1. Which of the following pairs of atoms are least likely to form an ionic compound?
   1. Ni, O
   2. Na, F
   3. Cu, Cl
   4. Li, Mg
   5. Li, F

2. The bond in dinitrogen (N₂) is a:
   1. double bond.
   2. single bond.
   3. triple bond.
   4. lone pair.
   5. none of the above

3. Which of the following formulas are incorrect on the basis of simple Lewis dot structures?
   1. LiCl
   2. MgO
   3. Na₂O
   4. CO₂
   5. none of these

4. Which of the following bonds is most polar?
   1. H-F
   2. H-Cl
   3. H-H
   4. F-F
   5. H-I

5. What type of hybrid orbital is present in methane (CH₄)?
   1. sp²
   2. sp³
   3. sp³d
   4. sp
   5. sp³d²

6. Which of the following molecules requires two resonance hybrid Lewis structures to account for the bonding?
   1. SO₂
   2. CO₂
   3. O₂
   4. CH₄
   5. C₂H₄

7. The formal oxidation number of nitrogen in ammonia is:
   1. +3
   2. -1
   3. -4
   4. +1
   5. -3

8. The Lewis structure for CO₂ is:
   

9. Which of the following pairs of atoms are most likely to form a covalent compound?
   1. Ni, O
   2. Na, F
   3. Cu, Cl
   4. C, O
   5. Li, F

10. The number of valence shell electrons in chlorine is:
    1. 17
    2. 2
    3. 5
    4. 7
    5. 4

11. The bond in oxygen (O₂) is a:
    1. double bond.
    2. single bond.
    3. triple bond.
    4. lone pair.
    5. none of the above

12. Which of the following oxides is ionic?
    1. XeO₃
    2. Y₂O₃
    3. SO₂
    4. N₂O
    5. P₂O₅

13. What is the formal charge on carbon in the preferred structure of CO₂?
    1. 0
    2. -1
    3. +2
    4. -3
    5. +4

14. What is the oxidation number of I in NaIO₃?
    1. -1
    2. +6
    3. +5
    4. +4
    5. -2

15. Given the following table of bond enthalpies:

    average bond	bond enthalpy (kJ/mol)
    C-H	413
    C-C	348
    C-N	293
    N-H	391
    H-H	436
    N-N	163
    O-H	463
    C=C	614
    C-N (triple bond)	891

    Calculate the H for the following reaction in the gas phase:

    HCN(g) + 2H₂(g) --> CH₃NH₂(g)
    1. -736 kJ
    2. -551 kJ
    3. -138 kJ
    4. +230 kJ
    5. +275 kJ

16. Which of the following IIIA family members should form the fluoride molecule with the highest lattice energy?
    1. AlF₃
    2. GaF₃
    3. InF₃
    4. TlF₃
    5. TlF

17. In which of the following molecules are the bonds most polar?
    1. H₂
    2. HF
    3. CH₄
    4. NH₃
    5. H₂O

18. Which of the pattern does not obey the octet rule?
    

19. Which of the following Lewis structures is least plausible?
    

20. The total number of electron pairs in the valence shell of Se in an SeF₄ molecule is:
    1. 4 pairs, all bonding.
    2. 5 pairs, 4 bonding and 1 non-bonding.
    3. 6 pairs, 4 bonding and 2 non-bonding.
    4. 8 pairs, 4 bonding and 4 non-bonding.
    5. 17 pairs, 4 bonding and 13 non-bonding.

21. Which of the following could be the atom X in the following neutral (uncharged) molecule?
    
    1. H
    2. F
    3. C
    4. N
    5. O

22. The number of bonding electron pairs in the best Lewis structure of CS₂ is:
    1. 1
    2. 2
    3. 3
    4. 4
    5. 5

23. The number of equivalent resonance structures connected with the best Lewis structure of SO₃ is:
    1. 0
    2. 1
    3. 2
    4. 3
    5. 4

24. Atom X in the structure below is most likely:
    
    1. Cl
    2. S
    3. P
    4. Si
    5. Al

25. The symbols and respective electronegativities for elements in a hypothetical universe are given in the table below:

    element	electronegativities
    L	2.0
    M	3.5
    Q	0.9
    R	2.5

    Which of the following bonds is least polar (i.e. most nonpolar)?

