Chemistry Principles and Reactions

William L. Masterton, Cecile N. Hurley

Chapter 7

Covalent Bonding - all with Video Answers

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Chapter Questions

Problem 1

Write the Lewis structures for the following molecules and polyatomic ions. In each case, the first atom is the central atom.
(a) CCla
(b) $\mathrm{NCl}_{3}$
(c) $\mathrm{COCl}_{2}$
(d) $\mathrm{SO}_{3}^{2-}$

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Problem 2

Follow the directions of Question 1 for
(a) $\mathrm{NH}_{3}$
(b) $\mathrm{KrF}_{2}$
(c) $\mathrm{NO}^{+}$
(d) $\mathrm{BrO}_{2}^{-}$

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Problem 3

Follow the directions of Question 1 for
(a) $\mathrm{IO}_{2}^{-}$
(b) $\mathrm{SiF}_{4}$
(c) $\mathrm{BrI}_{3}$
(d) $\mathrm{CN}^{-}$

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Problem 4

Follow the directions of Question 1 for
(a) $\mathrm{ClF}_{4}^{-}$
(b) $\mathrm{PF}_{6}{ }^{-}$
(c) CNS
(d) $\mathrm{SnCl}_{5}^{-}$

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Problem 5

Follow the directions of Question 1 for
(a) $\mathrm{OCl}_{2}$
(b) $\mathrm{PF}_{3}$
(c) $\mathrm{SbCl}_{6}^{-}$
(d) $\mathrm{ICl}_{4}^{-}$

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Problem 6

Follow the directions of Question 1 for
(a) $\mathrm{C}_{2}^{2-}$
(b) NFO
(c) $\mathrm{BrF}_{4}^{+}$
(d) $\mathrm{NI}_{3}$

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Problem 7

Oxalic acid, $\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4},$ is a poisonous compound found in rhubarb leaves. Draw the Lewis structure for oxalic acid. There is a single bond between the two carbon atoms, each hydrogen atom is bonded to an oxygen atom, and each carbon is bonded to two oxygen atoms.

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Problem 8

Radio astronomers have detected the isoformyl ion, $\mathrm{HOC}^{+},$ in outer space. Write the Lewis structure for this ion.

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Problem 9

Draw Lewis structures for the following species. (The skeleton is indicated by the way the molecule is written.)

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Problem 10

Follow the directions of Question 9 for the following species:

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Problem 11

Dinitrogen pentoxide, $\mathrm{N}_{2} \mathrm{O}_{5},$ when bubbled into water can form nitric acid. Its skeleton structure has no $\mathrm{N}-\mathrm{N}$ or $\mathrm{O}-\mathrm{O}$ bonds. Write its Lewis structure.

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Problem 12

Formic acid is the irritating substance that gets on your skin when an ant bites. Its formula is HCOOH. Carbon is the central atom, and it has no $\mathrm{O}-\mathrm{O}$ bonds. Draw its Lewis structure.

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Problem 13

Two different molecules have the formula $\mathrm{C}_{2} \mathrm{H}_{2} \mathrm{Cl}_{2}$. Draw a Lewis structure for each molecule. (All the $\mathrm{H}$ and $\mathrm{Cl}$ atoms are bonded to carbon. The two carbon atoms are bonded to each other.)

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Problem 14

Two different molecules have the formula $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O} .$ One of the molecules has the oxygen atom bonded to both carbon atoms. The other molecule has the oxygen atom bonded to only one carbon atom while both carbon atoms are bonded to each other. Write Lewis structures for both of these compounds.

