Question 1

Which of the following molecules is polar?

Accepted Answer

A)   NBr3
B)   CH4
C)   CS2
D)   NH4+
E)   PCl5F) B) and E)
G) D) and E)

Question 2

Based on the Lewis structures, which of the following molecules would you expect to exhibit resonance?

Accepted Answer

A)   LiH
B)   CH4
C)   HNO2
D)   OF2
E)   none of theseF) B) and D)
G) C) and D)

Question 3

Given the bond enthalpies H-O (464) , Cl-Cl (243) , Cl-O (205) , and H-Cl (431)  in kJ/mol, compute ΔH° in kJ/mol for H2O(g)  + Cl2(g)  → HOCl(g)  + HCl(g) .

Accepted Answer

A)   -393
B)   -1100
C)   +71
D)   +393
E)   +1100F) C) and E)
G) A) and C)

Question 4

Which compound would be expected to have the shortest nitrogen-nitrogen bond?

Accepted Answer

A)   H2NNH2
B)   HNNH
C)   N2
D)   O2NNO2
E)   (CH3) 2NNH2F) A) and B)
G) None of the above

Question 5

What is the formal charge on P in PCl5?

Accepted Answer

A)   +5
B)   +2
C)   +1
D)   0
E)   -1F) A) and E)
G) A) and D)

Question 6

What is the formal charge on B in BF4-?

Accepted Answer

A)   +1
B)   -1
C)   +2
D)   0
E)   -2F) A) and E)
G) B) and E)

Question 7

Choose the INCORRECT statement.

Accepted Answer

A)   Molecules with unpaired electrons are paramagnetic.
B)   The bond order describes whether a covalent bond is single, double or triple.
C)   A larger bond order means a shorter bond length.
D)   Polar covalent bonds involve equal sharing of electrons in a bond.
E)   Bonds between like atoms share electrons equally.F) B) and C)
G) A) and C)

Question 8

In a Lewis structure, usually each atom acquires an outer-shell octet of electrons; H has 2 outer shell electrons.

Accepted Answer

A) True 
 B)False

Question 9

Given the following bond lengths in pm: N-N, 145; N=N, 123; Br-Br, 228 What is the best estimate of the N-Br bond length in NBr3 in pm?

Accepted Answer

A)   373 pm
B)   125 pm
C)   351 pm
D)   187 pm
E)   561 pmF) All of the above
G) C) and E)

Question 10

After drawing the Lewis dot structure for CH2O, determine the number of single bonds, double bonds, and lone pairs on the central atom.

Accepted Answer

A)   1, 2, 0
B)   2, 1, 1
C)   3, 0, 1
D)   3, 1, 0
E)   2, 1, 0F) A) and D)
G) A) and B)

Question 11

Arrange the following in order of increasing electronegativity: Cs, F, As, Cl.

Accepted Answer

A)   As 
B)   Cl 
C)   As 
D)   Cl 
E)   Cs < As < Cl < FF) A) and D)
G) All of the above

Question 12

Given the bond enthalpies C=C (611) , C≡C (837) , H-H (436) ,C-H (414)  all in kJ/mol, estimate ΔH for the following reaction: C2H2(g)  + H2(g)  → C2H4(g)

Accepted Answer

A)   -60 kJ
B)   -166 kJ
C)   -994 kJ
D)   +166 kJ
E)   98 kJF) A) and E)
G) None of the above

Question 13

How many bond pairs ("bp")  and how many lone pairs ("lp")  should be shown in the Lewis structure for carbon monoxide?

Accepted Answer

A)   1 bp/4 lp
B)   2 bp/3 lp
C)   3 bp/2 lp
D)   4 bp/1 lp
E)   5 bp/0 lpF) B) and D)
G) A) and C)

Question 14

Which of the following has a molecular structure that can be represented without use of an "expanded octet"?

Accepted Answer

A)   Fe(CN) 63-
B)   C2Cl6
C)   SF6
D)   PF5
E)   PtCl5-F) B) and E)
G) None of the above

Question 15

Which of the following bonds is probably the most polar?

