Chemistry

Steven S. Zumdahl, Susan A. Zumdahl

Chapter 8

Bonding: General Concepts - all with Video Answers

Educators

Chapter Questions

Problem 1

Explain the electronegativity trends across a row and down a column of the periodic table. Compare these trends with those of ionization energies and atomic radii. How are they related?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 2

The ionic compound $\mathrm{AB}$ is formed. The charges on the ions may be $+1,-1 ;+2,-2 ;+3,-3 ;$ or even larger. What are the factors that determine the charge for an ion in an ionic compound?

LJ

Lena Jake

Numerade Educator

Problem 3

Using only the periodic table, predict the most stable ion for $\mathrm{Na}$, $\mathrm{Mg}, \mathrm{Al}, \mathrm{S}, \mathrm{Cl}, \mathrm{K}, \mathrm{Ca}$, and $\mathrm{Ga}$. Arrange these from largest to smallest radius, and explain why the radius varies as it does. Compare your predictions with Fig. $8.8$.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 4

The bond energy for a $\mathrm{C}-\mathrm{H}$ bond is about $413 \mathrm{~kJ} / \mathrm{mol}$ in $\mathrm{CH}_{4}$ but $380 \mathrm{~kJ} / \mathrm{mol}$ in $\mathrm{CHBr}_{3}$. Although these values are relatively close in magnitude, they are different. Explain why they are different. Does the fact that the bond energy is lower in $\mathrm{CHBr}_{3}$ make any sense? Why?

LJ

Lena Jake

Numerade Educator

Problem 5

Consider the following statement: "Because oxygen wants to have a negative two charge, the second electron affinity is more negative than the first." Indicate everything that is correct in this statement. Indicate everything that is incorrect. Correct the incorrect statements and explain.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 6

Which has the greater bond lengths: $\mathrm{NO}_{2}^{-}$ or $\mathrm{NO}_{3}^{-}$ ? Explain.

LJ

Lena Jake

Numerade Educator

Problem 7

The following ions are best described with resonance structures. Draw the resonance structures, and using formal charge arguments, predict the best Lewis structure for each ion.
a. $\mathrm{NCO}^{-}$
b. $\mathrm{CNO}^{-}$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 8

Would you expect the electronegativity of titanium to be the same in the species $\mathrm{Ti}, \mathrm{Ti}^{2+}, \mathrm{Ti}^{3+}$, and $\mathrm{Ti}^{4+} ?$ Explain.

Lottie Adams

Numerade Educator

Problem 9

The second electron affinity values for both oxygen and sulfur are unfavorable (endothermic). Explain.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 10

What is meant by a chemical bond? Why do atoms form bonds with each other? Why do some elements exist as molecules in nature instead of as free atoms?

LJ

Lena Jake

Numerade Educator

Problem 11

Why are some bonds ionic and some covalent?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 12

How does a bond between Na and $\mathrm{Cl}$ differ from a bond between
$\mathrm{C}$ and $\mathrm{O}$ ? What about a bond between $\mathrm{N}$ and $\mathrm{N}$ ?

LJ

Lena Jake

Numerade Educator

Problem 13

Arrange the following molecules from most to least polar and explain your order: $\mathrm{CH}_{4}, \mathrm{CF}_{2} \mathrm{Cl}_{2}, \mathrm{CF}_{2} \mathrm{H}_{2}, \mathrm{CCl}_{4}$, and $\mathrm{CCl}_{2} \mathrm{H}_{2}$.

Lottie Adams

Numerade Educator

Problem 14

Does a Lewis structure tell which electrons come from which atoms? Explain.

LM

Leslee Manner

Numerade Educator

Problem 15

Compare and contrast the bonding found in the $\mathrm{H}_{2}(\mathrm{~g})$ and $\mathrm{HF}(\mathrm{g})$ molecules with that found in $\operatorname{NaF}(s)$.

Ethan Brown

Numerade Educator

Problem 16

Describe the type of bonding that exists in the $\mathrm{Cl}_{2}(g)$ molecule. How does this type of bonding differ from that found in the HCl( $g$ ) molecule? How is it similar?

Ethan Brown

Numerade Educator

Problem 17

Some plant fertilizer compounds are $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}, \mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}, \mathrm{~K}_{2} \mathrm{O}$,
$\mathrm{P}_{2} \mathrm{O}_{5}$, and $\mathrm{KCl}$. Which of these compounds contain both ionic and covalent bonds?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 18

Some of the important properties of ionic compounds are as follows:
i. low electrical conductivity as solids and high conductivity in solution or when molten
ii. relatively high melting and boiling points
iii. brittleness iv. solubility in polar solvents How does the concept of ionic bonding discussed in this chapter account for these properties?

LJ

Lena Jake

Numerade Educator

Problem 19

What is the electronegativity trend? Where does hydrogen fit into the electronegativity trend for the other elements in the periodic table?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 20

Give one example of a compound having a linear molecular structure that has an overall dipole moment (is polar) and one example that does not have an overall dipole moment (is nonpolar). Do the same for molecules that have trigonal planar and tetrahedral molecular structures.

LJ

Lena Jake

Numerade Educator

Problem 21

When comparing the size of different ions, the general radii trend discussed in Chapter 7 is usually not very useful. What do you concentrate on when comparing sizes of ions to each other or when comparing the size of an ion to its neutral atom?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 22

In general, the higher the charge on the ions in an ionic compound, the more favorable the lattice energy. Why do some stable ionic compounds have $+1$ charged ions even though $+4,+5$, and $+6$ charged ions would have a more favorable lattice energy?

LJ

Lena Jake

Numerade Educator

Problem 23

Combustion reactions of fossil fuels provide most of the energy needs of the world. Why are combustion reactions of fossil fuels so exothermic?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 24

Which of the following statements is(are) true? Correct the false statements.
a. It is impossible to satisfy the octet rule for all atoms in $\mathrm{XeF}_{2}$.
b. Because $\mathrm{SF}_{4}$ exists, $\mathrm{OF}_{4}$ should also exist because oxygen is in the same family as sulfur.
c. The bond in $\mathrm{NO}^{+}$ should be stronger than the bond in $\mathrm{NO}^{-}$.
d. As predicted from the two Lewis structures for ozone, one oxygen-oxygen bond is stronger than the other oxygenoxygen bond.

Nicole Mabante

Numerade Educator

Problem 25

Three resonance structures can be drawn for $\mathrm{CO}_{2}$. Which resonance structure is best from a formal charge standpoint?

LJ

Lena Jake

Numerade Educator

Problem 26

Which of the following statements is(are) true? Correct the false statements.
a. The molecules $\mathrm{SeS}_{3}, \mathrm{SeS}_{2}, \mathrm{PCl}_{5}, \mathrm{TeCl}_{4}, \mathrm{ICl}_{3}$, and $\mathrm{XeCl}_{2}$ all
exhibit at least one bond angle which is approximately $120^{\circ}$
b. The bond angle in $\mathrm{SO}_{2}$ should be similar to the bond angle in $\mathrm{CS}_{2}$ or $\mathrm{SCl}_{2}$
c. Of the compounds $\mathrm{CF}_{4}, \mathrm{KrF}_{4}$, and $\mathrm{SeF}_{4}$, only $\mathrm{SeF}_{4}$ exhibits an overall dipole moment (is polar).
d. Central atoms in a molecule adopt a geometry of the bonded atoms and lone pairs about the central atom in order to maximize electron repulsions.

