Chemical Principle

Steven S. Zumdahl, Donald J. DeCoste

Chapter 13

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 energy and atomic radii. How are they all related?

Lottie Adams

Lottie Adams

Numerade Educator

Problem 2

The ionic compound 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 Ga. Arrange these from largest to smallest radius, and explain why the radius varies as it does. Compare your predictions with Fig. 13.8

Lottie Adams

Numerade Educator

Problem 4

The bond energy for the $\mathrm{C}-\mathrm{H}$ 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 $\mathrm{C}-\mathrm{H}$ bond energy in $\mathrm{CHBr}_{3}$ is lower make any sense? Why?

LJ

Lena Jake

Numerade Educator

Problem 5

Consider the following statement: "Because oxygen seems to prefer 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 information, and explain.

Lottie Adams

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

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 11

Distinguish between the terms electronegativity and elec tron affinity, covalent bond and ionic bond, and pure covalent bond and polar covalent bond. Characterize the types of bonds in terms of electronegativity difference. Energetically, why do ionic and covalent bonds form?

Lottie Adams

Numerade Educator

Problem 12

The following electrostatic potential diagrams represent $\mathrm{H}_{2}, \mathrm{HCl},$ or $\mathrm{NaCl} .$ Label each, and explain your choices.
(FIGURE CANNOT COPY)

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 13

An alternative definition of electronegativity is
Electronegativity $=\text { constant (I.E. }-\text { E.A. })$
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 12 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.)

Lottie Adams

Numerade Educator

Problem 14

Use Coulomb's law,
$$
V=\frac{Q_{1} Q_{2}}{4 \pi \epsilon_{0} r}=2.31 \times 10^{-19} \mathrm{J} \mathrm{nm}\left(\frac{Q_{1} Q_{2}}{r}\right)
$$
to calculate the energy of interaction for the following two arrangements of charges, each having a magnitude equal to the electron charge.
(EQUATION CANNOT COPY)

Ronald Prasad

Numerade Educator

Problem 15

Without using Fig. $13.3,$ predict the order of increasing electronegativity in each of the following groups of elements.
a. $\mathrm{C}, \mathrm{N}, \mathrm{O}$
b. $\mathrm{S}, \mathrm{Se}, \mathrm{Cl}$
c. $\mathrm{Si}, \mathrm{Ge}, \mathrm{Sn}$
d. $\mathrm{Tl}, \mathrm{S}, \mathrm{Ge}$
e. $\mathrm{Na}, \mathrm{K}, \mathrm{Rb}$
f. $\mathrm{B}, \mathrm{O}, \mathrm{Ga}$

Lottie Adams

Numerade Educator

Problem 16

Without using Fig. $13.3,$ predict which bond in each of the following groups is the most polar.
a. $\mathrm{C}-\mathrm{F}, \mathrm{Si}-\mathrm{F}, \mathrm{Ge}-\mathrm{F}$
b. $\mathrm{P}-\mathrm{Cl}, \mathrm{S}-\mathrm{Cl}$
c. $\mathrm{S}-\mathrm{F}, \mathrm{S}-\mathrm{Cl}, \mathrm{S}-\mathrm{Br}$
d. $\mathrm{Ti}-\mathrm{Cl}, \mathrm{Si}-\mathrm{Cl}, \mathrm{Ge}-\mathrm{Cl}$
e. $\mathrm{C}-\mathrm{H}, \mathrm{Si}-\mathrm{H}, \mathrm{Sn}-\mathrm{H}$
f. $\mathrm{Al}-\mathrm{Br}, \mathrm{Ga}-\mathrm{Br}, \mathrm{In}-\mathrm{Br}, \mathrm{Tl}-\mathrm{Br}$

Lottie Adams

Numerade Educator

Problem 17

Repeat Exercises 15 and $16 .$ This time use the values of the electronegativities of the elements given in Fig. 13.3 Are there any differences among your answers?

Lottie Adams

Numerade Educator

Problem 18

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 19

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 20

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 21

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 22

The following electrostatic potential diagrams represent $\mathrm{CH}_{4}, \mathrm{NH}_{3},$ or $\mathrm{H}_{2} \mathrm{O} .$ Label each, and explain your choices.
(FIGURE CANNOT COPY)

LJ

Lena Jake

Numerade Educator

Problem 23

When an element forms an anion, what happens to the radius? When an element forms a cation, what happens to the radius? Why? Define the term isoelectronic. When comparing sizes of ions, which ion has the largest radius, and which ion has the smallest radius in an isoelectronic series? Why?

