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Chemistry 2012

JOHN E. MCMURRY, ROBERT C. FAY, JORDAN FANTINI

Chapter 19

The Main-Group Elements

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Problem 1

Predict which element in each of the following pairs has more non-metallic character:
(a) $\mathrm{B}$ or $\mathrm{Al}$
(b) Ge or Br $\quad$
(c) In or Se $\quad$
(d) Clor Te

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Problem 2

(a) Draw electron-dot structures for HNO_ and $\mathrm{H}_{3} \mathrm{PO}_{4},$ and suggest a reason for the difference in the formulas of these acids.
(b) Sulfur forms $\mathrm{SF}_{6},$ but oxygen bonds to a maximum of two $\mathrm{F}$ atoms, yielding $\mathrm{OF}_{2}$ . Explain.

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Problem 3

The organic solvent acetone has the molecular formula $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO}$ . The silicon analogue, a thermally stable lubricant, is a polymer, $\left[\left(\mathrm{CH}_{3}\right)_{2} \mathrm{SiOl}_{n}\right)$ Account for the difference in structure:

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Problem 4

Why doesn’t diborane have an ethane-like structure?

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Problem 5

Hydrogen cyanide, HCN, is a linear triatomic molecule. Draw its electron-dot structure, and indicate which hybrid orbitals are used by the carbon atom.

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Problem 6

The equilibrium between oxyhemoglobin and carboxyhemoglobin suggests an approach to treating mild cases of carbon monoxide poisoning. Explain.

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Problem 7

The following pictures represent silicate anions. What are the formula and charge of the anion in (a) and the repeating unit of the chain anion in (b)?

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Problem 8

For the molecules in Table 19.6 (page 779) that must be described as resonance hybrids, draw electron-dot resonance structures, assign formal charges, and indicate which resonance structure(s) is (are) most important. In addition, indicate which of the molecules in Table 19.6 are paramagnetic.

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Problem 9

Describe the relationship between the geometrical structures of white phophorus, tetraphosphorus hexoxide, and tetraphosphorus decoxide.

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Problem 10

Consider the following sulfur-containing oxoanions:
(a) Write the formula of each oxoanion, including its charge.
(b) Which oxoanion is the strongest acid?
(c) Which is the strongest base?
(d) Which is the weakest base?

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Problem 11

Write electron-dot structures for each of the following molecules, and use VSEPR theory to predict the structure of each:
$\begin{array}{ll}{\text { (a) } \mathrm{H}_{2} \mathrm{S}} & {\text { (b) } \mathrm{SO}_{2}} & {\text { (c) } \mathrm{SO}_{3}}\end{array}$

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Problem 12

What would be the effect of coating the laser printer drum with copper instead of selenium? Explain.

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Problem 13

Locate each of the following groups of elements on the periodic table:
$\begin{array}{ll}{\text { (a) Main-group elements }} & {\text { (b) s-Block elements }} \\ {\text { (c) } p-\text { -Block elements }} & {\text { (d) Main-group metals }} \\ {\text { (e) Nonmetals }} & {\text { (f) Semimetals }}\end{array}$

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Problem 14

Locate each of the following elements on the periodic table:
(a) Element with the lowest ionization energy
(b) Most electronegative element
(c) Group 4A element with the largest atomic radius
(d) Group 6A element with the smallest atomic radius
(e) Group 3A element that is a semiconductor
(f) Group 5 A element that forms the strongest $\pi$ bonds

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Problem 15

Locate the following elements on the periodic table:
(a) Elements that are gases at room temperature $\left(25^{\circ} \mathrm{C}\right)$
(b) A main-group element that is a liquid at $25^{\circ} \mathrm{C}$
(c) Nonmetals that are solids at $25^{\circ} \mathrm{C}$
(d) Elements that exist as diatomic molecules at $25^{\circ} \mathrm{C}$

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Problem 16

Locate the following elements on the periodic table, and write the formula of a compound that justifies each of your answers:
(a) Two nonmetals that can form more than four bonds
(b) Two nonmetals that form a maximum of four bonds
(c) Two nonmetals that form oxides that are gases at $25^{\circ} \mathrm{C}$
(d) A nonmetal that forms an oxide that is a solid at $25^{\circ} \mathrm{C}$

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Problem 17

Consider the six second- and third-row elements in groups $5 \mathrm{A}-7 \mathrm{A}$ of the periodic table:
Possible molecular structures for common allotropes of these elements are shown below:
(a) What is the molecular structure of each of the six elements?
(b) Using electron-dot structures, explain why each element has its particular molecular structure.
(c) Explain why nitrogen and phosphorus have different molecular structures and why oxygen and sulfur have different molecular structures, but fluorine and chlorine have the same molecular structure.