Lottie Adams

Numerade Educator

Problem 27

Without using Fig. $8.3$, predict the order of increasing electronegativity in each of the following groups of elements.
a. $\mathrm{C}, \mathrm{N}, \mathrm{O}$
c. $\mathrm{Si}, \mathrm{Ge}, \mathrm{Sn}$
b. $\mathrm{S}, \mathrm{Se}, \mathrm{Cl}$
d. Tl, S, Ge

Nicole Mabante

Numerade Educator

Problem 28

Without using Fig. $8.3$, predict the order of increasing electronegativity in each of the following groups of elements.
a. $\mathrm{Na}, \mathrm{K}, \mathrm{Rb}$
c. $\mathrm{F}, \mathrm{Cl}, \mathrm{Br}$
b. $\mathrm{B}, \mathrm{O}, \mathrm{Ga}$
d. $\mathrm{S}, \mathrm{O}, \mathrm{F}$

LJ

Lena Jake

Numerade Educator

Problem 29

Without using Fig. 8.3, predict which bond in each of the following groups will be the most polar.
a. $\mathrm{C}-\mathrm{F}, \mathrm{Si}-\mathrm{F}, \mathrm{Ge}-\mathrm{F}$
b. $\mathrm{P}-\mathrm{Cl}$ or $\mathrm{S}-\mathrm{Cl}$
c. $\mathrm{S}-\mathrm{F}, \mathrm{S}-\mathrm{Cl}, \mathrm{S}-\mathrm{Br}$
d. $\mathrm{Ti}-\mathrm{Cl}, \mathrm{Si}-\mathrm{Cl}, \mathrm{Ge}-\mathrm{Cl}$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 30

Without using Fig. $8.3$, predict which bond in each of the following groups will be the most polar.
a. $\mathrm{C}-\mathrm{H}, \mathrm{Si}-\mathrm{H}, \mathrm{Sn}-\mathrm{H}$
b. $\mathrm{Al}-\mathrm{Br}, \mathrm{Ga}-\mathrm{Br}, \mathrm{In}-\mathrm{Br}, \mathrm{Tl}-\mathrm{Br}$
c. $\mathrm{C}-\mathrm{O}$ or $\mathrm{Si}-\mathrm{O}$
d. $\mathrm{O}-\mathrm{F}$ or $\mathrm{O}-\mathrm{Cl}$

LJ

Lena Jake

Numerade Educator

Problem 31

Repeat Exercises 27 and 29 , this time using the values for the electronegativities of the elements given in Fig. 8.3. Are there differences in your answers?

Brooke Smith

Numerade Educator

Problem 32

Repeat Exercises 28 and 30 , this time using the values for the electronegativities of the elements given in Fig. 8.3. Are there differences in your answers?

Brooke Smith

Numerade Educator

Problem 33

Which of the following incorrectly shows the bond polarity? Show the correct bond polarity for those that are incorrect.
a. $^{8+} \mathrm{H}-\mathrm{F}^{\delta-}$
d. $^{\delta}+\mathrm{Br}-\mathrm{Br}^{8}$
b. $^{\delta+} \mathrm{Cl}-\mathrm{I}^{8}-$
e. $^{\delta+} \mathrm{O}-\mathrm{P}^{\delta-}$
c. $^{\delta+} \mathrm{Si}-\mathrm{S}^{8-}$

Anand Jangid

Numerade Educator

Problem 34

Indicate the bond polarity (show the partial positive and partial negative ends) in the following bonds.
a. $\mathrm{C}-\mathrm{O}$
d. $\mathrm{Br}-\mathrm{Te}$
b. $\mathrm{P}-\mathrm{H}$
e. $\mathrm{Se}-\mathrm{S}$
c. $\mathrm{H}-\mathrm{Cl}$

LJ

Lena Jake

Numerade Educator

Problem 35

Predict the type of bond (ionic, covalent, or polar covalent) one would expect to form between the following pairs of elements.
a. $\mathrm{Rb}$ and $\mathrm{Cl}$
d. $\mathrm{Ba}$ and $\mathrm{S}$
b. $S$ and $S$
e. $\mathrm{N}$ and $\mathrm{P}$
c. $C$ and $\bar{F}$
f. $\mathrm{B}$ and $\mathrm{H}$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 36

List all the possible bonds that can occur between the elements $\mathrm{P}, \mathrm{Cs}, \mathrm{O}$, and $\mathrm{H}$. Predict the type of bond (ionic, covalent, or polar covalent) one would expect to form for each bond.

LJ

Lena Jake

Numerade Educator

Problem 37

Hydrogen has an electronegativity value between boron and carbon and identical to phosphorus. With this in mind, rank the following bonds in order of decreasing polarity: $\mathrm{P}-\mathrm{H}, \mathrm{O}-\mathrm{H}$, $\mathrm{N}-\mathrm{H}, \mathrm{F}-\mathrm{H}, \mathrm{C}-\mathrm{H}$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 38

Rank the following bonds in order of increasing ionic character:
$\mathrm{N}-\mathrm{O}, \mathrm{Ca}-\mathrm{O}, \mathrm{C}-\mathrm{F}, \mathrm{Br}-\mathrm{Br}, \mathrm{K}-\mathrm{F}$.

LJ

Lena Jake

Numerade Educator

Problem 39

Write electron configurations for the most stable ion formed by each of the elements Rb, Ba, Se, and I (when in stable ionic compounds).

Lottie Adams

Numerade Educator

Problem 40

Write electron configurations for the most stable ion formed by each of the elements Te, $\mathrm{Cl}, \mathrm{Sr}$, and $\mathrm{Li}$ (when in stable ionic compounds).

LJ

Lena Jake

Numerade Educator

Problem 41

Predict the empirical formulas of the ionic compounds formed from the following pairs of elements. Name each compound.
a. $\mathrm{Li}$ and $\mathrm{N}$
c. $\mathrm{Rb}$ and $\mathrm{Cl}$
b. Ga and $\mathrm{O}$
d. $\mathrm{Ba}$ and $\mathrm{S}$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 42

Predict the empirical formulas of the ionic compounds formed from the following pairs of elements. Name each compound.
a. $\mathrm{Al}$ and $\mathrm{Cl}$
c. $\mathrm{Sr}$ and $\mathrm{F}$
b. $\mathrm{Na}$ and $\mathrm{O}$
d. Ca and Se

LJ

Lena Jake

Numerade Educator

Problem 43

Write electron configurations for
a. the cations $\mathrm{Mg}^{2+}, \mathrm{K}^{+}$, and $\mathrm{Al}^{3+}$.
b. the anions $\mathrm{N}^{3-}, \mathrm{O}^{2-}, \mathrm{F}^{-}$, and $\mathrm{Te}^{2-}$.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 44

Write electron configurations for
a. the cations $\mathrm{Sr}^{2+}, \mathrm{Cs}^{+}, \mathrm{In}^{+}$, and $\mathrm{Pb}^{2+}$.
b. the anions $\mathrm{P}^{3-}, \mathrm{S}^{2-}$, and $\mathrm{Br}^{-}$.

LJ

Lena Jake

Numerade Educator

Problem 45

Which of the following ions have noble gas electron configurations?
a. $\mathrm{Fe}^{2+}, \mathrm{Fe}^{3+}, \mathrm{Sc}^{3+}, \mathrm{Co}^{3+}$
b. $\mathrm{Tl}^{+}, \mathrm{Te}^{2-}, \mathrm{Cr}^{3+}$
c. $\mathrm{Pu}^{4+}, \mathrm{Ce}^{4+}, \mathrm{Ti}^{4+}$
d. $\mathrm{Ba}^{2+}, \mathrm{Pt}^{2+}, \mathrm{Mn}^{2+}$

Bryan Li

Numerade Educator

Problem 46

What noble gas has the same election configuration as each of the ions in the following compounds?
a. cesium sulfide
b. strontium fluoride
c. calcium nitride
d. aluminum bromide

LJ

Lena Jake

Numerade Educator

Problem 47

Give the formula of a negative ion that would have the same number of electrons as each of the following positive ions.
a. $\mathrm{Na}^{+}$
c. $\mathrm{Al}^{3+}$
b. $\mathrm{Ca}^{2+}$
d. $\mathrm{Rb}^{+}$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 48

Give an example of an ionic compound where both the anion and the cation are isoelectronic with each of the following noble
gases.
a. Ne
c. $\mathrm{Kr}$
b. $\mathrm{Ar}$
d. Xe

David Collins

Numerade Educator

Problem 49

Give three ions that are isoelectronic with neon. Place these ions in order of increasing size.

Chase Crook

Numerade Educator

Problem 50

Consider the ions $\mathrm{Sc}^{3+}, \mathrm{Cl}^{-}, \mathrm{K}^{+}, \mathrm{Ca}^{2+}$, and $\mathrm{S}^{2-} .$ Match these ions to the following pictures that represent the relative sizes of the ions.