Lottie Adams

Numerade Educator

Problem 24

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.
(FIGURE CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 25

For each of the following groups, place the atoms and 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. $\mathrm{Te}^{2-}, \mathrm{I}^{-}, \mathrm{Cs}^{+}, \mathrm{Ba}^{2+}, \mathrm{La}^{3+}$

Lottie Adams

Numerade Educator

Problem 26

Write electron configurations for each of the following.
a. the cations: $\mathrm{Mg}^{2+}, \mathrm{Sn}^{2+}, \mathrm{K}^{+}, \mathrm{Al}^{3+}, \mathrm{Tl}^{+}, \mathrm{As}^{3+}$
b. the anions: $\mathrm{N}^{3-}, \mathrm{O}^{2-}, \mathrm{F}^{-}, \mathrm{Te}^{2-}$

Lottie Adams

Numerade Educator

Problem 27

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

Lottie Adams

Numerade Educator

Problem 28

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

LJ

Lena Jake

Numerade Educator

Problem 29

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

Bryan Li

Numerade Educator

Problem 30

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 31

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

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 32

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. $\mathrm{NaBr}, \mathrm{NaI}$
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 33

Predict the empirical formulas of the ionic compounds formed from the following pairs of elements. Name each compound.
a. $\mathrm{Al}$ and $\mathrm{S}$
b. $\mathrm{K}$ and $\mathrm{N}$
c. $\mathrm{Mg}$ and $\mathrm{Cl}$
d. $\mathrm{Cs}$ and $\mathrm{Br}$

Lottie Adams

Numerade Educator

Problem 34

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

Lottie Adams

Numerade Educator

Problem 35

Use the following data to estimate $\Delta H_{\mathrm{f}}^{\circ}$ for potassium chloride.
$$
\mathrm{K}(s)+\frac{1}{2} \mathrm{Cl}_{2}(g) \longrightarrow \mathrm{KCl}(s)
$$
(TABLE CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 36

Use the following data to estimate $\Delta H_{\mathrm{f}}^{\circ}$ for magnesium fluoride.
$$
\mathrm{Mg}(s)+\mathrm{F}_{2}(g) \longrightarrow \mathrm{MgF}_{2}(s)
$$
(TABLE CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 37

Consider the following: $\operatorname{Li}(s)+\frac{1}{2} \mathrm{I}_{2}(g) \rightarrow \operatorname{LiI}(s) \Delta H=$$-292 \mathrm{kJ} .$ LiI(s) has a lattice energy of $-753 \mathrm{kJ} / \mathrm{mol} .$ The ionization energy of $\operatorname{Li}(g)$ 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 Li(s).

Lottie Adams

Numerade Educator

Problem 38

In general, the higher the charge on the ions in an ionic compound, the more favorable is 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 39

Consider the following energy changes:
(TABLE CANNOT COPY)
a. Magnesium oxide exists as $\mathrm{Mg}^{2+} \mathrm{O}^{2-},$ not as $\mathrm{Mg}^{+} \mathrm{O}^{-} .$ Explain.
b. What experiment could be done to confirm that magnesium oxide does not exist as $\mathrm{Mg}^{+} \mathrm{O}^{-} ?$

Lottie Adams

Numerade Educator

Problem 40

Use the following data (in $\mathrm{kJ} / \mathrm{mol}$ ) to estimate $\Delta H$ for the reaction $\mathrm{S}^{-}(g)+\mathrm{e}^{-} \rightarrow \mathrm{S}^{2-}(g) .$ Include an estimate of uncertainty.
(TABLE CANNOT COPY)
$S(s) \longrightarrow S(g) \quad \Delta H=277 \mathrm{kJ} / / \mathrm{mol}$
$\mathrm{S}(g)+\mathrm{e}^{-} \longrightarrow \mathrm{S}^{-}(g) \quad \Delta H=-200 . \mathrm{kJ} / \mathrm{mol}$

David Collins

Numerade Educator

Problem 41

Rationalize the following lattice energy values:
(TABLE CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 42

The lattice energies of $\mathrm{FeCl}_{3}, \mathrm{FeCl}_{2},$ and $\mathrm{Fe}_{2} \mathrm{O}_{3}$ are (in no particular order) $-2631 \mathrm{kJ} / \mathrm{mol},-5339 \mathrm{kJ} / \mathrm{mol},$ and
$-14,774 \mathrm{kJ} / \mathrm{mol} .$ Match the appropriate formula to each lattice energy.