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Problem 18

Consider the six second- and third-row elements in groups 4A–6A of the periodic table:
Possible structures for the binary fluorides of each of these elements in its highest oxidation state are shown below.
(a) Identify the nonfluorine atom in each case, and write the molecular formula of each fluoride.
(b) Explain why the fluorides of nitrogen and phosphorus have different molecular structures, but the fluorides of carbon and silicon have the same molecular structure.

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Problem 19

The following models represent the structures of binary oxides of second- and third-row elements in their highest oxidation states:
(a) Identify the non-oxygen atom in each case, and write the molecular formula for each oxide.
(b) Draw an electron-dot structure for each oxide. For which oxides are resonance structures needed?

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Problem 20

The following models represent the structures of binary hydrides of second-row elements:
(a) Identify the nonhydrogen atom in each case, and write the molecular formula for each hydride.
(b) Draw an electron-dot structure for each hydride. For which hydride is there a problem in drawing the structure? Explain.

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Problem 21

The following pictures represent various silicate anions. Write the formula and charge of each anion.

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Problem 22

Which element in each of the following pairs has the higher ionization energy?
(a) S or Cl
(b) Si or Ge
(c) In or O

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Problem 23

Arrange the following elements in order of increasing ionization energy:

(a) P
(b) K
(c) Al
(d) F

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Problem 24

Which element in each of the following pairs has the larger atomic radius?
(a) B or Al
(b) P or S
(c) Pb or Br

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Problem 25

Arrange the following elements in order of increasing atomic radius:
(a) As
(b) O
(c) Sn
(d) S

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Problem 26

Which element in each of the following pairs has the higher electronegativity?
(a) Te or I
(b) N or P
(c) In or F

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Problem 27

Arrange the following elements in order of increasing electronegativity:
$\begin{array}{llll}{\text { (a) } \mathrm{N}} & {\text { (b) Ge }} & {\text { (c) } \mathrm{O}} & {\text { (d) } \mathrm{P}}\end{array}$

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Problem 28

Which element in each of the following pairs has more metallic character?
(a) Si or Sn
(b) Ge or Se
(c) Bi or I

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Problem 29

Which element in each of the following pairs has more nonmetallic character?

(a) S or Te
(b) Cl or P
(c) Bi or Br

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Problem 30

Which compound in each of the following pairs is more ionic?
(a) $\mathrm{CaH}_{2}$ or $\mathrm{NH}_{3}$
(b) $P_{4} \mathrm{O}_{6}$ or Ga_ $\mathrm{O}_{3}$
(c) SiCl_ or KCl $\quad$
(d) $\mathrm{BCl}_{3}$ or AlCl_

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Problem 31

Which compound in each of the following pairs is more covalent?
$\begin{array}{ll}{\text { (a) } \mathrm{PCl}_{3} \text { or AlF_ }_{3}} & {\text { (b) CaO or NO }} \\ {\text { (c) } \mathrm{NH}_{3} \text { or } \mathrm{KH}} & {\text { (d) } \mathrm{SnO}_{2} \text { or } \mathrm{SiO}_{2}}\end{array}$

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Problem 32

Which of the following compounds are molecular, and which have an extended three-dimensional structure?
$\begin{array}{llll}{\text { (a) } \mathrm{B}_{2} \mathrm{H}_{6}} & {\text { (b) } \mathrm{KAlSi}_{3} \mathrm{O}_{8}} & {\text { (c) } \mathrm{SO}_{3}} & {\text { (d) } \mathrm{GeCl}_{4}}\end{array}$