    1. L-R
    2. M-L
    3. Q-M
    4. R-Q
    5. M-R

26. Which molecule has one pair of nonbonding electrons on the central atom?
    1. PCl₃
    2. CO₂
    3. SO₃
    4. BF₃
    5. SF₂

27. What is the oxidation number and formal charge of iodine in the IF₄⁺ ion?

    	oxidation state (number)	formal charge
    (a)	-1	-1
    (b)	+1	+5
    (c)	+3	0
    (d)	+5	+1
    (e)	+5	+5

28. Given the following table of bond energies, determine H for the reaction,
    CO(g) + 2H₂(g) --> CH₃OH(g)

    bond	energy (kJ/mol)
    C-O	358
    C=O	799
    C-O (triple bond)	1072
    H-H	436
    C-H	413
    O-H	463

    1. -830 kJ
    2. -557 kJ
    3. -552 kJ
    4. -389 kJ
    5. -116 kJ

29. Which of the following is the best electron-dot description for sulfur dioxide, SO₂?
    

30. Hydrogen reacts with both active metals and nonmetals, e.g.
    (1) H₂(g) + 2Na(s) --> 2NaH(s)
    (2) H₂(g) + Cl₂(g) --> 2HCl(g)

    Consider the following statements pointing out possible similarities between these two reactions:

    1. The products of the two reactions are covalent molecules.
    2. The products of the two reactions are ionic species.
    3. Both reactions involve oxidation-reduction.
    4. The oxidation number of hydrogen decreases in reaction (1) and increases in reaction (2).

    Which of these are correct?

    1. 1, 3 and 4
    2. 2, 3 and 4
    3. 1 and 3
    4. 3 and 4
    5. only 3

31. Which of the following compounds has the largest lattice energy in the crystal state?
    1. LiCl
    2. NaBr
    3. MgI₂
    4. CaO
    5. There is not enough information to answer this question.

32. The crystal lattice energy can be determined by means of a Born-Haber cycle, in which several reactions are combined according to Hess' Law. In applying this procedure to the lattice energy of KBr, the following reactions are combined:

    (1)	K(s) --> K(g)
    (2)	1/2Br2(l) --> Br(g)
    (3)	K(g) --> K+(g) + e-
    (4)	Br(g) + e- --> Br-(g)
    (5)	K(s) + 1/2Br2(l) --> KBr(s)

    For which of the above reactions is H (or E) < 0?

    1. All 5 reactions have H < 0
    2. Reactions 2, 4 and 5
    3. Reactions 4 and 5
    4. Reactions 2 and 4
    5. Only reaction 4

33. Which of the following will have the largest dipole moment?
    1. HF
    2. HCl
    3. HBr
    4. HI
    5. F₂

34. CO₂ is a nonpolar molecular (µ=0) whereas SO₂ is polar (µ=1.62 D). This difference is due to the fact that:
    1. C and O have approximately the same electronegativity while S and O have different electronegativities.
    2. CO₂ has an even number of double bonds whereas SO₂ has an odd number of double bonds.
    3. C and O are in different groups whereas S and O are in the same group.
    4. the C-O bond is nonpolar while the S-O bond is polar.
    5. CO₂ is linear whereas SO₂ is not linear.

35. Which of the following molecules contains a covalent triple bond?
    1. CO₂
    2. SO₃
    3. I₂
    4. NH₃
    5. N₂

36. How many non-bonding electrons are located on the central atom of ICl₄^-?
    1. 0
    2. 1
    3. 2
    4. 4
    5. 6

37. The bonds in carbon dioxide are
    1. single bonds
    2. ionic bonds
    3. triple bonds
    4. double bonds
    5. none of these

38. The octet rule does not apply to
    1. F
    2. O
    3. Cl
    4. N
    5. H

39. Which of the following bonds has the largest dipole moment?
    1. Cl-Cl
    2. Cl-Br
    3. H-F
    4. H-I

40. Which of the following is a non-polar covalent compound?
    1. CH₄
    2. HCN
    3. CH₃CN
    4. HCl
    5. NaCl

41. How many valence electrons does a nitrogen atom possess?
    1. 3
    2. 4
    3. 5
    4. 6
    5. 0

42. The oxidation number of sulfur in SF₆ is
    1. +1
    2. -2
    3. -1
    4. +6
    5. 0

43. What is the state of hybridization of the carbon atoms in ethylene, C₂H₄?
    1. sp²
    2. sp
    3. sp³
    4. sp³d²
    5. none of these

44. Which one of the following statements is incorrect?
    1. The electrons involved in pi bonding are more delocalized in benzene than in ethylene.
    2. The bond order of the carbon - carbon bond in ethane, C₂H₆ , is two.
    3. Pi orbitals involve the overlap of un-hybridized p atomic orbitals.
    4. 2s atomic orbitals tend to be lower in energy than 2p orbitals.

45. The type(s) of bonding present in a sample of sodium nitrate, NaNO₃, are:
    1. covalent bonds only.
    2. ionic bonds only.
    3. metallic bonds only.
    4. covalent and ionic bonds.
    5. ionic and metallic bonds.