Chase Crook

Numerade Educator

Problem 51

For each of the following groups, place the atoms and/or ions in order of decreasing size.
a. $\mathrm{Cu}, \mathrm{Cu}^{+}, \mathrm{Cu}^{2+}$
b. $\mathrm{Ni}^{2+}, \mathrm{Pd}^{2+}, \mathrm{Pt}^{2+}$
c. $\mathrm{O}, \mathrm{O}^{-}, \mathrm{O}^{2-}$
d. $\mathrm{La}^{3+}, \mathrm{Eu}^{3+}, \mathrm{Gd}^{3+}, \mathrm{Yb}^{3+}$
e. $\mathrm{Te}^{2-}, \mathrm{I}^{-}, \mathrm{Cs}^{+}, \mathrm{Ba}^{2+}, \mathrm{La}^{3+}$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 52

For each of the following groups, place the atoms and/or ions in order of decreasing size.
a. $\mathrm{V}, \mathrm{V}^{2+}, \mathrm{V}^{3+}, \mathrm{V}^{5+}$
b. $\mathrm{Na}^{+}, \mathrm{K}^{+}, \mathrm{Rb}^{+}, \mathrm{Cs}^{+}$
c. $\mathrm{Te}^{2-}, \mathrm{I}^{-}, \mathrm{Cs}^{+}, \mathrm{Ba}^{2+}$
d. $\mathrm{P}, \mathrm{P}^{-}, \mathrm{P}^{2-}, \mathrm{P}^{3-}$
e. $\mathrm{O}^{2-}, \mathrm{S}^{2-}, \mathrm{Se}^{2-}, \mathrm{Te}^{2-}$

David Collins

Numerade Educator

Problem 53

Which compound in each of the following pairs of ionic substances has the most exothermic lattice energy? Justify your answers.
a. $\mathrm{NaCl}, \mathrm{KCl}$
b. $\mathrm{LiF}, \mathrm{LiCl}$
c. $\mathrm{Mg}(\mathrm{OH})_{2}, \mathrm{MgO}$
d. $\mathrm{Fe}(\mathrm{OH})_{2}, \mathrm{Fe}(\mathrm{OH})_{3}$
e. $\mathrm{NaCl}, \mathrm{Na}_{2} \mathrm{O}$
f. $\mathrm{MgO}, \mathrm{BaS}$

Nicole Mabante

Numerade Educator

Problem 54

Which compound in each of the following pairs of ionic substances has the most exothermic lattice energy? Justify your answers.
a. $\mathrm{LiF}, \mathrm{CsF}$
b. NaBr, NaI
c. $\mathrm{BaCl}_{2}, \mathrm{BaO}$
d. $\mathrm{Na}_{2} \mathrm{SO}_{4}, \mathrm{CaSO}_{4}$
e. $\mathrm{KF}, \mathrm{K}_{2} \mathrm{O}$
f. $\mathrm{Li}_{2} \mathrm{O}, \mathrm{Na}_{2} \mathrm{~S}$

Nicole Mabante

Numerade Educator

Problem 55

Use the following data to estimate $\Delta H_{\mathrm{f}}^{\circ}$ for potassium chloride.
$$
\mathrm{K}(s)+\frac{1}{2} \mathrm{Cl}_{2}(g) \longrightarrow \mathrm{KCl}(s)
$$
$$
\begin{array}{lr}
\text { Lattice energy } & -690 . \mathrm{kJ} / \mathrm{mol} \\
\text { Ionization energy for } \mathrm{K} & 419 \mathrm{~kJ} / \mathrm{mol} \\
\text { Electron affinity of Cl } & -349 \mathrm{~kJ} / \mathrm{mol} \\
\text { Bond energy of } \mathrm{Cl}_{2} & 239 \mathrm{~kJ} / \mathrm{mol} \\
\text { Enthalpy of sublimation for } \mathrm{K} & 64 \mathrm{~kJ} / \mathrm{mol}
\end{array}
$$

Nicole Smina

Numerade Educator

Problem 56

Use the following data to estimate $\Delta H_{\mathrm{f}}^{\circ}$ for magnesium fluoride.
$$
\mathrm{Mg}(s)+\mathrm{F}_{2}(g) \longrightarrow \mathrm{MgF}_{2}(s)
$$
$$
\begin{array}{lr}
\text { Lattice energy } & -2913 \mathrm{~kJ} / \mathrm{mol} \\
\text { First ionization energy of } \mathrm{Mg} & 735 \mathrm{~kJ} / \mathrm{mol} \\
\text { Second ionization energy of } \mathrm{Mg} & 1445 \mathrm{~kJ} / \mathrm{mol} \\
\text { Electron affinity of } \mathrm{F} & -328 \mathrm{~kJ} / \mathrm{mol} \\
\text { Bond energy of } \mathrm{F}_{2} & 154 \mathrm{~kJ} / \mathrm{mol} \\
\text { Enthalpy of sublimation for } \mathrm{Mg} & 150 . \mathrm{kJ} / \mathrm{mol}
\end{array}
$$

LJ

Lena Jake

Numerade Educator

Problem 57

Consider the following energy changes:
Magnesium oxide exists as $\mathrm{Mg}^{2+} \mathrm{O}^{2-}$ and not as $\mathrm{Mg}^{+} \mathrm{O}^{-}$. Explain.

Vishal Sharma

Numerade Educator

Problem 58

Compare the electron affinity of fluorine to the ionization energy of sodium. Is the process of an electron being "pulled" from the sodium atom to the fluorine atom exothermic or endothermic? Why is NaF a stable compound? Is the overall formation of NaF endothermic or exothermic? How can this be?

LJ

Lena Jake

Numerade Educator

Problem 59

$\operatorname{LiI}(s)$ has a heat of formation of $-272 \mathrm{~kJ} / \mathrm{mol}$ and a lattice energy of $-753 \mathrm{~kJ} / \mathrm{mol}$. The ionization energy of $\mathrm{Li}(g)$ is 520 . $\mathrm{kJ} / \mathrm{mol}$, the bond energy of $\mathrm{I}_{2}(g)$ is $151 \mathrm{~kJ} / \mathrm{mol}$, and the electron affinity of $\mathrm{I}(g)$ is $-295 \mathrm{~kJ} / \mathrm{mol}$. Use these data to determine the heat of sublimation of $\operatorname{Li}(s)$.

Julian Taurozzi

Julian Taurozzi

Numerade Educator

Problem 60

Use the following data to estimate $\Delta H$ for the reaction $\mathrm{S}^{-}(g)+$ $\mathrm{e}^{-} \rightarrow \mathrm{S}^{2-}(g)$. Include an estimate of uncertainty.
$$
\begin{array}{|lcccc|}
\hline & & \text { Lattice } & & \Delta H_{\text {sub }} \\
& \Delta \boldsymbol{H}_{\mathrm{t}}^{\circ} & \text { Energy } & \text { I.E. of } \mathbf{M} & \text { of M } \\
\hline \mathrm{Na}_{2} \mathrm{~S} & -365 & -2203 & 495 & 109 \\
\mathrm{~K}_{2} \mathrm{~S} & -381 & -2052 & 419 & 90 \\
\mathrm{Rb}_{2} \mathrm{~S} & -361 & -1949 & 409 & 82 \\
\mathrm{Cs}_{2} \mathrm{~S} & -360 & -1850 & 382 & 78 \\
\hline
\end{array}
$$
$$
\begin{aligned}
\mathrm{S}(s) & \longrightarrow \mathrm{S}(g) & \Delta H &=227 \mathrm{~kJ} / \mathrm{mol} \\
\mathrm{S}(g)+\mathrm{e}^{-} & \longrightarrow \mathrm{S}^{-}(g) & \Delta H &=-200 \mathrm{~kJ} / \mathrm{mol}
\end{aligned}
$$
Assume that all values are known to $\pm 1 \mathrm{~kJ} / \mathrm{mol}$.

David Collins

Numerade Educator

Problem 61

Rationalize the following lattice energy values:
$$
\begin{array}{|lc|}
\hline & \text { Lattice Energy } \\
\text { Compound } & (\mathrm{kJ} / \mathrm{mol}) \\
\hline \mathrm{CaSe} & -2862 \\
\mathrm{Na}_{2} \mathrm{Se} & -2130 \\
\mathrm{CaTe} & -2721 \\
\mathrm{Na}_{2} \mathrm{Te} & -2095 \\
\hline
\end{array}
$$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 62

The lattice energies of $\mathrm{FeCl}_{3}, \mathrm{FeCl}_{2}$, and $\mathrm{Fe}_{2} \mathrm{O}_{3}$ are (in no particular order $-2631,-5359$, and $-14,774 \mathrm{~kJ} / \mathrm{mol}$. Match the appropriate formula to each lattice energy. Explain.

LJ

Lena Jake

Numerade Educator

Problem 63

Use bond energy values (Table $8.4$ ) to estimate $\Delta H$ for each of the following reactions in the gas phase.
a. $\mathrm{H}_{2}+\mathrm{Cl}_{2} \rightarrow 2 \mathrm{HCl}$
b. $\mathrm{N} \equiv \mathrm{N}+3 \mathrm{H}_{2} \rightarrow 2 \mathrm{NH}_{3}$

Nicole Mabante

Numerade Educator

Problem 64

Use bond energy values (Table 8.4) to estimate $\Delta H$ for each of the following reactions.