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Problem 33

Which of the following compounds are molecular, and which have an extended three-dimensional structure?
$\begin{array}{llll}{\text { (a) } \mathrm{KF}} & {\text { (b) } \mathrm{P}_{4} \mathrm{O}_{10}} & {\text { (c) } \mathrm{SiCl}_{4}} & {\text { (d) CaMgSi_{2} \mathrm { O } _ { 6 } }}\end{array}$

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Problem 34

Which oxide in each of the following pairs is more acidic?
$\begin{array}{ll}{\text { (a) } \mathrm{Al}_{2} \mathrm{O}_{3} \text { or } \mathrm{P}_{4} \mathrm{O}_{10}} & {\text { (b) } \mathrm{B}_{2} \mathrm{O}_{3} \text { or } \mathrm{Ga}_{2} \mathrm{O}_{3}} \\ {\text { (c) } \mathrm{SO}_{2} \text { or } \mathrm{SnO}_{2}} & {\text { (d) } \mathrm{As}_{2} \mathrm{O}_{3} \text { or } \mathrm{N}_{2} \mathrm{O}_{3}}\end{array}$

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Problem 35

Which oxide in each of the following pairs is more basic?
$\begin{array}{ll}{\text { (a) } \mathrm{SO}_{2} \text { or } \mathrm{SnO}_{2}} & {\text { (b) } \mathrm{In}_{2} \mathrm{O}_{3} \text { or } \mathrm{Ga}_{2} \mathrm{O}_{3}} \\ {\text { (c) } \mathrm{Al}_{2} \mathrm{O}_{3} \text { or } \mathrm{N}_{2} \mathrm{O}_{5}} & {\text { (d) BaO or MgO }}\end{array}$

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Problem 36

Consider the elements $\mathrm{C}, \mathrm{Se}, \mathrm{B}, \mathrm{Sn},$ Cl. Identify the element
on this list that:
(a) Has the largest atomic radius
(b) Is the most electronegative
(c) Is the best electrical conductor
(d) Has a maximum oxidation state of $+6$
(e) Forms a hydride with the empirical formula $X \mathrm{H}_{3}$

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Problem 37

Consider the elements $N,$ Si, Al, S, F. Identify which of these elements:
(a) Has the highest ionization energy
(b) Has the most metallic character
(c) Forms the strongest $\pi$ bonds
(d) Is a semiconductor
(e) Forms a 2 - anion

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Problem 38

$\mathrm{BF}_{3}$ reacts with $\mathrm{F}^{-}$ to give $\mathrm{BF}_{4}^{-},$ but AlF_ reacts with $\mathrm{F}^{-}$ to give $\mathrm{AlF}_{6}^{3-} .$ Explain.

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Problem 39

GeCl_ reacts with $\mathrm{Cl}^{-}$ to give $\mathrm{GeCl}_{6}^{2-},$ but $\mathrm{CCl}_{4}$ does not
react with excess $\mathrm{Cl}^{-}$ . Explain.

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Problem 40

At ordinary temperatures, sulfur exists as $\mathrm{S}_{8}$ but oxygen exists as $\mathrm{O}_{2}$ . Explain.

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Problem 41

Elemental nitrogen exists as $\mathrm{N}_{2},$ but white phosphorus exists as $\mathrm{P}_{4}$ . Explain.

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Problem 42

What is the most common oxidation state for each of the group 3 A elements?

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Problem 43

What is the oxidation state of the group 3 A element in each of the following compounds?
$\begin{array}{llll}{\text { (a) } \mathrm{NaBF}_{4}} & {\text { (b) GaCl_ }} & {\text { (c) TICl }} & {\text { (d) } \mathrm{B}_{2} \mathrm{H}_{6}}\end{array}$

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Problem 44

List three ways in which the properties of boron differ from those of the other group 3A elements.

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Problem 45

Explain why the properties of boron differ so markedly from the properties of the other group 3A elements.

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Problem 46

How is crystalline boron prepared? Write a balanced equation for the reaction.

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Problem 47

Write a balanced equation for the reduction of boron oxide by magnesium.

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Problem 48

Tell what is meant by:
(a) An electron-deficient molecule
(b) A three-center, two-electron bond Illustrate each definition with an example.