Lottie Adams

Numerade Educator

Problem 43

Use bond energy values in Table 13.6 to estimate $\Delta H$ for each of the following reactions in the gas phase.
a. $\mathrm{H}_{2}(g)+\mathrm{Cl}_{2}(g) \rightarrow 2 \mathrm{HCl}(g)$
b. $\mathrm{N} \equiv \mathrm{N}(g)+3 \mathrm{H}_{2}(g) \rightarrow 2 \mathrm{NH}_{3}(g)$
c. (EQUATION CANNOT COPY)
d. (EQUATION CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 44

Compare your answers from parts a and b of Exercise 43 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 45

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

Lottie Adams

Numerade Educator

Problem 46

Use data from Table 13.6 to estimate $\Delta H$ for the combustion of methane $\left(\mathrm{CH}_{4}\right),$ as shown below:
(FIGURE CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 47

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

Lottie Adams

Numerade Educator

Problem 48

Consider the following reaction:
$$
\mathrm{A}_{2}+\mathrm{B}_{2} \longrightarrow 2 \mathrm{AB} \quad \Delta H=-285 \mathrm{kJ}
$$
The bond energy for $A_{2}$ is one-half the amount of the 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 49

The space shuttle orbiter uses 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
(EQUATION CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 50

Following are three processes that have been used for the industrial manufacture of acrylonitrile-an important chemical used in the manufacture of plastics, synthetic rubber, and fibers. Use bond energy values (Tables 13.6 and 13.7 ) to estimate $\Delta H$ for each of the reactions.
(EQUATION CANNOT COPY)

LJ

Lena Jake

Numerade Educator

Problem 51

Is the elevated temperature noted in parts $\mathrm{b}$ and $\mathrm{c}$ of Exercise 50 needed to provide energy to endothermic reactions?

Lottie Adams

Numerade Educator

Problem 52

Acetic acid is responsible for the sour taste of vinegar. It can be manufactured using the following reaction:
(EQUATION CANNOT COPY)
Use tabulated values of bond energies (Table 13.6 ) to estimate $\Delta H$ for this reaction. Compare this result to the $\Delta H$ value calculated using standard enthalpies of formation in Appendix 4. Explain any discrepancies.

Lottie Adams

Numerade Educator

Problem 53

Use bond energies (Table $13.6),$ values of electron affinities (Table $12.8),$ and the ionization energy of hydrogen $(1312 \mathrm{kJ} / \mathrm{mol})$ to estimate $\Delta H$ for each of the following reactions.
a. $\mathrm{HF}(g) \longrightarrow \mathrm{H}^{+}(g)+\mathrm{F}^{-}(g)$
b. $\mathrm{HCl}(g) \longrightarrow \mathrm{H}^{+}(g)+\mathrm{Cl}^{-}(g)$
c. $\mathrm{HI}(g) \longrightarrow \mathrm{H}^{+}(g)+\mathrm{I}^{-}(g)$
d. $\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow \mathrm{H}^{+}(g)+\mathrm{OH}^{-}(g)$
(Electron affinity of $\mathrm{OH}(g)=-180 . \mathrm{kJ} / \mathrm{mol} .$ )

Lottie Adams

Numerade Educator

Problem 54

The standard enthalpies of formation of $S(g), \quad F(g)$ $\mathrm{SF}_{4}(g),$ and $\mathrm{SF}_{6}(g)$ are $+278.8 \mathrm{kJ} / \mathrm{mol},+79.0 \mathrm{kJ} / \mathrm{mol}$
$-775 \mathrm{kJ} / \mathrm{mol},$ and $-1209 \mathrm{kJ} / \mathrm{mol},$ respectively.
a. Use these data to estimate the energy of an $\mathrm{S}-\mathrm{F}$ bond.
b. Compare the value that you calculated in part a with the value given in Table $13.6 .$ What conclusions can you draw?
c. Why are the $\Delta H_{i}^{\circ}$ values for $S(g)$ and $\mathrm{F}(g)$ not equal to zero, even though sulfur and fluorine are elements?