Nicole Mabante

Numerade Educator

Problem 65

Use bond energies (Table 8.4) to predict $\Delta H$ for the isomerization of methyl isocyanide to acetonitrile:
$$
\mathrm{CH}_{3} \mathrm{~N} \equiv \mathrm{C}(g) \longrightarrow \mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{N}(g)
$$

Nicole Mabante

Numerade Educator

Problem 66

Acetic acid is responsible for the sour taste of vinegar. It can be manufactured using the following reaction:
Use tabulated values of bond energies (Table $8.4$ ) to estimate $\Delta H$ for this reaction.

Nicole Mabante

Numerade Educator

Problem 67

Use bond energies to predict $\Delta H$ for the following reaction:
$$
\mathrm{H}_{2} \mathrm{~S}(g)+3 \mathrm{~F}_{2}(g) \longrightarrow \mathrm{SF}_{4}(g)+2 \mathrm{HF}(g)
$$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 68

The major industrial source of hydrogen gas is by the following reaction:
$$
\mathrm{CH}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow \mathrm{CO}(g)+3 \mathrm{H}_{2}(g)
$$
Use bond energies to predict $\Delta H$ for this reaction.

LJ

Lena Jake

Numerade Educator

Problem 69

Use bond energies to estimate $\Delta H$ for the combustion of one mole of acetylene:
$$
\mathrm{C}_{2} \mathrm{H}_{2}(g)+\frac{5}{2} \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)
$$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 70

The space shuttle orbiter utilizes the oxidation of methyl hydrazine by dinitrogen tetroxide for propulsion:
$5 \mathrm{~N}_{2} \mathrm{O}_{4}(g)+4 \mathrm{~N}_{2} \mathrm{H}_{3} \mathrm{CH}_{3}(g) \longrightarrow 12 \mathrm{H}_{2} \mathrm{O}(g)+9 \mathrm{~N}_{2}(g)+4 \mathrm{CO}_{2}(g)$
Use bond energies to estimate $\Delta H$ for this reaction. The structures for the reactants are:

David Collins

Numerade Educator

Problem 71

Consider the following reaction:
Estimate the carbon-fluorine bond energy given that the $\mathrm{C}-\mathrm{C}$ bond energy is $347 \mathrm{~kJ} / \mathrm{mol}$, the $\mathrm{C}=\mathrm{C}$ bond energy is $614 \mathrm{~kJ} / \mathrm{mol}$, and the $\mathrm{F}-\mathrm{F}$ bond energy is $154 \mathrm{~kJ} / \mathrm{mol}$.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 72

Consider the following reaction:
$$
\mathrm{A}_{2}+\mathrm{B}_{2} \longrightarrow 2 \mathrm{AB} \quad \Delta H=-285 \mathrm{~kJ}
$$
The bond energy for $\mathrm{A}_{2}$ is one-half the amount of the $\mathrm{AB}$ bond energy. The bond energy of $\mathrm{B}_{2}=432 \mathrm{~kJ} / \mathrm{mol}$. What is the bond energy of $\mathrm{A}_{2}$ ?

LJ

Lena Jake

Numerade Educator

Problem 73

Compare your answers from parts a and $\mathrm{b}$ of Exercise 63 with $\Delta H$ values calculated for each reaction using standard enthalpies of formation in Appendix 4 . Do enthalpy changes calculated from bond energies give a reasonable estimate of the actual values?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 74

Compare your answer from Exercise 66 to the $\Delta H$ value calculated from standard enthalpies of formation in Appendix $4 .$ Explain any discrepancies.

LJ

Lena Jake

Numerade Educator

Problem 75

The standard enthalpies of formation for $\mathrm{S}(g), \mathrm{F}(g), \mathrm{SF}_{4}(g)$, and $\mathrm{SF}_{6}(g)$ are $+278.8,+79.0,-775$, and $-1209 \mathrm{~kJ} / \mathrm{mol}$, respectively.
a. Use these data to estimate the energy of an $\mathrm{S}-\mathrm{F}$ bond.
b. Compare your calculated value to the value given in Table $8.4$. What conclusions can you draw?
c. Why are the $\Delta H_{\mathrm{f}}^{\circ}$ values for $\mathrm{S}(g)$ and $\mathrm{F}(g)$ not equal to zero, since sulfur and fluorine are elements?

Julian Taurozzi

Julian Taurozzi

Numerade Educator

Problem 76

Use the following standard enthalpies of formation to estimate the $\mathrm{N}-\mathrm{H}$ bond energy in ammonia: $\mathrm{N}(\mathrm{g}), 472.7 \mathrm{~kJ} / \mathrm{mol} ; \mathrm{H}(\mathrm{g})$,
$216.0 \mathrm{~kJ} / \mathrm{mol} ; \mathrm{NH}_{3}(g),-46.1 \mathrm{~kJ} / \mathrm{mol}$. Compare your value to the
one in Table $8.4$.

Brooke Smith

Numerade Educator

Problem 77

The standard enthalpy of formation for $\mathrm{N}_{2} \mathrm{H}_{4}(g)$ is $95.4 \mathrm{~kJ} / \mathrm{mol}$. Use this and the data in Exercise 76 to estimate the $\mathrm{N}-\mathrm{N}$ single bond energy. Compare this with the value in Table $8.4$.

Brooke Smith

Numerade Educator

Problem 78

The standard enthalpy of formation for $\mathrm{NO}(g)$ is $90 . \mathrm{kJ} / \mathrm{mol}$. Use this and the values for the $\mathrm{O}=\mathrm{O}$ and $\mathrm{N} \equiv \mathrm{N}$ bond energies to estimate the bond strength in NO.

LJ

Lena Jake

Numerade Educator

Problem 79

Write Lewis structures that obey the octet rule (duet rule for $\mathrm{H}$ ) for each of the following molecules. Carbon is the central atom in $\mathrm{CH}_{4}$, nitrogen is the central atom in $\mathrm{NH}_{3}$, and oxygen is the central atom in $\mathrm{H}_{2} \mathrm{O}$.
a. $\mathrm{F}_{2}$
e. $\mathrm{NH}_{3}$
b. $\mathrm{O}_{2}$
f. $\mathrm{H}_{2} \mathrm{O}$
c. $\mathrm{CO}$
g. HF
d. $\mathrm{CH}_{4}$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 80

Write Lewis structures that obey the octet rule (duet rule for $\mathrm{H}$ ) for each of the following molecules.
a. $\mathrm{H}_{2} \mathrm{CO}$
b. $\mathrm{CO}_{2}$
c. HCN Except for $\mathrm{HCN}$ and $\mathrm{H}_{2} \mathrm{CO}$, the first atom listed is the central atom. For $\mathrm{HCN}$ and $\mathrm{H}_{2} \mathrm{CO}$, carbon is the central atom. Carbon is the central atom in all of these molecules.

Chase Crook

Numerade Educator

Problem 81

Write Lewis structures that obey the octet rule for each of the following molecules.
a. $\mathrm{CCl}_{4}$
c. $\mathrm{SeCl}_{2}$
b. $\mathrm{NCl}_{3}$
d. $\mathrm{ICl}$
In each case, the atom listed first is the central atom.

Nicole Smina

Numerade Educator

Problem 82

Write Lewis structures that obey the octet rule for each of the following molecules and ions. (In each case the first atom listed is the central atom.)
a. $\mathrm{POCl}_{3}, \mathrm{SO}_{4}^{2-}, \mathrm{XeO}_{4}, \mathrm{PO}_{4}^{3-}, \mathrm{ClO}_{4}^{-}$
b. $\mathrm{NF}_{3}, \mathrm{SO}_{3}^{2-}, \mathrm{PO}_{3}{ }^{3-}, \mathrm{ClO}_{3}^{-}$
c. $\mathrm{ClO}_{2}^{-}, \mathrm{SCl}_{2}, \mathrm{PCl}_{2}^{-}$
d. Considering your answers to parts $\mathrm{a}, \mathrm{b}$, and $\mathrm{c}$, what conclusions can you draw concerning the structures of species containing the same number of atoms and the same number of valence electrons?

Chase Crook

Numerade Educator

Problem 83

One type of exception to the octet rule are compounds with central atoms having fewer than eight electrons around them. $\mathrm{BeH}_{2}$ and $\mathrm{BH}_{3}$ are examples of this type of exception. Draw the Lewis structures for $\mathrm{BeH}_{2}$ and $\mathrm{BH}_{3}$.