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Problem 49

Describe the structure of diborane $\left(\mathrm{B}_{2} \mathrm{H}_{6}\right),$ and explain why
the bridging $\mathrm{B}-\mathrm{H}$ bonds are longer than the terminal $\mathrm{B}-\mathrm{H}$ bonds.

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Problem 50

Identify the group 3 A element that best fits each of the following descriptions:
(a) Is the most abundant element of the group
(b) Is stable in the $+1$ oxidation state
(c) Is a semiconductor
(d) Forms a molecular fluoride

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Problem 51

Identify the group 3A element that best fits each of the following descriptions:

(a) Has an unusually low melting point
(b) Is the most electronegative
(c) Is extremely toxic
(d) Forms an acidic oxide

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Problem 52

Identify the group 4A element that best fits each of the following descriptions:
(a) Prefers the $+2$ oxidation state
(b) Forms the strongest $\pi$ bonds
(c) Is the second most abundant element in the Earth's crust
(d) Forms the most acidic oxide

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Problem 53

Select the group 4 A element that best fits each of the following descriptions:
(a) Forms the most basic oxide
(b) Is the least dense semimetal
(c) Is the second most abundant element in the human body
(d) Is the most electronegative

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Problem 54

Describe the geometry of each of the following molecules or ions, and tell which hybrid orbitals are used by the central atom:
$\begin{array}{llll}{\text { (a) } \operatorname{GeBr}_{4}} & {\text { (b) } \mathrm{CO}_{2}} & {\text { (c) } \mathrm{CO}_{3}^{2-}} & {\text { (d) } \mathrm{SnCl}_{3}-}\end{array}$

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Problem 55

What is the geometry of each of the following molecules or ions, and which hybrid orbitals are used by the central atom?
$\begin{array}{llll}{\text { (a) } \mathrm{SiO}_{4^4-}} & {\text { (b) } \mathrm{CCl}_{4}} & {\text { (c) } \mathrm{SnCl}_{2}} & {\text { (d) HCN }}\end{array}$

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Problem 56

List three properties of diamond, and account for them in terms of structure and bonding.

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Problem 57

Describe the structure and bonding in graphite, and explain why graphite is a good lubricant and a good electrical conductor.

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Problem 58

What is graphene, and how does it differ from graphite?

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Problem 59

Fullerene is soluble in nonpolar solvents, but graphite isn’t. Explain.

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Problem 60

Give the name and formula of a compound in which carbon exhibits an oxidation state of:
$\begin{array}{llll}{\text { (a) }+4} & {\text { (b) }+2} & {\text { (c) }-4}\end{array}$

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Problem 61

Give an example of an ionic carbide. What is the oxidation state of carbon in this substance?

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Problem 62

List three commercial uses for carbon dioxide, and relate each use to one of carbon dioxide’s properties.

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Problem 63

Why are $\mathrm{CO}$ and $\mathrm{CN}^{-}$ so toxic to humans?

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Problem 64

Describe the preparation of silicon from silica sand, and tell how silicon is purified for use in semiconductor devices. Write balanced equations for all reactions.

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Problem 65

How do the structures and properties of elemental silicon and germanium differ from those of tin and lead?

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Problem 66

Using the shorthand notation of Figure 19.5 (page 775$)$ draw the structure of the silicate anion in:
(a) $\mathrm{K}_{4} \mathrm{SiO}_{4} \quad$
(b) Ag$_{10} \mathrm{Si}_{4} \mathrm{O}_{13}$
What is the relationship between the charge on the anion and the number of terminal O atoms?

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Problem 67

Using the shorthand notation of Figure 19.5 (page 775$)$ draw the structure of the cyclic silicate anion in which four $\mathrm{SiO}_{4}$ tetrahedra share $\mathrm{O}$ atoms to form an eight-membered
ring of alternating Si and O atoms. Give the formula and charge of the anion.

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Problem 68

The silicate anion in the mineral kinoite is a chain of three SiO_ tetrahedra that share corners with adjacent tetrahedra. The mineral also contains $\mathrm{Ca}^{2+}$ ions, $\mathrm{Cu}^{2+}$ ions, and water molecules in a $1 : 1 : 1$ ratio.
(a) Give the formula and charge of the silicate anion.
(b) Give the complete formula for the mineral.