Lottie Adams

Numerade Educator

Problem 55

Use the following standard enthalpies of formation to estimate the $\mathrm{N}-\mathrm{H}$ bond energy in ammonia. Compare this with the value in Table 13.6
$$\begin{aligned}
&\mathrm{N}(g) \quad 472.7 \mathrm{k} J / \mathrm{mol}\\
&\mathrm{H}(g) \quad 216.0 \mathrm{kJ} / \mathrm{mol}\\
&\mathrm{NH}_{3}(g) \quad-46.1 \mathrm{kJ} / \mathrm{mol}
\end{aligned}$$

Lottie Adams

Numerade Educator

Problem 56

The standard enthalpy of formation for $\mathrm{NO}(g)$ is $90 . \mathrm{kJ} /$ 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 57

Write Lewis structures that obey the octet rule for each of the following. Except for HCN and $\mathrm{H}_{2} \mathrm{CO},$ the first atom listed is the central atom. For HCN and $\mathrm{H}_{2} \mathrm{CO}$ carbon is the central atom.
a. $\mathrm{HCN}$
b. $\mathrm{PH}_{3}$
c. $\mathrm{CHCl}_{3}$
d. $\mathrm{NH}_{4}^{+}$
e. $\mathrm{H}_{2} \mathrm{CO}$
f. $\operatorname{SeF}_{2}$
g. $\mathrm{CO}_{2}$
h. $\mathrm{O}_{2}$
i. $\mathrm{HBr}$

Lottie Adams

Numerade Educator

Problem 58

Draw a Lewis structure that obeys 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. $\mathrm{ClO}_{2}^{-}, \mathrm{SCl}_{2}, \mathrm{PCl}_{2}$

Lottie Adams

Numerade Educator

Problem 59

Considering your answers to Exercise $58,$ what conclusions can you draw concerning the structures of species containing the same number of atoms and the same number of valence electrons?

Lottie Adams

Numerade Educator

Problem 60

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

Lottie Adams

Numerade Educator

Problem 61

Some of the pollutants in the atmosphere are ozone, sulfur dioxide, and sulfur trioxide. Draw Lewis structures for these three molecules. Show all resonance structures.

Lottie Adams

Numerade Educator

Problem 62

Peroxyacetyl nitrate, or PAN, is present in photochemical smog. Draw Lewis structures (including resonance forms) for PAN. The skeletal arrangement is
(EQUATION CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 63

A toxic cloud covered Bhopal, India, in December 1984 when water leaked into a tank of methyl isocyanate, and the product escaped into the atmosphere. Methyl isocyanate is used in the production of many pesticides. Draw the Lewis structures for methyl isocyanate, $\mathrm{CH}_{3} \mathrm{NCO}$ including resonance forms.

Lottie Adams

Numerade Educator

Problem 64

Explain the terms resonance and delocalized electrons. When a substance exhibits resonance, we say that none of the individual Lewis structures accurately portrays the bonding in the substance. Why do we draw resonance structures?

Lottie Adams

Numerade Educator

Problem 65

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. Draw Lewis structures for benzene, including resonance structures.

Lottie Adams

Numerade Educator

Problem 66

An important observation supporting the need for resonance in the LE model is 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 need for the concept of resonance?

Lottie Adams

Numerade Educator

Problem 67

Borazine $\left(\mathrm{B}_{3} \mathrm{N}_{3} \mathrm{H}_{6}\right)$ has often been called "inorganic" benzene. Draw Lewis structures for borazine. Borazine is a six-membered ring of alternating boron and nitrogen atoms.

Lottie Adams

Numerade Educator

Problem 68

Draw all the possible Lewis structures for dimethylborazine $\left[\left(\mathrm{CH}_{3}\right)_{2} \mathrm{B}_{3} \mathrm{N}_{3} \mathrm{H}_{4}\right] .$ (See Exercise $67 .$ ) Would there be a different number of structures if there was no resonance?

Lottie Adams

Numerade Educator

Problem 69

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 oxygen-oxygen bond.

Lottie Adams

Numerade Educator

Problem 70

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 71

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 structures for these compounds or ions. Which elements, when they have to, can have more than eight electrons around them? How is this rationalized?

Lottie Adams

Numerade Educator

Problem 72

$\mathrm{SF}_{6}, \mathrm{ClF}_{5},$ 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 73

Consider the following bond lengths:
(EQUATION CANNOT COPY)
In the $\mathrm{CO}_{3}^{2-}$ ion, all three $\mathrm{C}-\mathrm{O}$ bonds have identical bond lengths of $1.36 \AA .$ Why?