Chase Crook

Numerade Educator

Problem 84

Lewis structures can be used to understand why some molecules react in certain ways. Write the Lewis structures for the reactants and products in the reactions described below.
a. Nitrogen dioxide dimerizes to produce dinitrogen tetroxide.
b. Boron trihydride accepts a pair of electrons from ammonia, forming $\mathrm{BH}_{3} \mathrm{NH}_{3}$
Give a possible explanation for why these two reactions occur.

LJ

Lena Jake

Numerade Educator

Problem 85

The most common type of exception to the octet rule are compounds or ions with central atoms having more than eight electrons around them. $\mathrm{PF}_{5}, \mathrm{SF}_{4}, \mathrm{ClF}_{3}$ and $\mathrm{Br}_{3}^{-}$ are examples of this type of exception. Draw the Lewis structure for these compounds on ions. Which elements, when they have to, can have more than eight electrons around them? How is this rationalized?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 86

$\mathrm{SF}_{6}, \mathrm{ClF}_{5}$, and $\mathrm{XeF}_{4}$ are three compounds whose central atoms do not follow the octet rule. Draw Lewis structures for these compounds.

LM

Leslee Manner

Numerade Educator

Problem 87

Write Lewis structures for the following. Show all resonance structures where applicable.
a. $\mathrm{NO}_{2}^{-}, \mathrm{NO}_{3}^{-}, \mathrm{N}_{2} \mathrm{O}_{4}\left(\mathrm{~N}_{2} \mathrm{O}_{4}\right.$ exists as $\mathrm{O}_{2} \mathrm{~N}-\mathrm{NO}_{2} .$ )
b. $\mathrm{OCN}^{-}, \mathrm{SCN}^{-}, \mathrm{N}_{3}^{-}$ (Carbon is the central atom in $\mathrm{OCN}^{-}$ and $\left.\mathrm{SCN}^{-} .\right)$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 88

Some of the important pollutants in the atmosphere are ozone $\left(\mathrm{O}_{3}\right)$, sulfur dioxide, and sulfur trioxide. Write Lewis structures for these three molecules. Show all resonance structures where applicable.

LJ

Lena Jake

Numerade Educator

Problem 89

Benzene $\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)$ consists of a six-membered ring of carbon atoms with one hydrogen bonded to each carbon. Write Lewis structures for benzene, including resonance structures.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 90

Borazine $\left(\mathrm{B}_{3} \mathrm{~N}_{3} \mathrm{H}_{6}\right)$ has often been called "inorganic" benzene. Write Lewis structures for borazine. Borazine contains a sixmembered ring of alternating boron and nitrogen atoms with one hydrogen bonded to each boron and nitrogen.

Chase Crook

Numerade Educator

Problem 91

An important observation supporting the concept of resonance in the localized electron model was that there are only three different structures of dichlorobenzene $\left(\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{Cl}_{2}\right)$. How does this fact support the concept of resonance (see Exercise 89)?

Vishal Sharma

Numerade Educator

Problem 92

Consider the following bond lengths:
$\begin{array}{lllll}\mathrm{C}-\mathrm{O} & 143 \mathrm{pm} & \mathrm{C}=\mathrm{O} & 123 \mathrm{pm} & \mathrm{C} \equiv \mathrm{O} & 109 \mathrm{pm}\end{array}$
In the $\mathrm{CO}_{3}^{2-}$ ion, all three $\mathrm{C}-\mathrm{O}$ bonds have identical bond lengths of $136 \mathrm{pm}$. Why?

Vishal Sharma

Numerade Educator

Problem 93

Order the following species with respect to carbon-oxygen bond length (longest to shortest).
$$
\mathrm{CO}, \quad \mathrm{CO}_{2}, \quad \mathrm{CO}_{3}{ }^{2-}, \quad \mathrm{CH}_{3} \mathrm{OH}
$$
What is the order from the weakest to the strongest carbonoxygen bond? $\left(\mathrm{CH}_{3} \mathrm{OH}\right.$ exists as $\mathrm{H}_{3} \mathrm{C}-\mathrm{OH}$.)

Vishal Sharma

Numerade Educator

Problem 94

Place the species below in order of the shortest to the longest nitrogen-oxygen bond.
$\begin{array}{lllll}\mathrm{H}_{2} \mathrm{NOH}, & \mathrm{N}_{2} \mathrm{O}, & \mathrm{NO}^{+}, & \mathrm{NO}_{2}^{-}, & \mathrm{NO}_{3}^{-}\end{array}$
$\left(\mathrm{H}_{2} \mathrm{NOH}\right.$ exists as $\mathrm{H}_{2} \mathrm{~N}-\mathrm{OH} .$.

Nicole Mabante

Numerade Educator

Problem 95

Use the formal charge arguments to rationalize why $\mathrm{BF}_{3}$ would not follow the octet rule.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 96

Use formal charge arguments to explain why $\mathrm{CO}$ has a much smaller dipole moment than would be expected on the basis of electronegativity.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 97

Write Lewis structures that obey the octet rule for the following species. Assign the formal charge for each central atom.
a. $\mathrm{POCl}_{3}$
e. $\mathrm{SO}_{2} \mathrm{Cl}_{2}$
b. $\mathrm{SO}_{4}^{2-}$
f. $\mathrm{XeO}_{4}$
c. $\mathrm{ClO}_{4}^{-}$
g. $\mathrm{ClO}_{3}^{-}$
d. $\mathrm{PO}_{4}^{3-}$
h. $\mathrm{NO}_{4}^{3-}$

Nicole Mabante

Numerade Educator

Problem 98

Write Lewis structures for the species in Exercise 97 that involve minimum formal charges.

LJ

Lena Jake

Numerade Educator

Problem 99

Write the Lewis structure for $\mathrm{O}_{2} \mathrm{~F}_{2}\left(\mathrm{O}_{2} \mathrm{~F}_{2}\right.$ exists as $\left.\mathrm{F}-\mathrm{O}-\mathrm{O}-\mathrm{F}\right)$.
Assign oxidation states and formal charges to the atoms in $\mathrm{O}_{2} \mathrm{~F}_{2}$. This compound is a vigorous and potent oxidizing and fluorinating agent. Are oxidation states or formal charges more useful in accounting for these properties of $\mathrm{O}_{2} \mathrm{~F}_{2}$ ?

Lottie Adams

Numerade Educator

Problem 100

Oxidation of the cyanide ion produces the stable cyanate ion, $\mathrm{OCN}^{-}$. The fulminate ion, $\mathrm{CNO}^{-}$, on the other hand, is very unstable. Fulminate salts explode when struck; $\mathrm{Hg}(\mathrm{CNO})_{2}$ is used in blasting caps. Write the Lewis structures and assign formal charges for the cyanate and fulminate ions. Why is the fulminate ion so unstable? (C is the central atom in $\mathrm{OCN}^{-}$ and $\mathrm{N}$ is the central atom in $\mathrm{CNO}^{-} .$.)

LJ

Lena Jake

Numerade Educator

Problem 101

When molten sulfur reacts with chlorine gas, a vile-smelling orange liquid forms that has an empirical formula of SCl. The structure of this compound has a formal charge of zero on all elements in the compound. Draw the Lewis structure for the vilesmelling orange liquid.

Lottie Adams

Numerade Educator

Problem 102

Nitrous oxide $\left(\mathrm{N}_{2} \mathrm{O}\right)$ has three possible Lewis structures:
Given the following bond lengths,
$$
\begin{array}{llll}
\mathrm{N}-\mathrm{N} & 167 \mathrm{pm} & \mathrm{N}=\mathrm{O} & 115 \mathrm{pm} \\
\mathrm{N}=\mathrm{N} & 120 \mathrm{pm} & \mathrm{N}-\mathrm{O} & 147 \mathrm{pm} \\
\mathrm{N} \equiv \mathrm{N} & 110 \mathrm{pm} & &
\end{array}
$$
rationalize the observations that the $\mathrm{N}-\mathrm{N}$ bond length in $\mathrm{N}_{2} \mathrm{O}$ is $112 \mathrm{pm}$ and that the $\mathrm{N}-\mathrm{O}$ bond length is $119 \mathrm{pm}$. Assign formal charges to the resonance structures for $\mathrm{N}_{2} \mathrm{O}$. Can you eliminate any of the resonance structures on the basis of formal charges? Is this consistent with observation?