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Problem 69

Suggest a plausible structure for the silicate anion in each of the following minerals:
(a) Spodumene, $\mathrm{LiAlSi}_{2} \mathrm{O}_{6}$
(b) Wollastonite, $\mathrm{Ca}_{3} \mathrm{Si}_{3} \mathrm{O}_{9}$
(c) Thortveitite, $\mathrm{Sc}_{2} \mathrm{Si}_{2} \mathrm{O}_{7}$
(d) Albite, $\mathrm{NaAlSi}_{3} \mathrm{O}_{8}$

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Problem 70

Identify the group 5 A element(s) that best fits each of the following descriptions:
(a) Makes up part of bones and teeth
(b) Forms stable salts containing $\mathrm{M}^{3+}$ ions
(c) Is the most abundant element in the atmosphere
(d) Forms a basic oxide

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Problem 71

Identify the group 5 A element that best fits each of the following descriptions:
(a) Forms strong $\pi$ bonds $\quad$ (b) Is a metal
(c) Is the most abundant group 5A element in the Earth's crust
(d) Forms oxides with the group 5 A element in the $+1,+2,$ and $+4$ oxidation states

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Problem 72

Give the chemical formula for each of the following compounds, and indicate the oxidation state of the group 5 $\mathrm{A}$ element:
$\begin{array}{ll}{\text { (a) Nitrous oxide }} & {\text { (b) Hydrazine }} \\ {\text { (c) Calcium phosphide }} & {\text { (d) Phosphorous acid }} \\ {\text { (e) Arsenic acid }}\end{array}$

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Problem 73

Give the chemical formula for each of the following compounds, and indicate the oxidation state of the group 5 $\mathrm{A}$ element:
$\begin{array}{ll}{\text { (a) Nitric oxide }} & {\text { (b) Nitrous acid }} \\ {\text { (c) Phosphine }} & {\text { (d) Nitraphosphorus decoxide }} \\ {\text { (e) Phosphoric acid }}\end{array}$

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Problem 74

Draw an electron-dot structure for $\mathrm{N}_{2},$ and explain why this molecule is so unreactive.

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Problem 75

Draw electron-dot structures for:
(a) Nitrous oxide
(b) Nitric oxide
(c) Nitrogen dioxide
Predict the molecular geometry of each, and indicate which are expected to be paramagnetic.

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Problem 76

Predict the geometry of each of the following molecules or ions:
$\begin{array}{llll}{\text { (a) } \mathrm{NO}_{2}^{-}} & {\text { (b) } \mathrm{PH}_{3}} & {\text { (c) } \mathrm{PF}_{5}} & {\text { (d) } \mathrm{PCl}_{4}^{+}}\end{array}$

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Problem 77

Predict the geometry of each of the following molecules or ions:
$\begin{array}{llll}{\text { (a) } \mathrm{PCl}_{6}^{-}} & {\text { (b) } \mathrm{N}_{2} \mathrm{O}} & {\text { (c) } \mathrm{H}_{3} \mathrm{PO}_{3}} & {\text { (d) } \mathrm{NO}_{3}-}\end{array}$

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Problem 78

Describe the structures of the white and red allotropes of phosphorus, and explain why white phosphorus is so reactive.

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Problem 79

Draw the structure of each of the following molecules:
(a) Tetraphosphorus hexoxide
(b) Tetraphosphorus decoxide
(c) Phosphorous acid
(d) Phosphoric acid

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Problem 80

Account for each of the following observations:
(a) Phosphorous acid is a diprotic acid.
(b) Nitrogen doesn't exist as a four-atom molecule like $P_{4}$

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Problem 81

Account for each of the following observations:
(a) Nitric acid is a strong oxidizing agent, but phosphoric acid is not.
(b) Phosphorus, arsenic, and antimony form trichlorides and pentachlorides, but nitrogen forms only $\mathrm{NCl}_{3}$

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Problem 82

Write a balanced equation to account for each of the following observations:
(a) Nitric oxide turns brown when exposed to air.
(b) Nitric acid turns yellow-brown on standing.
(c) Silver dissolves in dilute $\mathrm{HNO}_{3},$ yielding a colorless gas.
(d) Hydrazine reduces iodine to $\mathrm{I}^{-}$ and in the process is oxidized to $\mathrm{N}_{2}$ gas.