Lottie Adams

Numerade Educator

Problem 74

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

Lottie Adams

Numerade Educator

Problem 75

Place the species below in order of the shortest to the longest nitrogen-oxygen bond.
(EQUATION CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 76

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 77

Use formal charge arguments to explain why 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 78

Nitrous oxide $\left(\mathrm{N}_{2} \mathrm{O}\right)$ has three possible Lewis structures:
(EQUATION CANNOT COPY)
Given the following bond lengths,
(EQUATION CANNOT COPY)
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 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?

Lottie Adams

Numerade Educator

Problem 79

Draw Lewis structures that obey the octet rule for the following species. Assign the formal charge to each central atom.
a. $\mathrm{POCl}_{3}$
b. $\mathrm{SO}_4{^2}{^-}$
c. $\mathrm{ClO}$${4}^{-}$
d. $\mathrm{PO}_{4}{^3}{^-}$
e. $\mathrm{SO}_{2} \mathrm{Cl}_{2}$
f. $\mathrm{XeO}_{4}$
g. $\mathrm{ClO}$$3^{-}$
h. $$\mathrm{NO}_{4}{^3}{^-}$$

Lottie Adams

Numerade Educator

Problem 80

Draw the Lewis structures that involve minimum formal charges for the species in Exercise $79 .$

Lottie Adams

Numerade Educator

Problem 81

When molten sulfur reacts with chlorine gas, a vilesmelling 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 vile-smelling orange liquid.

Lottie Adams

Numerade Educator

Problem 82

Oxidation of the cyanide ion produces the stable cyanate ion $\left(\mathrm{OCN}^{-}\right) .$ The fulminate ion $\left(\mathrm{CNO}^{-}\right),$ on the other hand, is very unstable. Fulminate salts explode when struck; Hg(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 83

Write the Lewis Structure for $\mathrm{O}_{2} \mathrm{F}_{2}$ ( $\mathrm{O}_{2} \mathrm{F}_{2}$ exists as $\mathrm{F}-\mathrm{O}-\mathrm{O}-\mathrm{F}$) 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 84

Benzoic acid is a food preservative. The space-filling model for benzoic acid is shown below.
(FIGURE CANNOT COPY)
Draw the Lewis structure for benzoic acid, including all resonance structures in which all atoms have a formal charge of zero.

LJ

Lena Jake

Numerade Educator

Problem 85

Write the name of each of the following molecular structures.
(FIGURE CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 86

State whether or not each of the following has a permanent dipole moment.
(FIGURE CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 87

Predict the molecular structure and the bond angles for each molecule or ion in Exercises $57,58,$ and $60 .$

Lottie Adams

Numerade Educator

Problem 88

Predict the molecular structure and the bond angles for each of the following.
a. $\mathrm{SeO}_{3}$
b. $\mathrm{SeO}_{2}$
c. $\mathrm{PCl}_{3}$
d. $\mathrm{SCl}_{2}$
e. $\mathrm{SiF}_{4}$

Lottie Adams

Numerade Educator

Problem 89

There are several molecular structures based on the trigonal bipyramid geometry. Three such structures are
(EQUATION CANNOT COPY)
Which of the compounds or ions in Exercises 71 and 72 have these molecular structures?

Lottie Adams

Numerade Educator

Problem 90

Two variations of the octahedral geometry are illustrated below.
(FIGURE CANNOT COPY)
Which of the compounds or ions in Exercises 71 and 72 have these molecular structures?

Lottie Adams

Numerade Educator

Problem 91

Predict the molecular structure and the bond angles for each of the following. (See Exercises 89 and $90 .$ )
a. $\mathrm{XeCl}_{2}$
b. ICl $_{3}$
c. TeF $_{4}$
d. $\mathrm{PCl}_{5}$

Lottie Adams

Numerade Educator

Problem 92

Predict the molecular structure and the bond angles for each of the following. (See Exercises 89 and $90 .$ )
a. $\mathrm{ICl}_{5}$
b. $\mathrm{XeCl}_{4}$
c. $\mathrm{SeCl}_{6}$

Lottie Adams

Numerade Educator

Problem 93

Which of the molecules in Exercise 88 have net dipole moments (are polar)?