Nicole Smina

Numerade Educator

Problem 103

Predict the molecular structure and bond angles for each molecule or ion in Exercises 81 and 87 .

Nicole Mabante

Numerade Educator

Problem 104

Predict the molecular structure and bond angles for each molecule or ion in Exercises 82 and 88 .

Nicole Mabante

Numerade Educator

Problem 105

There are several molecular structures based on the trigonal bipyramid geometry (see Table 8.8). Three such structures are
Which of the compounds in Exercises 85 and 86 have these molecular structures?

Nicole Mabante

Numerade Educator

Problem 106

Two variations of the octahedral geometry (see Table 8.6) are illustrated below.
Which of the compounds in Exercises 85 and 86 have these molecular structures?

Nicole Mabante

Numerade Educator

Problem 107

Predict the molecular structure (including bond angles) for each of the following.
a. $\mathrm{SeO}_{3}$
b. $\mathrm{SeO}_{2}$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 108

Predict the molecular structure (including bond angles) for each of the following.
a. $\mathrm{PCl}_{3}$
b. $\mathrm{SCl}_{2}$
c. $\mathrm{SiF}_{4}$

LJ

Lena Jake

Numerade Educator

Problem 109

Predict the molecular structure (including bond angles) for each of the following. (See Exercises 105 and 106.)
a. $\mathrm{XeCl}_{2}$
b. $\mathrm{ICl}_{3}$
c. $\mathrm{TeF}_{4}$
d. $\mathrm{PCl}_{5}$

Nicole Mabante

Numerade Educator

Problem 110

Predict the molecular structure (including bond angles) for each of the following. (See Exercises 105 and 106.)
a. $\mathrm{ICl}_{5}$
b. $\mathrm{XeCl}_{4}$
c. $\mathrm{SeCl}_{6}$

Nicole Mabante

Numerade Educator

Problem 111

Which of the molecules in Exercise 107 have net dipole moments (are polar)?

LJ

Lena Jake

Numerade Educator

Problem 112

Which of the molecules in Exercise 108 have net dipole moments (are polar)?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 113

Which of the molecules in Exercise 109 have net dipole moments (are polar)?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 114

Which of the molecules in Exercise 110 have net dipole moments (are polar)?

LJ

Lena Jake

Numerade Educator

Problem 115

Write Lewis structures and predict the molecular structures of the following. (See Exercises 105 and 106 .)
a. $\mathrm{OCl}_{2}, \mathrm{KrF}_{2}, \mathrm{BeH}_{2}, \mathrm{SO}_{2}$
b. $\mathrm{SO}_{3}, \mathrm{NF}_{3}, \mathrm{IF}_{3}$
c. $\mathrm{CF}_{4}, \mathrm{SeF}_{4}, \mathrm{KrF}_{4}$
d. $\mathrm{IF}_{5}, \mathrm{AsF}_{5}$
Which of these compounds are polar?

Nicole Mabante

Numerade Educator

Problem 116

Write Lewis structures and predict whether each of the following is polar or nonpolar.
a. HOCN (exists as $\mathrm{HO}-\mathrm{CN}$ )
b. $\operatorname{COS}$
c. $\mathrm{XeF}_{2}$
d. $\mathrm{CF}_{2} \mathrm{Cl}_{2}$
e. $\mathrm{SeF}_{6}$
f. $\mathrm{H}_{2} \mathrm{CO}(\mathrm{C}$ is the central atom. $)$

Lottie Adams

Numerade Educator

Problem 117

Consider the following Lewis structure where $\mathrm{E}$ is an unknown element:
What are some possible identities for element E? Predict the molecular structure (including bond angles) for this ion.

Lottie Adams

Numerade Educator

Problem 118

Consider the following Lewis structure where $\mathrm{E}$ is an unknown element:
What are some possible identities for element E? Predict the molecular structure (including bond angles) for this ion. (See Exercises 105 and $106 .$ )

Nicole Mabante

Numerade Educator

Problem 119

The molecules $\mathrm{BF}_{3}, \mathrm{CF}_{4}, \mathrm{CO}_{2}, \mathrm{PF}_{5}$, and $\mathrm{SF}_{6}$ are all nonpolar,
even though they all contain polar bonds. Why?

Lottie Adams

Numerade Educator

Problem 120

Two different compounds have the formula $\mathrm{XeF}_{2} \mathrm{Cl}_{2} .$ Write Lewis structures for these two compounds, and describe how measurement of dipole moments might be used to distinguish between them.

Lottie Adams

Numerade Educator

Problem 121

The alkali metal ions are very important for the proper functioning of biologic systems, such as nerves and muscles, and $\mathrm{Na}^{+}$ and $\mathrm{K}^{+}$ ions are present in all body cells and fluids. In human blood plasma, the concentrations are
$$
\left[\mathrm{Na}^{+}\right] \approx 0.15 M \text { and }\left[\mathrm{K}^{+}\right] \approx 0.005 M
$$
For the fluids inside the cells, the concentrations are reversed:
$$
\left[\mathrm{Na}^{+}\right] \approx 0.005 M \text { and }\left[\mathrm{K}^{+}\right] \approx 0.16 M
$$
Since the concentrations are so different inside and outside the cells, an elaborate mechanism is needed to transport $\mathrm{Na}^{+}$ and $\mathrm{K}^{+}$ ions through the cell membranes. What are the ground-state electron configurations for $\mathrm{Na}^{+}$ and $\mathrm{K}^{+}$ ? Which ion is smaller in size? Counterions also must be present in blood plasma and inside intracellular fluid. Assume the counterion present to balance the positive charge of $\mathrm{Na}^{+}$ and $\mathrm{K}^{+}$ is $\mathrm{Cl}^{-}$. What is the ground-state electron configuration for $\mathrm{Cl}^{-}$ ? Rank these three ions in order of increasing size.

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 122

Producing ethanol as a biofuel from the sugars in corn (glucose) has become a major industry in the grain belt. This process can be summarized as follows, where glucose is fermented to form ethanol and carbon dioxide. Use bond energies to estimate $\Delta H$ for this reaction.
$$
\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(s) \longrightarrow 2 \mathrm{CO}_{2}(g)+2 \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(l)
$$
The structure of glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ is

Nicole Smina

Numerade Educator

Problem 123

Most cars in the United States use gasohol for fuel. Gasohol is a mixture consisting of about $10 \%$ ethanol and $90 \%$ gasoline. The enthalpy of combustion per gram of gasoline is $-47.8 \mathrm{~kJ} / \mathrm{g}$. Using the bond energies in Table $8.4$, estimate the enthalpy of combustion per gram of ethanol. How do the two enthalpies of combustion compare with each other? The combustion reaction for ethanol is
$$
\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(l)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)
$$

LJ

Lena Jake

Numerade Educator

Problem 124

Calcium carbonate $\left(\mathrm{CaCO}_{3}\right)$ shells are used by many different types of animals to form protective coverings (including mollusks and bivalves, corals, and snails). Draw the Lewis structures for $\mathrm{CaCO}_{3} .$ Be sure to include formal charges and any important resonance structures.

LJ

Lena Jake

Numerade Educator

Problem 125

Peroxyacetyl nitrate, or PAN, is present in photochemical smog. Draw Lewis structures (including resonance forms) for PAN. The skeletal arrangement is

Vishal Sharma

Numerade Educator

Problem 126

Cholesterol $\left(\mathrm{C}_{27} \mathrm{H}_{46} \mathrm{O}\right)$ has the following structure:
In such shorthand structures, each point where lines meet represents a carbon atom, and most $\mathrm{H}$ atoms are not shown. Draw the complete structure showing all carbon and hydrogen atoms. (There will be four bonds to each carbon atom.) What are the predicted bond angles exhibited in cholesterol? Is cholesterol a planar molecule as indicated in the structure above?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 127

The study of carbon-containing compounds and their properties is called organic chemistry. Besides carbon atoms, organic compounds also can contain hydrogen, oxygen, and nitrogen atoms (as well as other types of atoms). A common trait of simple organic compounds is to have Lewis structures where all atoms have a formal charge of zero. Consider the following incomplete Lewis structure for an organic compound called histidine (an amino acid), which is one of the building blocks of proteins found in our bodies:
Draw a complete Lewis structure for histidine in which all atoms have a formal charge of zero. What should be the approximate bond angles about the carbon atom labeled 1 and the nitrogen atom labeled 2 ?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 128

Benzoic acid is a food preservative. The space-filling model for benzoic acid is shown below.
Draw the Lewis structure for benzoic acid, including all resonance structures in which all atoms have a formal charge of zero. What are the bond angles exhibited in benzoic acid? Is benzoic acid a polar or a nonpolar substance? Explain.