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Problem 15

Give the formula of a polyatomic ion that you would expect to have the same Lewis structure as
(a) $\mathrm{Cl}_{2}$
(b) $\mathrm{H}_{2} \mathrm{SO}_{4}$
(c) $\mathrm{CH}_{4}$
(d) $\mathrm{GeCl}_{4}$

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Problem 16

Give the formula for a molecule that you would expect to have the same Lewis structure as
(a) $\mathrm{BrO}^{-}$
(b) $\mathrm{NH}_{4}+$
(c) $\mathrm{CN}^{-}$
(d) $\mathrm{SO}_{4}^{2-}$

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Problem 17

Write a Lewis structure for
(a) $\mathrm{XeF}_{3}{ }^{+}$
(b) $\mathrm{PCl}_{4}^{+}$
(c) $\mathrm{BrF}_{5}$
(d) $\mathrm{HPO}_{4}^{2-}($ no $\mathrm{P}-\mathrm{H}$ or $\mathrm{O}-\mathrm{O}$ bonds $)$

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Problem 18

Write a Lewis structure for
(a) $\mathrm{BCl}_{4}$
(b) $\mathrm{ClO}^{-}$
(c) $\mathrm{S}_{2} \mathrm{O}_{3}{ }^{2-}$
(d) $\mathrm{NFCl}_{2}$

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Problem 19

Write reasonable Lewis structures for the following species, none of which follow the octet rule.
(a) $\mathrm{BF}_{3}$
(b) $\mathrm{NO}$
(c) $\mathrm{CO}^{+}$
(d) $\mathrm{ClO}_{3}$

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Problem 20

Write reasonable Lewis structures for the following species, none of which follow the octet rule.
(a) $\mathrm{BeCl}_{2}$
(b) $\mathrm{SeO}_{2}^{-}$
(c) $\mathrm{ClO}_{3}$
(d) $\mathrm{CH}_{3}$

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Problem 21

Draw possible resonance structures for
(a) $\mathrm{Cl}-\mathrm{NO}_{2}$
(b) $\mathrm{H}_{2} \mathrm{C}-\mathrm{N}-\mathrm{N}$
(c) $\mathrm{SO}_{3}$

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Problem 22

Draw resonance structures for
(a) $\mathrm{SeO}_{3}$
(b) $\mathrm{CS}_{3}{ }^{2-}$
(c) CNO $^{-}$

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Problem 23

The Lewis structure for hydrazoic acid may be written as
$$ \stackrel{\mathrm{H}}{\mathrm{N}}=\mathrm{N}=\ddot{\mathrm{N}} $$

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Problem 24

The oxalate ion, $\mathrm{C}_{2} \mathrm{O}_{4}^{2-},$ has the skeleton structure <smiles>O=CC(O)C(=O)O</smiles>
(a) Complete the Lewis structure of this ion.
(b) Draw three possible resonance forms for $\mathrm{C}_{2} \mathrm{O}_{4}^{2-}$, equivalent to the Lewis structure drawn in (a).
(c) Is
<smiles>CCOC(=O)OCC</smiles>

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Problem 25

The skeleton structure for disulfur dinitride, $\mathrm{S}_{2} \mathrm{~N}_{2}$, is Draw possible resonance forms of this molecule.

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Problem 26

Borazine, $\mathrm{B}_{3} \mathrm{~N}_{3} \mathrm{H}_{6},$ has the skeleton Draw the resonance forms of the molecule.

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Problem 27

What is the formal charge on the indicated atom in each of the following species?
(a) sulfur in $\mathrm{SO}_{2}$
(b) nitrogen in $\mathrm{N}_{2} \mathrm{H}_{4}$

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Problem 28

Follow the directions in Question 27 for
(a) oxygen in HOF
(b) nitrogen in $\mathrm{NO}_{2}$ -
(c) phosphorus in $\mathrm{PCl}_{1}$

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Problem 29

Below are two different Lewis structures tor nitrous acra $\left(\mathrm{HNO}_{2}\right) .$ Which is the better Lewis structure based only on formal charge?

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Problem 30

Below are two different Lewis structures for the thiosulfate ion $\left(\mathrm{S}_{2} \mathrm{O}_{3}^{2-}\right) .$ Which is the better Lewis structure based only on formal charge?