Lottie Adams

Numerade Educator

Problem 94

Which of the molecules in Exercises 91 and 92 have net dipole moments (are polar)?

Lottie Adams

Numerade Educator

Problem 95

Give two requirements that should be satisfied for a molecule to be polar. Explain why $\mathrm{CF}_{4}$ and $\mathrm{XeF}_{4}$ are nonpolar compounds (have no net dipole moments), whereas $\mathrm{SF}_{4}$ is polar (has a net dipole moment). Is $\mathrm{CO}_{2}$ polar? What about COS? Explain.

Lottie Adams

Numerade Educator

Problem 96

What do each of the following sets of compounds/ions have in common with each other? Reference your Lewis structures for Exercises $88,91,$ and 92
a. $\mathrm{XeCl}_{4}, \mathrm{XeCl}_{2}$
b. $\mathrm{ICl}_{5}, \mathrm{TeF}_{4}, \mathrm{ICl}_{3}, \mathrm{PCl}_{3}, \mathrm{SCl}_{2}, \mathrm{SeO}_{2}$

Lottie Adams

Numerade Educator

Problem 97

Which of the following statements is(are) true? Correct the false statements.
a. The molecules $\operatorname{SeS}_{3}, \operatorname{SeS}_{2}, \mathrm{PCl}_{5}, \mathrm{TeCl}_{4}, \mathrm{ICl}_{3},$ and
$\mathrm{XeCl}_{2}$ all exhibit at least one bond angle which is approximately 120 degrees.
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 98

Consider the following Lewis structure, where $\mathrm{E}$ is an unknown element:
(FIGURE CANNOT COPY)
What are some possible identities for element E? Predict the molecular structure (including bond angles) for this ion.

Lottie Adams

Numerade Educator

Problem 99

Consider the following Lewis structure, where $\mathrm{E}$ is an unknown element:
(FIGURE CANNOT COPY)
What are some possible identities for element E? Predict the molecular structure (including bond angles) for this ion. (See Exercises $89 \text { and } 90 .)$

Lottie Adams

Numerade Educator

Problem 100

Although the VSEPR model is correct in predicting that $\mathrm{CH}_{4}$ is tetrahedral, $\mathrm{NH}_{3}$ is pyramidal, and $\mathrm{H}_{2} \mathrm{O}$ is bent, the model in its simplest form does not account for the fact that these molecules do not have exactly the same bond angles $(<\mathrm{HCH} \text { is } 109.5$ degrees, as expected for a tetrahedron, but $<$ HNH is 107.3 degrees and $<\mathrm{HOH}$ is 104.5 degrees). Explain these deviations from the tetrahedral angle.

Lottie Adams

Numerade Educator

Problem 101

Draw Lewis structures and predict the molecular structures of the following. (See Exercises 89 and $90 .$ )
a. $\mathrm{OCl}_{2}, \mathrm{KrF}_{2}, \mathrm{BeH}_{2}, \mathrm{SO}_{2}$
c. $\mathrm{CF}_{4}, \mathrm{SeF}_{4}, \mathrm{KrF}_{4}$
b. $\mathrm{SO}_{3}, \mathrm{NF}_{3}, \mathrm{IF}_{3}$
d. $\mathrm{IF}_{5}, \mathrm{AsF}_{5}$
Which of the above compounds have net dipole moments (are polar)?

Lottie Adams

Numerade Educator

Problem 102

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. $\mathrm{PH}_{3}, \mathrm{NH}_{3}$

Lottie Adams

Numerade Educator

Problem 103

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

Lottie Adams

Numerade Educator

Problem 104

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

Lottie Adams

Numerade Educator

Problem 105

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 106

The structure of $\mathrm{TeF}_{5}-$ is
(FIGURE CANNOT COPY)
Draw a complete Lewis structure for $\mathrm{TeF}_{5}^{-},$ and explain the distortion from the ideal square pyramidal structure. (See Exercise $90 .)$

Lottie Adams

Numerade Educator

Problem 107

The compound $\mathrm{NF}_{3}$ is quite stable, but $\mathrm{NCl}_{3}$ is very unstable (NCl $_{3}$ was first synthesized in 1811 by P. 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 108

There are two possible structures of $\mathrm{XeF}_{2} \mathrm{Cl}_{2},$ where $\mathrm{Xe}$ is the central atom. Draw them, and describe how measurements of dipole moments might be used to distinguish among them.