LJ

Lena Jake

Numerade Educator

Problem 129

Arrange the following in order of increasing radius and increasing ionization energy.
a. $\mathrm{N}^{+}, \mathrm{N}, \mathrm{N}^{-}$
b. Se, $\mathrm{Se}^{-}, \mathrm{Cl}, \mathrm{Cl}^{+}$
c. $\mathrm{Br}^{-}, \mathrm{Rb}^{+}, \mathrm{Sr}^{2+}$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 130

For each of the following, write an equation that corresponds to the energy given.
a. lattice energy of $\mathrm{NaCl}$
b. lattice energy of $\mathrm{NH}_{4} \mathrm{Br}$
c. lattice energy of $\mathrm{MgS}$
d. $\mathrm{O}=\mathrm{O}$ double bond energy beginning with $\mathrm{O}_{2}(g)$ as a reactant

LJ

Lena Jake

Numerade Educator

Problem 131

Use bond energies (Table 8.4), values of electron affinities (Table $7.7$ ), and the ionization energy of hydrogen (1312 kJ/mol) to estimate $\Delta H$ for each of the following reactions.
a. $\mathrm{HF}(g) \rightarrow \mathrm{H}^{+}(g)+\mathrm{F}^{-}(g)$
b. $\mathrm{HCl}(g) \rightarrow \mathrm{H}^{+}(g)+\mathrm{Cl}^{-}(g)$
c. $\mathrm{HI}(g) \rightarrow \mathrm{H}^{+}(g)+\mathrm{I}^{-}(g)$
d. $\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{H}^{+}(g)+\mathrm{OH}^{-}(g)$
(Electron affinity of $\mathrm{OH}(g)=-180 . \mathrm{kJ} / \mathrm{mol}$.)

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 132

Write Lewis structures for $\mathrm{CO}_{3}^{2-}, \mathrm{HCO}_{3}^{-}$, and $\mathrm{H}_{2} \mathrm{CO}_{3}$. When acid is added to an aqueous solution containing carbonate or bicarbonate ions, carbon dioxide gas is formed. We generally say that carbonic acid $\left(\mathrm{H}_{2} \mathrm{CO}_{3}\right)$ is unstable. Use bond energies to estimate $\Delta H$ for the reaction (in the gas phase)
$$
\mathrm{H}_{2} \mathrm{CO}_{3} \longrightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}
$$
Specify a possible cause for the instability of carbonic acid.

Lottie Adams

Numerade Educator

Problem 133

Which member of the following pairs would you expect to be more energetically stable? Justify each choice.
a. $\mathrm{NaBr}$ or $\mathrm{NaBr}_{2}$
b. $\mathrm{ClO}_{4}$ or $\mathrm{ClO}_{4}$
c. $\mathrm{SO}_{4}$ or $\mathrm{XeO}_{4}$
d. $\mathrm{OF}_{4}$ or $\mathrm{SeF}_{4}$

Anand Jangid

Numerade Educator

Problem 134

What do each of the following sets of compounds/ions have in common with each other?
a. $\mathrm{SO}_{3}, \mathrm{NO}_{3}^{-}, \mathrm{CO}_{3}^{2-}$
b. $\mathrm{O}_{3}, \mathrm{SO}_{2}, \mathrm{NO}_{2}^{-}$

LJ

Lena Jake

Numerade Educator

Problem 135

What do each of the following sets of compounds/ions have in common with each other? See your Lewis structures for Exercises 107 through 110 .
a. $\mathrm{XeCl}_{4}, \mathrm{XeCl}_{2}$
b. $\mathrm{ICl}_{5}, \mathrm{TeF}_{4}, \mathrm{ICl}_{3}, \mathrm{PCl}_{3}, \mathrm{SCl}_{2}, \mathrm{SeO}_{2}$

Nicole Mabante

Numerade Educator

Problem 136

Although both $\mathrm{Br}_{3}^{-}$ and $\mathrm{I}_{3}^{-}$ ions are known, the $\mathrm{F}_{3}^{-}$ ion has not been observed. Explain.

LJ

Lena Jake

Numerade Educator

Problem 137

Refer back to Exercises 97 and 98 . Would you make the same prediction for the molecular structure for each case using the Lewis structure obtained in Exercise 97 as compared with the one obtained in Exercise 98 ?

Lottie Adams

Numerade Educator

Problem 138

Which of the following molecules have net dipole moments? For the molecules that are polar, indicate the polarity of each bond and the direction of the net dipole moment of the molecule.
a. $\mathrm{CH}_{2} \mathrm{Cl}_{2}, \mathrm{CHCl}_{3}, \mathrm{CCl}_{4}$
b. $\mathrm{CO}_{2}, \mathrm{~N}_{2} \mathrm{O}$
c. $\mathrm{PH}_{3}, \mathrm{NH}_{3}$

LJ

Lena Jake

Numerade Educator

Problem 139

The structure of $\mathrm{TeF}_{5}^{-}$ is
Draw a complete Lewis structure for $\mathrm{TeF}_{5}^{-}$, and explain the distortion from the ideal square pyramidal structure. (See Exercise 106.)

Lottie Adams

Numerade Educator

Problem 140

Look up the energies for the bonds in $\mathrm{CO}$ and $\mathrm{N}_{2}$. Although the bond in $\mathrm{CO}$ is stronger, $\mathrm{CO}$ is considerably more reactive than $\mathrm{N}_{2}$. Give a possible explanation.

LJ

Lena Jake

Numerade Educator

Problem 141

Use Coulomb's law,
$$
V=\frac{Q_{1} Q_{2}}{4 \pi \varepsilon_{0} r}=2.31 \times 10^{-19} \mathrm{~J} \cdot \mathrm{nm}\left(\frac{Q_{1} Q_{2}}{r}\right)
$$
to calculate the energy of interaction for the following two arrangements of charges, each having a magnitude equal to the electron charge.

Ronald Prasad

Numerade Educator

Problem 142

An alternative definition of electronegativity is
Electronegativity $=$ constant (I.E. $-$ E.A.)
where I.E. is the ionization energy and E.A. is the electron affinity using the sign conventions of this book. Use data in Chapter 7 to calculate the (I.E. $-$ E.A.) term for $\mathrm{F}, \mathrm{Cl}, \mathrm{Br}$, and $\mathrm{I}$. Do these values show the same trend as the electronegativity values given in this chapter? The first ionization energies of the halogens are $1678,1255,1138$, and $1007 \mathrm{~kJ} / \mathrm{mol}$, respectively. (Hint: Choose a constant so that the electronegativity of fluorine equals 4.0. Using this constant, calculate relative electronegativities for the other halogens and compare to values given in the text.)

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 143

Calculate the standard heat of formation of the compound $\mathrm{ICl}(g)$ at $25^{\circ} \mathrm{C}$, and show your work. (Hint: Use Table $8.4$ and Appendix 4.)

Julian Taurozzi

Julian Taurozzi

Numerade Educator

Problem 144

Given the following information:
Heat of sublimation of $\operatorname{Li}(s)=166 \mathrm{~kJ} / \mathrm{mol}$
Bond energy of $\mathrm{HCl}=427 \mathrm{~kJ} / \mathrm{mol}$
Ionization energy of $\operatorname{Li}(g)=520 . \mathrm{kJ} / \mathrm{mol}$
Electron affinity of $\mathrm{Cl}(g)=-349 \mathrm{~kJ} / \mathrm{mol}$
Lattice energy of $\operatorname{LiCl}(s)=-829 \mathrm{~kJ} / \mathrm{mol}$
Bond energy of $\mathrm{H}_{2}=432 \mathrm{~kJ} / \mathrm{mol}$
Calculate the net change in energy for the following reaction:
$$
2 \mathrm{Li}(s)+2 \mathrm{HCl}(g) \longrightarrow 2 \mathrm{LiCl}(s)+\mathrm{H}_{2}(g)
$$

LJ

Lena Jake

Numerade Educator

Problem 145

Use data in this chapter (and Chapter 7) to discuss why $\mathrm{MgO}$ is an ionic compound but $\mathrm{CO}$ is not an ionic compound.