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Problem 31

Predict the geometry of the following species:
(a) $\mathrm{SO}_{2}$
(b) $\mathrm{BeF}_{2}$
(c) $\mathrm{SeCl}_{4}$
(d) $\mathrm{PCl}_{5}$

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Problem 32

Predict the geometry of the following species:
(a) $\mathrm{O}_{3}$
(b) $\mathrm{OCl}_{2}$
(c) $\mathrm{SnCl}_{3}^{-}$
(d) $\mathrm{CS}_{2}$

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Problem 33

Predict the geometry of the following species:
(a) $\mathrm{SeOF}_{2}$
(b) $\mathrm{TeF}_{5}$
(c) $\mathrm{ICl}_{4}^{-}$
(d) $\mathrm{RnF}_{2}$

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Problem 34

Predict the geometry of the following species:
(a) NNO
(b) $\mathrm{ONCl}$
(c) $\mathrm{NH}_{4}{ }^{+}$
(d) $\mathrm{O}_{3}$

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Problem 35

Predict the geometry of the following species:
(a) $\mathrm{ClF}_{2}^{-}$
(b) $\mathrm{SeF}_{5} \mathrm{Br}$
(c) $\mathrm{SO}_{3}^{2-}$
(d) $\mathrm{BrO}_{2}^{-}$

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Problem 36

Predict the geometry of the following species:
(a) $\mathrm{ClF}_{5}$
(b) $\mathrm{XeF}_{4}$
(c) $\mathrm{SiF}_{6}^{2-}$
(d) $\mathrm{PCl}_{5}$

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Problem 37

Give all the ideal bond angles $\left(109.5^{\circ}, 120^{\circ},\right.$ or $\left.180^{\circ}\right)$ in the following molecules and ions. (The skeleton does not imply geometry.)
(a) $\mathrm{Cl}-\mathrm{S}-\mathrm{Cl}$
(b) $\mathrm{F}-\mathrm{Xe}-\mathrm{F}$
(c) <smiles>CC(O)CN</smiles>
(d) <smiles>C=CCC#N</smiles>

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Problem 38

Follow the instructions in Question 37 for
(a) $\mathrm{NO}_{2}^{-}$
(b) $\mathrm{BF}_{3}$
(c)<smiles>O=[N+]([O-])O</smiles>
(d) <smiles>CNN</smiles>

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Problem 39

Peroxypropionyl nitrate (PPN) is an eye irritant found in smog. Its skeleton structure is
<smiles>CC(C)(C)OCON(O)O</smiles>
(a) Draw the Lewis structure of PPN.
(b) Indicate all the bond angles.

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Problem 40

An objectionable component of smog is acetyl peroxide, which has the following skeleton structure.
<smiles>CC(=O)OCC(C)O</smiles>
(a) Draw the Lewis structure of this compound.
(b) Write the bond angles indicated by the numbered angles.

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Problem 41

The uracil molecule is one of the bases in DNA. Estimate the approximate values of the indicated bond angles. Its skeleton (not its Lewis structure) is given below.

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Problem 42

Niacin is one of the B vitamins $\left(\mathrm{B}_{3}\right)$. Estimate the approximate values of the indicated bond angles. Its skeleton (not its Lewis structure) is given below.

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Problem 43

Which of the species with octets in Question 31 are dipoles?

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Problem 44

Which of the species with octets in Question 32 are dipoles?

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Problem 45

Which of the species with octets in Question 33 are dipoles?

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Problem 46

Which of the species with octets in Question 34 are dipoles?

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Problem 47

47. There are three compounds with the formula $\mathrm{C}_{2} \mathrm{H}_{2} \mathrm{Cl}_{2}$ : Which of these molecules are polar?

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Problem 48

There are two different molecules with the formula $\mathrm{N}_{2} \mathrm{~F}_{2}$ Is either molecule polar? Explain.