Accepted Answer

A)   N-H in NH3
B)   O-H in H2O
C)   P-H in PH3
D)   Se-H in SeH2
E)   C-H in CH4F) B) and E)
G) B) and D)

Question 16

Write a Lewis structure for calcium hydride.

Accepted Answer

A)   
B)   
C)   
D)   H-Ca-H
E)   Ca-HF) D) and E)
G) C) and E)

Question 17

Which of the following would be properly classified as a set of covalent molecules?

Accepted Answer

A)   NaClO4, C4H10, NH3
B)   NaCl, CH4, S8
C)   CO2, HCN, O2
D)   CO2, NH4Cl, C2H6
E)   AgCl, ScF3, P4F) All of the above
G) None of the above

Question 18

Polar bonds are caused by the bonding pair of electrons being attracted more to one atom than the other.

Accepted Answer

A) True 
 B)False

Question 19

After drawing the Lewis dot structure for IF7, determine the number of single bonds, double bonds, and lone pairs on the central atom.

Accepted Answer

A)   3, 2, 1
B)   7, 0, 1
C)   7, 0, 0
D)   1, 0, 0
E)   4, 0, 0F) C) and D)
G) None of the above

Question 20

The electron-pair geometry of H2O is ________.

Accepted Answer

A)   tetrahedral
B)   linear
C)   trigonal planar
D)   bent
E)   V-shapedF) A) and B)
G) B) and D)

Exam 10: Chemical Bonding I: Basic Concepts

Given the following bond lengths in pm: N-N, 145; N=N, 123; Br-Br, 228 What is the best estimate of the N-Br bond length in NBr3 in pm?

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Based on the Lewis structures, which of the following molecules would you expect to exhibit resonance?

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In a Lewis structure, usually each atom acquires an outer-shell octet of electrons; H has 2 outer shell electrons.

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Write a Lewis structure for calcium hydride.

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What is the formal charge on P in PCl5?

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The electron-pair geometry of H2O is ________.

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Which of the following has a molecular structure that can be represented without use of an "expanded octet"?

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Choose the INCORRECT statement.

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What is the formal charge on B in BF4-?

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Which of the following bonds is probably the most polar?

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After drawing the Lewis dot structure for IF7, determine the number of single bonds, double bonds, and lone pairs on the central atom.

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After drawing the Lewis dot structure for CH2O, determine the number of single bonds, double bonds, and lone pairs on the central atom.

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Polar bonds are caused by the bonding pair of electrons being attracted more to one atom than the other.

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Given the bond enthalpies C=C (611) , C≡C (837) , H-H (436) ,C-H (414) all in kJ/mol, estimate ΔH for the following reaction: C2H2(g) + H2(g) → C2H4(g)

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Arrange the following in order of increasing electronegativity: Cs, F, As, Cl.

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Which of the following molecules is polar?

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Which of the following would be properly classified as a set of covalent molecules?

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Which compound would be expected to have the shortest nitrogen-nitrogen bond?

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Given the bond enthalpies H-O (464) , Cl-Cl (243) , Cl-O (205) , and H-Cl (431) in kJ/mol, compute ΔH° in kJ/mol for H2O(g) + Cl2(g) → HOCl(g) + HCl(g) .

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How many bond pairs ("bp") and how many lone pairs ("lp") should be shown in the Lewis structure for carbon monoxide?

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Given the following bond lengths in pm: N-N, 145; N=N, 123; Br-Br, 228 What is the best estimate of the N-Br bond length in NBr₃ in pm?

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The electron-pair geometry of H₂O is ________.

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After drawing the Lewis dot structure for CH₂O, determine the number of single bonds, double bonds, and lone pairs on the central atom.

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Given the bond enthalpies C=C (611) , C≡C (837) , H-H (436) ,C-H (414) all in kJ/mol, estimate ΔH for the following reaction: C₂H₂(g) + H₂(g) → C₂H₄(g)

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Given the bond enthalpies H-O (464) , Cl-Cl (243) , Cl-O (205) , and H-Cl (431) in kJ/mol, compute ΔH° in kJ/mol for H₂O(g) + Cl₂(g) → HOCl(g) + HCl(g) .

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