Ronald Prasad

Numerade Educator

Problem 146

Think of forming an ionic compound as three steps (this is a simplification, as with all models): (1) removing an electron from the metal; (2) adding an electron to the nonmetal; and (3) allowing the metal cation and nonmetal anion to come together.
a. What is the sign of the energy change for each of these three processes?
b. In general, what is the sign of the sum of the first two processes? Use examples to support your answer.
c. What must be the sign of the sum of the three processes?
d. Given your answer to part $\mathrm{c}$, why do ionic bonds occur?
e. Given your above explanations, why is NaCl stable but not $\mathrm{Na}_{2} \mathrm{Cl} ? \mathrm{NaCl}_{2} ?$ What about $\mathrm{MgO}$ compared to $\mathrm{MgO}_{2} ?$
$\mathrm{Mg}_{2} \mathrm{O} ?$

LJ

Lena Jake

Numerade Educator

Problem 147

The compound $\mathrm{NF}_{3}$ is quite stable, but $\mathrm{NCl}_{3}$ is very unstable $\left(\mathrm{NCl}_{3}\right.$ was first synthesized in 1811 by $\mathrm{P}$. $\mathrm{L}$. Dulong, who lost three fingers and an eye studying its properties). The compounds $\mathrm{NBr}_{3}$ and $\mathrm{NI}_{3}$ are unknown, although the explosive compound $\mathrm{NI}_{3} \cdot \mathrm{NH}_{3}$ is known. Account for the instability of these halides of nitrogen.

Lottie Adams

Numerade Educator

Problem 148

Three processes that have been used for the industrial manufacture of acrylonitrile $\left(\mathrm{CH}_{2} \mathrm{CHCN}\right)$, an important chemical used in the manufacture of plastics, synthetic rubber, and fibers, are
shown below. Use bond energy values (Table 8.4) to estimate $\Delta H$ for each of the reactions.

LJ

Lena Jake

Numerade Educator

Problem 149

The compound hexaazaisowurtzitane is the highest-energy explosive known ( $C$ \& $E$ News, Jan. 17,1994, p. 26 ). The compound, also known as CL-20, was first synthesized in 1987 . The method of synthesis and detailed performance data are still classified because of CL-20's potential military application in rocket boosters and in warheads of "smart" weapons. The structure of CL-20 is
In such shorthand structures, each point where lines meet represents a carbon atom. In addition, the hydrogens attached to the carbon atoms are omitted; each of the six carbon atoms has one hydrogen atom attached. Finally, assume that the two $\mathrm{O}$ atoms in the $\mathrm{NO}_{2}$ groups are attached to $\mathrm{N}$ with one single bond and one double bond.

Three possible reactions for the explosive decomposition of CL-20 are
i. $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{~N}_{12} \mathrm{O}_{12}(s) \rightarrow 6 \mathrm{CO}(g)+6 \mathrm{~N}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)+\frac{3}{2} \mathrm{O}_{2}(g)$
ii. $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{~N}_{12} \mathrm{O}_{12}(s) \rightarrow 3 \mathrm{CO}(\mathrm{g})+3 \mathrm{CO}_{2}(g)+6 \mathrm{~N}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)$
iii. $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{~N}_{12} \mathrm{O}_{12}(s) \rightarrow 6 \mathrm{CO}_{2}(g)+6 \mathrm{~N}_{2}(g)+3 \mathrm{H}_{2}(g)$
a. Use bond energies to estimate $\Delta H$ for these three reactions.
b. Which of the above reactions releases the largest amount of energy per kilogram of CL-20?

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 150

Many times extra stability is characteristic of a molecule or ion in which resonance is possible. How could this be used to explain the acidities of the following compounds? (The acidic hydrogen is marked by an asterisk.) Part c shows resonance in the $\mathrm{C}_{6} \mathrm{H}_{5}$ ring.

LJ

Lena Jake

Numerade Educator

Problem 151

A common trait of simple organic compounds is to have Lewis structures where all atoms have a formal charge of zero. Consider the following incomplete Lewis structure for an organic compound called methyl cyanoacrylate, the main ingredient in Super Glue.
Draw a complete Lewis structure for methyl cyanoacrylate in which all atoms have a formal charge of zero. What are the approximate bond angles about the carbon atom labeled 1, the carbon atom labeled 2, and the oxygen atom labeled $3 ?$

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 152

Draw a Lewis structure for the $N, N$ -dimethylformamide molecule. The skeletal structure is
Various types of evidence lead to the conclusion that there is some double bond character to the $\mathrm{C}-\mathrm{N}$ bond. Draw one or more resonance structures that support this observation.

LJ

Lena Jake

Numerade Educator

Problem 153

Predict the molecular structure for each of the following. (See Exercises 105 and $106 .$ )
a. $\mathrm{BrFI}_{2}$
b. $\mathrm{XeO}_{2} \mathrm{~F}_{2}$
c. $\mathrm{TeF}_{2} \mathrm{Cl}_{3}^{-}$
For each formula there are at least two different structures that can be drawn using the same central atom. Draw all possible structures for each formula.

Brooke Smith

Numerade Educator

Problem 154

Consider the following computer-generated model of caffeine.
Draw a Lewis structure for caffeine in which all atoms have a formal charge of zero.

LJ

Lena Jake

Numerade Educator

Problem 155

A compound, $\mathrm{XF}_{5}$, is $42.81 \%$ fluorine by mass. Identify the element $X$. What is the molecular structure of $\mathrm{XF}_{5}$ ?

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 156

A polyatomic ion is composed of $\mathrm{C}, \mathrm{N}$, and an unknown element $\mathrm{X} .$ The skeletal Lewis structure of this polyatomic ion is $[\mathrm{X}-\mathrm{C}-\mathrm{N}]^{-} .$ The ion $\mathrm{X}^{2-}$ has an electron configuration of $[\mathrm{Ar}] 4 s^{2} 3 d^{10} 4 p^{6} .$ What is element $\mathrm{X} ?$ Knowing the identity of $\mathrm{X}$, complete the Lewis structure of the polyatomic ion, including all important resonance structures.

LJ

Lena Jake

Numerade Educator

Problem 157

Identify the following elements based on their electron configurations and rank them in order of increasing electronegativity:
$[\mathrm{Ar}] 4 s^{1} 3 d^{5} ;[\mathrm{Ne}] 3 s^{2} 3 p^{3} ;[\mathrm{Ar}] 4 s^{2} 3 d^{10} 4 p^{3} ;[\mathrm{Ne}] 3 s^{2} 3 p^{5}$.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 158

Identify the five compounds of $\mathrm{H}, \mathrm{N}$, and $\mathrm{O}$ described below. For each compound, write a Lewis structure that is consistent with the information given.
a. All the compounds are electrolytes, although not all of them are strong electrolytes. Compounds $\mathrm{C}$ and $\mathrm{D}$ are ionic and compound $\mathrm{B}$ is covalent.
b. Nitrogen occurs in its highest possible oxidation state in compounds $\mathrm{A}$ and $\mathrm{C}$; nitrogen occurs in its lowest possible oxidation state in compounds $\mathrm{C}, \mathrm{D}$, and $\mathrm{E}$. The formal charge on both nitrogens in compound $\mathrm{C}$ is $+1$; the formal charge on the only nitrogen in compound $\mathrm{B}$ is $0 .$
c. Compounds A and E exist in solution. Both solutions give off gases. Commercially available concentrated solutions of compound $\mathrm{A}$ are normally $16 M .$ The commercial, concentrated solution of compound $\mathrm{E}$ is $15 M$.
d. Commercial solutions of compound $\mathrm{E}$ are labeled with a misnomer that implies that a binary, gaseous compound of nitrogen and hydrogen has reacted with water to produce ammonium ions and hydroxide ions. Actually, this reaction occurs to only a slight extent.
e. Compound $\mathrm{D}$ is $43.7 \% \mathrm{~N}$ and $50.0 \% \mathrm{O}$ by mass. If compound D were a gas at STP, it would have a density of $2.86 \mathrm{~g} / \mathrm{L}$.
f. A formula unit of compound $\mathrm{C}$ has one more oxygen than a formula unit of compound D. Compounds $\mathrm{C}$ and $\mathrm{A}$ have one ion in common when compound $\mathrm{A}$ is acting as a strong electrolyte.
g. Solutions of compound $\mathrm{C}$ are weakly acidic; solutions of compound $\mathrm{A}$ are strongly acidic; solutions of compounds $\mathrm{B}$ and $\mathrm{E}$ are basic. The titration of $0.726 \mathrm{~g}$ compound $\mathrm{B}$ requires $21.98 \mathrm{~mL}$ of $1.000 M \mathrm{HCl}$ for complete neutralization.

Susan Hallstrom

Susan Hallstrom

Numerade Educator