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Problem 49

Give the hybridization of the central atom in each species in Question 31 .

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Problem 50

. Give the hybridization of the central atom in each species in Question 32 .

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Problem 51

Give the hybridization of the central atom in each species in Question $33 .$

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Problem 52

Give the hybridization of the central atom in each species in Question 34

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Problem 53

Give the hybridization of the central atom in each species in Question 35 .

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Problem 54

Give the hybridization of the central atom in each species in Question $36 .$

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Problem 55

In each of the following polyatomic ions, the central atom has an expanded octet. Determine the number of electron pairs around the central atom and the hybridization in
(a) $\mathrm{SF}_{2}^{2-}$
(b) $\mathrm{AsCl}_{6}^{-}$
(c) $\mathrm{SCl}_{4}^{2-}$

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Problem 56

Follow the directions of Question 55 for the following polyatomic ions.
(a) $\mathrm{ClF}_{4}-$
(b) $\mathrm{GeCl}_{6}^{2-}$
(c) $\mathrm{SbCl}_{4}^{-}$

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Problem 57

Give the hybridization of each atom (except $\mathrm{H}$ ) in the solvent dimethylsulfoxide. (Unshared electron pairs are not shown.)

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Problem 58

Acrylonitrile, $\mathrm{C}_{3} \mathrm{H}_{3} \mathrm{~N}$, is the building block of the polymer Orlon. Its Lewis structure is What is the hybridization of nitrogen and of the three numbered carbon atoms?

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Problem 59

What is the hybridization of nitrogen in

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Problem 60

What is the hybridization of carbon in

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Problem 61

Give the hybridization of the central atom (underlined in red).
(a) $\mathrm{COCl}_{2}$
(b) HNO $_{2}$
(c) $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCH}_{3}$

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Problem 62

Give the hybridization of the central atom (underlined in red).
(a) $\mathrm{HOBrO}_{3}$
(b) $\mathrm{Cl}_{2} \mathrm{O}$
(c) $\mathrm{OPBr}_{3}$

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Problem 63

Give the number of sigma and pi bonds in the molecule in Question 57

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Problem 64

Give the number of sigma and pi bonds in the molecule in Question 58 .

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Problem 65

Give the number of sigma and pi bonds in each species in Ouestion 59

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Problem 66

Give the number of sigma and pi bonds in each species in Question $60 .$

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Problem 67

In which of the following molecules does the sulfur have an expanded octet? For those that do, write the Lewis structure.
(a) $\mathrm{SO}_{2}$
(b) $\mathrm{SF}_{4}$
(c) $\mathrm{SO}_{2} \mathrm{Cl}_{2}$
(d) $\mathrm{SF}_{6}$

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Problem 68

Consider the pyrosulfate ion, $\mathrm{S}_{2} \mathrm{O}_{7}^{2-}$. It has no sulfursulfur nor oxygen-oxygen bonds.
(a) Write a Lewis structure for the pyrosulfate ion using only single bonds.
(b) What is the formal charge on the sulfur atoms for the Lewis structure you drew in part (a)?
(c) Write another Lewis structure using six $\mathrm{S}=\mathrm{O}$ bonds and two $\mathrm{O}-\mathrm{S}$ bonds.
(d) What is the formal charge on each atom for the structure you drew in part (c)?

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Problem 69

Consider acetyl salicylic acid, better known as aspirin. Its structure is (a) How many sigma and pi bonds are there in aspirin?
(b) What are the approximate values of the angles marked (in blue) $\mathrm{A}, \mathrm{B},$ and $\mathrm{C} ?$
(c) What is the hybridization of each atom marked (in red) $1,2,$ and $3 ?$

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Problem 70

Complete the table on next page.

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Problem 71

. Given the following electronegativities $$ \begin{array}{lll} \mathrm{C} & =2.5 & \mathrm{~N}=3.0 & \mathrm{~S}=2.6 \end{array} $$ what is the central atom in CNS-?