Lottie Adams

Numerade Educator

Problem 109

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 $\mathrm{SeF}_{4}$

David Collins

Numerade Educator

Problem 110

Many times, extra stability is characteristic of a molecule or ion in which resonance is possible. How could this feature be used to explain the acidities of the following compounds? (The acidic hydrogen is marked by an asterisk.) Part c shows resonance in the phenyl ring $\left(\mathrm{C}_{6} \mathrm{H}_{5}\right) .$
(EQUATION CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 111

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

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 112

Draw a Lewis structure for the $N, N$ -dimethylformamide molecule. The skeletal structure is
(EQUATION CANNOT COPY)
Various types of evidence lead to the conclusion that there is some double-bond character to one of the $\mathrm{C}-\mathrm{N}$ bonds. Draw one or more resonance structures that support this observation.

Lottie Adams

Numerade Educator

Problem 113

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 114

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 in which all atoms have a formal charge of zero. Consider the following incomplete Lewis structure for an organic compound called histidine (one of the amino acids, which are the building blocks of proteins found in human bodies):
(EQUATION CANNOT COPY)
Draw a complete Lewis structure for histidine in which all atoms have a formal charge of zero. What are the approximate bond angles about the carbon atom labeled 1 and the nitrogen atom labeled $2 ?$

Lottie Adams

Numerade Educator

Problem 115

Do the Lewis structures obtained in Exercises 79 and 80 predict the same molecular structure for each case?

Lottie Adams

Numerade Educator

Problem 116

Predict the molecular structure for each of the following. (See Exercises $89 \text { and } 90 .)$
a. $\mathrm{BrFI}_{2}$
b. $\mathrm{XeO}_{2} \mathrm{F}_{2}$
c. $\mathrm{TeF}_{2} \mathrm{Cl}_{3}{^-}$

Lottie Adams

Numerade Educator

Problem 117

Predict the molecular structure of $\mathrm{KrF}_{2} .$ Using hyperconjugation, draw the Lewis structures for $\mathrm{KrF}_{2}$ that obey the octet rule. Show all resonance forms.

Lottie Adams

Numerade Educator

Problem 118

Consider the following computer-generated model of caffeine.
(FIGURE CANNOT COPY)
Draw a Lewis structure for caffeine in which all atoms have a formal charge of zero.

Lottie Adams

Numerade Educator

Problem 119

Given the following information:
Heat of sublimation of $\mathrm{Li}(s)=166 \mathrm{kJ} / \mathrm{mol}$
Bond energy of $\mathrm{HCl}=427 \mathrm{kJ} / \mathrm{mol}$
Ionization energy of $\operatorname{Li}(g)=520 . \mathrm{k} \mathrm{J} / \mathrm{mol}$
Electron affinity of $\mathrm{Cl}(g)=-349 \mathrm{kJ} / \mathrm{mol}$
Lattice energy of $\mathrm{LiCl}(s)=-829 \mathrm{kJ} / \mathrm{mol}$
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 120

Use data in this chapter and Chapter 12 to discuss why $\mathrm{MgO}$ is an ionic compound but $\mathrm{CO}$ is not an ionic compound.

Lottie Adams

Numerade Educator

Problem 121

A promising new material with great potential as a fuel in solid rocket motors is ammonium dinitramide $\left[\mathrm{NH}_{4} \mathrm{N}\left(\mathrm{NO}_{2}\right)_{2}\right]$
a. Draw Lewis structures (including resonance forms) for the dinitramide ion $\left[\mathrm{N}\left(\mathrm{NO}_{2}\right)_{2}^{-}\right]$
b. Predict the bond angles around each nitrogen in the dinitramide ion.
c. Ammonium dinitramide can decompose explosively to nitrogen, water, and oxygen. Write a balanced equation for this reaction, and use bond energies to estimate $\Delta H$ for the explosive decomposition of this compound.
d. To estimate $\Delta H$ from bond energies, you made several assumptions. What are some of your assumptions?