46. Which of the following species is best described by a Lewis structure involving resonance?
    1. CO₃^2-
    2. PO₄^3-
    3. HSO₄^- (H bonded to O)
    4. All of the above are best described by resonance.
    5. None of (a)-(c).

47. Which of the following molecules has a non-zero dipole moment?
    1. Cl₂O
    2. I₂
    3. BF₃
    4. CO₂
    5. SF₆

48. How many lone (unshared) pairs are there in the best Lewis structure of ClF₃?
    1. 11
    2. 10
    3. 9
    4. 8
    5. 7

49. Which of the following compounds (or ions) contains an atom that does NOT follow the octet rule?
    1. BrF₃
    2. CBr₄
    3. NO⁺
    4. BF₄^-
    5. NCl₃

50. What is atom X in the Lewis structure of the following dianion?
    
    1. Xe
    2. Cl
    3. S
    4. N
    5. C

51. How many electron pairs are there in the Lewis structure of SF₆? Include all shared pairs and all unshared pairs.
    1. 8
    2. 16
    3. 24
    4. 48
    5. 56

52. Which of the following elements forms bonds with fluorine that are the most covalent?
    1. Al
    2. Ca
    3. O
    4. P
    5. Se

53. Which of the following ionic compounds has the largest lattice energy?
    1. NaCl
    2. NaI
    3. KI
    4. MgO
    5. MgS

54. Which of the following substances is expected to involve the most ionic bonding?
    1. LiF
    2. LiCl
    3. CH₄
    4. Cl₂
    5. PF₆

55. The oxidation number of carbon in carbon monoxide (CO) is:
    1. +4
    2. -2
    3. +1
    4. +2
    5. none of these

56. orbital overlap involves:
    1. "end-on" bonding with s orbitals.
    2. "sideways" approach of pairs of p orbitals.
    3. overlap of an s with a p orbital.
    4. production of a bonding but not an antibonding orbital.
    5. None of the above.

57. Given that the electron configuration of carbon is [He]2s²2p² and chlorine is [Ne]3s²3p⁵, how many lone pairs are on the C atom in CHCl₃?
    1. 0
    2. 4
    3. 2
    4. 1
    5. 6

58. Given the electronic configuration of sulfur is [Ne]3s²3p⁴, the hybrid orbital involved in bonding in SF₆ is:
    1. sp³
    2. sp²
    3. sp²d²
    4. sp³d⁵
    5. sp³d²

59. The C=C double bond in ethene (or ethylene), C₂H₄, is composed of:
    1. two bonds.
    2. 3p³ hybridization.
    3. two sigma bonds.
    4. one bond + one sigma bond.
    5. only unhybridized p orbitals.

60. Which of the following statements are true?
    1. The number of MO's in a molecule equals twice the number of constituent atomic orbitals.
    2. As bonding MO's become more stable, antibonding MO's become equally less stable.
    3. In MO's, the number of bonding electrons equals the number of antibonding electrons.
    4. Each bonding MO can accomodate only one electron.
    5. None of the above.

61. What is the hybridization of phosphorus in PF₅?
    1. sp
    2. sp²
    3. sp³
    4. sp³d
    5. sp³d²

62. Indicate the number and kinds of bonds present in HCN.
    1. 1 sigma and 1
    2. 1 sigma and 2
    3. 1 sigma and 3
    4. 2 sigma and 1
    5. 2 sigma and 2

63. According to the valence-bond theory, which two orbitals overlap to form the covalent bond in H-Cl?
    1. s, s
    2. s, p
    3. s, d
    4. s, d_z
    5. none of the above

64. What is the hybrid orbital diagram for boron in BF₃?
    

65. Given the following table of bond enthalpies:

    average bond	bond enthalpy (kJ/mol)
    O-H	463
    H-H	436
    C-H	413
    N-N	163
    O-N	201
    N-H	391
    C-C	348
    N=N	418
    C-N (triple bond)	891

    Calculate the H for the following reaction in the gas phase.

    
    1. -30. kJ
    2. +289 kJ
    3. -289 kJ
    4. +493 kJ
    5. -493 kJ

Answers

1. D
2. C
3. E
4. A
5. B
6. A
7. E
8. A
9. D
10. D
11. A
12. B
13. A
14. C
15. C
16. A
17. B
18. C
19. A
20. B
21. E
22. D
23. D
24. B
25. A
26. A
27. D
28. E
29. B
30. D
31. D
32. C
33. A
34. E
35. E
36. D
37. D
38. E
39. C
40. A
41. C
42. D
43. A
44. B
45. D
46. A
47. A
48. A
49. A
50. C
51. C
52. C
53. D
54. A
55. D
56. B
57. A
58. E
59. D
60. B
61. D
62. E
63. B
64. E
65. E