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Problem 72

Based on the concept of formal charge, what is the central atom in
(a) HCN (do not include $\mathrm{H}$ as a possibility)?
(b) $\mathrm{NOCl}$ (Cl is always a terminal atom)?

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Problem 73

Describe the geometry of the species in which there are, around the central atom,
(a) four single bonds, two unshared pairs of electrons.
(b) five single bonds.
(c) two single bonds, one unshared pair of electrons.
(d) three single bonds, two unshared pairs of electrons.
(e) two single bonds, two unshared pairs of electrons.
(f) five single bonds, one unshared pair of electrons.

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Problem 74

Consider the following molecules: $\mathrm{SiH}_{4}, \mathrm{PH}_{3}, \mathrm{H}_{2} \mathrm{~S} . \mathrm{In}$
each case, a central atom is surrounded by four electron pairs. In which of these molecules would you expect the bond angle to be less than $109.5^{\circ}$ ? Explain your reasoning.

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Problem 75

Give the formula of an ion or molecule in which an atom of
(a) $\mathrm{N}$ forms three bonds using sp $^{3}$ hybrid orbitals.
(b) $\mathrm{N}$ forms two pi bonds and one sigma bond.
(c) $\mathrm{O}$ forms one sigma and one pi bond.
(d) $C$ forms four bonds in three of which it uses $s p^{2}$ hybrid orbitals.
(e) Xe forms two bonds using $s p^{3} \mathrm{~d}^{2}$ hybrid orbitals.

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Problem 76

In each of the following molecules, a central atom is surrounded by a total of three atoms or unshared electron pairs:
$\mathrm{SnCl}_{2}, \mathrm{BCl}_{3}, \mathrm{SO}_{2} .$ In which of these molecules would you expect the bond angle to be less than $120^{\circ}$ ? Explain your reasoning.

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Problem 77

Explain the meaning of the following terms.
(a) expanded octet
(b) resonance
(c) unshared electron pair
(d) odd-electron species

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Problem 78

A compound of chlorine and fluorine, CIF $_{x}$, reacts at about $75^{\circ} \mathrm{C}$ with uranium to produce uranium hexafluoride and chlorine fluoride, ClF. A certain amount of uranium produced $5.63 \mathrm{~g}$ of uranium hexafluoride and $457 \mathrm{~mL}$ of chlorine fluoride at $75^{\circ} \mathrm{C}$ and $3.00 \mathrm{~atm} .$ What is $x ?$ Describe the geometry, polarity, and bond angles of the compound and the hybridization of chlorine. How many sigma and pi bonds are there?

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Problem 79

Draw the Lewis structure and describe the geometry of the hydrazine molecule, $\mathrm{N}_{2} \mathrm{H}_{4} .$ Would you expect this molecule to be polar?

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Problem 80

Consider the polyatomic ion IO $_{6}^{5-}$. How many pairs of electrons are around the central iodine atom? What is its hybridization? Describe the geometry of the ion.

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Problem 81

It is possible to write a simple Lewis structure for the $\mathrm{SO}_{4}^{2-}$ ion, involving only single bonds, which follows the octet rule. However, Linus Pauling and others have suggested an alternative structure, involving double bonds, in which the sulfur atom is surrounded by six electron pairs.
(a) Draw the two Lewis structures.
(b) What geometries are predicted for the two structures?
(c) What is the hybridization of sulfur in each case?
(d) What are the formal charges of the atoms in the two structures?

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Problem 82

Phosphoryl chloride, $\mathrm{POCl}_{3}$, has the skeleton structure
Write (a) a Lewis structure for $\mathrm{POCl}_{3}$ following the octet rule. Calculate the formal charges in this structure. (b) a Lewis structure in which all the formal charges are zero. (The octet rule need not be followed.)

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