Lottie Adams

Numerade Educator

Problem 122

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 $c,$ why do ionic bonds occur?
e. Given your explanations to part $\mathrm{d},$ why is $\mathrm{NaCl}$ stable but not $\mathrm{Na}_{2} \mathrm{Cl}_{2}$ and $\mathrm{NaCl}_{2} ?$ What about $\mathrm{MgO}$ compared to $\mathrm{MgO}_{2}$ and $\mathrm{Mg}_{2} \mathrm{O} ?$

Lottie Adams

Numerade Educator

Problem 123

The compound hexaazaisowurtzitane is one of the highest-energy explosives known (C $\mathscr{O}$ E News, p. 26 , Jan. 17,1994 ). The compound, also known as $\mathrm{CL}-20$ was first synthesized in $1987 .$ The method of synthesis and detailed performance data are still classified information because of CL-20's potential military application in rocket boosters and in warheads of "smart" weapons. The structure of $\mathrm{CL}-20$ 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. Three possible reactions for the explosive decomposition of CL-20 are
(EQUATION CANNOT COPY)
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?
(FIGURE CANNOT COPY)

Lottie Adams

Numerade Educator

Problem 124

In molecules of the type $\mathrm{X}-\mathrm{O}-\mathrm{H},$ as the electronegativity of $\mathrm{X}$ increases, the acid strength increases. In addition, if the electronegativity of $\mathrm{X}$ is a very small value, the molecule acts like a base. Explain these observations and provide examples.

Sima Sarker

Numerade Educator

Problem 125

Calculate the standard heat of formation of the compound ICl $(g)$ at $25^{\circ} \mathrm{C} .$ (Hint: Use Table 13.6 and Appendix $4 \text { data. })$

Lottie Adams

Numerade Educator

Problem 126

An ionic compound made from the metal $\mathrm{M}$ and the diatomic gas $\mathrm{X}_{2}$ has the formula $\mathrm{M}_{a} \mathrm{X}_{b},$ in which $a=1$ or
2 and $b=1$ or $2 .$ Use the data provided to determine the most likely values for $a$ and $b,$ along with the most likely charges for each of the ions in the ionic compound.
Data (in units of $\mathrm{k} \mathrm{J} / \mathrm{mol}$ ) Successive ionization energies of $\mathrm{M}: 480 ., 4750$ Successive electron affinity values for $\mathrm{X}:-175,920$ Enthalpy of sublimation for $\mathbf{M}(s) \rightarrow \mathbf{M}(g): 110$ Bond energy of $\mathrm{X}_{2}: 250$ Lattice energy for $\mathrm{MX}\left(\mathrm{M}^{+} \text {and } \mathrm{X}^{-}\right):-1200 . \mathrm{kJ} / \mathrm{mol}$
Lattice energy for $\mathrm{MX}_{2}\left(\mathrm{M}^{2+} \text { and } \mathrm{X}^{-}\right):-3500 . \mathrm{kJ} / \mathrm{mol}$
Lattice energy for $\mathrm{M}_{2} \mathrm{X}\left(\mathrm{M}^{+} \text {and } \mathrm{X}^{2-}\right):-3600 . \mathrm{kJ} / \mathrm{mol}$
Lattice energy for $\mathrm{MX}\left(\mathrm{M}^{2+} \text { and } \mathrm{X}^{2-}\right):-4800 . \mathrm{kJ} / \mathrm{mol}$

Ronald Prasad

Numerade Educator

Problem 127

Identify the following five compounds of $\mathrm{H}, \mathrm{N},$ and $\mathrm{O}$ For each compound, write a Lewis structure that is consistent with the information given.
a. All the compounds are electrolytes, although not all 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 A and C; nitrogen occurs in its lowest possible oxidation state in compounds $\mathrm{C}, \mathrm{D}$ and E. The formal charge on both nitrogens in compound $\mathrm{C}$ is $+1 ;$ the formal charge on the only nitrogen in compound B is $0 .$
c. Compounds $A$ and $E$ exist in solution. Both solutions give off gases. Commercially available concentrated solutions of compound A are normally 16 M. The commercial, concentrated solution of compound $\mathrm{E}$ is
$15 \mathrm{M}$
d. Commercial solutions of compound 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 D is $43.7 \%$ N and $50.0 \%$ 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 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 $A$ is acting as a strong electrolyte.
g. Solutions of compound C are weakly acidic; solutions of compound A are strongly acidic; solutions of compounds $\mathrm{B}$ and $\mathrm{E}$ are basic. The titration of $0.726 \mathrm{g}$ of compound $\mathrm{B}$ requires $21.98 \mathrm{mL}$ of $1.000 \mathrm{M} \mathrm{HCl}$ for complete neutralization.

Susan Hallstrom

Susan Hallstrom

Numerade Educator