Question 1

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 CH4

Question 2

What is the formal charge on B in BF4-?

Accepted Answer

A)   +1
B)   -1
C)   +2
D)   0
E)   -2

Question 3

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 kJ

Question 4

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 pm

Question 5

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 < F

Question 6

What is the formal charge on P in PCl5?

Accepted Answer

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

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.

Question 8

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 lp

Question 9

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 these

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, 0

Question 11

The electron-pair geometry of H2O is ________.

Accepted Answer

A)   tetrahedral
B)   linear
C)   trigonal planar
D)   bent
E)   V-shaped

Question 12

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, 0

Question 13

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

Accepted Answer

A)   H2NNH2
B)   HNNH
C)   N2
D)   O2NNO2
E)   (CH3) 2NNH2

Question 14

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, P4

Question 15

Write a Lewis structure for calcium hydride.

Accepted Answer

A)   
B)   
C)   
D)   H-Ca-H
E)   Ca-H

Question 16

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 17

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 18

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-

Question 19

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)   +1100

Question 20

Which of the following molecules is polar?

Accepted Answer

A)   NBr3
B)   CH4
C)   CS2
D)   NH4+
E)   PCl5

Exam 10: Chemical Bonding I: Basic Concepts

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

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

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Which of the following bonds is probably the most polar?

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

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

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What is the formal charge on B in BF4-?

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

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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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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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The electron-pair geometry of H2O is ________.

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What is the formal charge on P in PCl5?

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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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Write a Lewis structure for calcium hydride.

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Which of the following molecules is polar?

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Choose the INCORRECT statement.

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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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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 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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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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The electron-pair geometry of H₂O is ________.

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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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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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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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