomic Solids , /

1. Which one of the followi d · · c. · . . ? ng ecreases as the strength of the attractive intermolecular 1orces mcreases. A) The heat of vaporization. B) The nonnal boiling temperature. C) The _exte~t o~ deviations from the ideal gas law. D) T?e subhmat1on temperature of a solid. E) The vapor pressure of a liquid. Ans: E .

2. Order the intermolecular forces (dipole-diP,ole, London Dispersion, ionic, and hydrogenbonding) from weakest to strongest . A) .dipole-dipole, London Dispersion, ionic, and hydrogen-bonding· · B) · London Dispersion, dipole-dipole, hydrogen-bonding, ionic C) hydrogen-bonding, dipole-dipole, London Dispersion, and ionic D) dipole-dipole, io:i;iic, London Dispersion, and hydrogen-l?onding E) London·Dispersion, ionic, dipole-dipole, and hydrogen-bonding Ans: B ' · ' 3. ,Hydrogen bonds account for which of the following observation? A) Hydrogen naturally exists as a diatomic molecule. B) Hydrogen is easily combustible with oxygen. C) Water molecules are bent or "V-shaped". D) Air is more dense than hydrogen gas. E) For its molar mass, water has a high boiling point. Ans: E 4. Which of the following would you expect to have the highest boiling point? A) p 2 . B) ci~ C) Br2 · D) 1z E) All of the above have the same boiling point.

Ans: D 5. Whfch ·of the following is most likely to be a solid at room temperature? A) Na2S , B) HF C) NH3 D) N2 E) H20 . Ans: A

II. . g should have the lowest boiling point? 6. Which of the o owm A) Na2S B) HF C) NH:i D) N2 E) H20 . ·fi ·

Ans: ·D

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171

·n a substance, forces i · tennolecu1ar th 7. On a relative basi~, the weaker J::tion. , . _ A) the greaterits heat of vap~ behavior. · B) the more it deviates from ideal gas articular temperature_. · . C) the greater its vap~r pres~ure at a p ·. . D) the higher its meltmg pomt. E) none of the_se Ans· C · d. • , . . . i . the least hydrogen bon mg? . Id ou expect to show . . 8. Which of the species below wou Y E) all the same A) NH3 B) H20 C) HF D) CR! . . Ans: D . ttracted to each other by a combination of . 9. _The molecules in a sample of soh_d S02are a · A) London fo~ces and H-bon~g. B) H-bonding and ionic bonding. . . . C) covalent bonding and dipol~-dipo~e mte~ctions. D) London forces and dipole-dipole mteractions. E) none of these Ans: D JO. Which of the following is the correct order of boiling points for KN03, CH30H, C2H6, Ne? A) Ne < CH30H < C2H6 < KN03 B) KN03 < CH30H < C2H6 < Ne C) Ne < C2li6 < KN03 < CH30H Ans: D

D) E)

Ne< C2H6 < CH30H < ~'N0 3 C2H6 la

d

carbon and Silicone: ·Network At ,

·

om1c Solids

65 . .What is responsible· for Capilla A) B)

_surface tension cohesive forces adhesive forces

C) Ans: E

.

. ry action, a property ofliquids? D) viscosity E) two of these

66. When a nonpolar liquid dis la s . . this .behavior? · ~ Y a convex men~scus, which of the following explains A)

B) C) D) E)

It has a low. surface ten : d fi . sion, an therefore clings to the glass.

Th e co hes1ve orces are str h h . .· fi onge~ t an t e adhesive forces toward the glass. Th e adb es1ve orces toward th l . . . . ,· . e g ass are stronger than the cohesive forces. The hqmd s viscosity is low. none of these

Ans: B '

'

'

67. You are given the follo'"'.ing boilin~ point data: Which one of the below Ii-quids would you expect to have the highest vapor pressure at room temperature? . · A) . 100°c

B)

methanol, CH3OH

64.96°C

C) D) E)

ethanol, CH 3CH2OH diethyl ether, CH3OH2-0-CH2CH3

. ethylene glycol, HO-CH2-CHi-OH Ans: D · ·

78.5°C 34.5°C 198°C

68. Given below are the temperatures at which two different liquid compounds with the same empirical formula have a vapor pressure of 400 torr. 0 Compound T ( C) dimethyl ether, CH3-0-CH3 -~7.8 ethanol CH3CH2OH 63.5 Which of the following Statements (a-d) is false? . . A) Increasing the temperatu~e will increase the ~ap(l~r P:de)ssurthe of bohth l~qu(1 ~s. "d) 1 1 B) Intermolecular attractive forces are stronger m 1qm e ano t an m 1qm

' C)

dimethyl ether. . · . ·n b h· h h h Jb T The normal boiling poi~t of dimethyl ether w1 e rg er t an t e norma 01 mg 1

D) E)

of ethanol. · h · -· 400 t · h" h oint P orr ts 1g er · h t mperature at which t e vapor pressure ts th The reason. at t fie ed·methyl ether) is that there is strong hydrogen bonding in for ethanol (than or J . ethanol. · None of these is false.

Ans: C

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181

· tetrachloride at standard . .. oint of carbon 69. Given the graph below, what 1s the boibng P pressure? I

l ·-~

D) E)

A)

60°~C B) 34°C C) 98°C Ans: D

770c . . th t . .:: . graph does_not give a m1ormat!on

. . t ntil equilibrium is reached. At 70. A liquid placed in a closed contamer will evapo~ e u ? . h. h fth t through dis not true . ·1·1: . eqm 1unum, w_ 1c o e statemen s a cules is called the vapor pressure of 1 A) The partial pressure exerted by the-vapor mo e . the liquid. B) Liquid molecules are still evaporating. . · , _ C) .The number of vapor molecules remains essentially c?nstant. . D) The boundary (meniscus) between liquid and vapor disappears. E) All of these are true. Ans: D 71. Which best explains the following trend? Element b.p. (K) He 4 Ne 25 Ar 95 Kr 125 Xe 170 A) London dispersion forces B) dipole-dipole interaction C) hydrogen bonding

D) E)

Le Chatelier'~ principle none of these

Ans: A 72. In which of the following processes will energy be evol d h · . . ve as eat?

:j C)

~~!:i:;;~on vaporization

·

·

~j

meltin~ none o these

·

Ans: B 73. When one mole of benzene is vaporized at . ·1· · f353 aconstantpre b01 mg pomt o . .0 K, 30.57 kJ of energy (h . ssure of 1.00 atm and at its +28.90 L. What is ~E for this process? (I L- eat~ is absorbed and the volume change is A) 30.57 kJ B) 59.47 kJ C) 33.S0 kJ 101.3 J) 67 Ans: E l. kJ E) 27.64 kJ

~;m -

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Caroon .a uu ..-,rncone: Network At0 .

. m1c Solids

74. When one mole ofbenzen . . ·1· . e is vaponzed t . b 01 mg pomt of 353.0 K 30 kJ a a constant pressure of 1.00 atm.and at its 23

+28.90 L. What is LlH f~r th· of energy (heat) is absorbed and the volume change is 1 A) 27.30 kJ B) 33.1 6 kJ ?)rocess? (1 L-atrn == 101.3 J) 3 Ans: D 1.3 kJ D) 30.23 kJ E) 59.13 kJ

75. Which of the following is paired . · 1 A) crystalline solids-hi ·hi mcorrect y? B) amorphous solids g, ~dregular ~rrangement of their components · -consi erable disorder in their structures. C) umt cell-the ~mall est repeating unit of the lattice D) · gold metal-s1mple cubic unit ceU E) glass-am