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Problem 83

Describe the process used for the industrial production of the following chemicals:
$\begin{array}{ll}{\text { (a) Nitrogen }} {\text { (b) Ammonia }} \\ {\text { (c) Nitric acid }} {\text { (d) Phosphoric acid }}\end{array}$
Write balanced equations for all chemical reactions.

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Problem 84

Identify the group 6A element that best fits each of the following descriptions:
(a) Is the most electronegative
(b) Is a semimetal
(c) Is radioactive
(d) Is the most abundant element in the Earth's crust

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Problem 85

Identify the group 6 A element that best fits each of the following descriptions:
(a) Is a metal
(b) Is the most abundant element in the human body
(c) Is the strongest oxidizing agent
(d) Has the most negative electron affinity

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Problem 86

Describe the structure of the sulfur molecules in:
(a) Rhombic sulfur
(b) Monoclinic sulfur
(c) Plastic sulfur
(d) Liquid sulfur above $160^{\circ} \mathrm{C}$

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Problem 87

The viscosity of liquid sulfur increases sharply at about $160^{\circ} \mathrm{C}$ and then decreases again above $200^{\circ} \mathrm{C}$ . Explain.

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Problem 88

Give the name and formula of two compounds in which sulfur exhibits an oxidation state of:
$\begin{array}{llll}{\text { (a) }-2} & {\text { (b) }+4} & {\text { (c) }+6}\end{array}$

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Problem 89

What is the oxidation state of sulfur in each of the following compounds?
$\begin{array}{ll}{\text { (a) } \mathrm{HgS}} & {\text { (b) } \mathrm{Ca}\left(\mathrm{HSO}_{4}\right)_{2}} & {\text { (c) } \mathrm{H}_{2} \mathrm{SO}_{3}} \\ {\text { (d) } \mathrm{FeS}_{2}} & {\text { (e) } \mathrm{SF}_{4}}\end{array}$

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Problem 90

Describe the contact process for the manufacture of sulfuric acid, and write balanced equations for all reactions.

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Problem 91

Describe a convenient laboratory method for preparing each of the following compounds, and write balanced equations for all reactions:
(a) Sulfur dioxide (b) Hydrogen sulfide
(c) Sodium hydrogen sulfate

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Problem 92

Write a balanced net ionic equation for each of the following reactions:
(a) $\mathrm{Zn}(s)+$ dilute $\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow$
(b) $\mathrm{BaSO}_{3}(s)+\mathrm{HCl}(a q) \longrightarrow$
(c) $\mathrm{Cu}(s)+$ hot, conc $\mathrm{H}_{2} \mathrm{SO}_{4}(l) \longrightarrow$
(d) $\mathrm{H}_{2} \mathrm{S}(a q)+\mathrm{I}_{2}(a q) \longrightarrow$

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Problem 93

Write a balanced net ionic equation for each of the following reactions:
(a) $\mathrm{ZnS}(s)+\mathrm{HCl}(a q) \longrightarrow$
(b) $\mathrm{H}_{2} \mathrm{S}(a q)+\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}(a q) \longrightarrow$
(c) $\mathrm{Fe}(s)+$ dilute $\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow$
(d) $\mathrm{BaO}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow$

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Problem 94

Account for each of the following observations:
(a) $\mathrm{H}_{2} \mathrm{SO}_{4}$ is a stronger acid than $\mathrm{H}_{2} \mathrm{SO}_{3}$
(b) $\mathrm{SF}_{4}$ exists, but $\mathrm{OF}_{4}$ does not.
(c) The $\mathrm{S}_{8}$ ring is nonplanar.

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Problem 95

Account for each of the following observations:
(a) Oxygen is more electronegative than sulfur.
(b) Sulfur forms long $\mathrm{S}_{n}$ chains, but oxygen does not.
(c) The $\mathrm{SO}_{3}$ molecule is trigonal planar, but the $\mathrm{SO}_{3}^{2-}$ ion is trigonal pyramidal.

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Problem 96

Write the formula for each of the following compounds, and indicate the oxidation state of the halogen:
$\begin{array}{ll}{\text { (a) Bromic acid }} & {\text { (b) Hypoiodous acid }} \\ {\text { (c) Sodium chlorite }} & {\text { (d) Potassium metaperiodate }}\end{array}$

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Problem 97

$\begin{array}{l}{\text { Write the formula for each of the following compounds, }} \\ {\text { and indicate the oxidation state of the halogen: }} \\ {\text { (a) Potassium hypobromite } \quad \text { (b) Paraperiodic acid }} \\ {\text { (c) Sodium bromate }} & {\text { (d) Chlorous acid }}\end{array}$

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Problem 98

Name each of the following compounds:
$\begin{array}{llll}{\text { (a) HIO }_{3}} & {\text { (b) } \mathrm{HClO}_{2}} & {\text { (c) NaOBr }} & {\text { (d) LiClO_ }}\end{array}$

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Problem 99

Name each of the following compounds:
(a) $\mathrm{KClO}_{2} \quad$
(b) HIO_ $_{4}$
(c) HOBr
(d) NaBrO_ $_{3}$

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Problem 100

Write an electron-dot structure for each of the following
molecules or ions, and predict the molecular geometry:
$\begin{array}{llll}{\text { (a) } \mathrm{HIO}_{3}} & {\text { (b) } \mathrm{ClO}_{2}^{-}} & {\text { (c) HOCl }} & {\text { (d) } \mathrm{IO}_{6^5-}}\end{array}$

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Problem 101

Write an electron-dot structure for each of the following molecules or ions, and predict the molecular geometry:
$\begin{array}{llll}{\text { (a) } \mathrm{BrO}_{4}^{-}} & {\text { (b) } \mathrm{ClO}_{3}} & {\text { (c) HIO_ }} & {\text { (d) HOBr }}\end{array}$

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Problem 102

Explain why acid strength increases in the order
$\mathrm{HClO} <\mathrm{HClO}_{2} <\mathrm{HClO}_{3}< \mathrm{HClO}_{4}$

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Problem 103

Explain why acid strength increases in the order
$\mathrm{HIO}< \mathrm{HBrO} <\mathrm{HClO}$ .

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Problem 104

Write a balanced net ionic equation for each of the following reactions:
(a) $\operatorname{Br}_{2}(l)+\operatorname{cold} \mathrm{NaOH}(a q) \longrightarrow$
(b) $\mathrm{Cl}_{2}(g)+\operatorname{cold} \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow$
(c) $\mathrm{Cl}_{2}(g)+\operatorname{hot} \mathrm{NaOH}(a q) \longrightarrow$

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Problem 105

Write a balanced equation for the reaction of potassium chlorate and sucrose. The products are $\mathrm{KCl}(s), \mathrm{CO}_{2}(g),$ and $\mathrm{H}_{2} \mathrm{O}(g) .$

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Problem 106

Write a balanced net ionic equation for the reaction between magnesium and hot, concentrated sulfuric acid, a reaction similar to that between hot, concentrated sulfuric acid and copper.

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Problem 107

Choose the compound in Table 19.6 that is used as a rocket fuel. What nitrogen-containing compound is used as the oxidizer?

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Problem 108

Does the silicate hedenbergite, CaFeSi_ $\mathrm{O}_{6},$ contain single-stranded or double-stranded silicate chains? (Draw comparisons with Figures 19.6 and 19.7 )

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Problem 109

An iron object exposed to rain is eventually damaged by rusting, but a similarly placed aluminum object is visibly unchanged. Explain.

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Problem 110

Hydrazine can be used to remove small amounts of dissolved oxygen from the water used in boilers. Write a balanced equation for the reaction if the products are nitrogen and water.

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Problem 111

Iodine forms the acid anhydride $\mathrm{I}_{2} \mathrm{O}_{5} .$ Write a balanced equation for the reaction of this anhydride with water, and name the acid that is formed.

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Problem 112

Which compound in each of the following pairs has the higher melting point?
$\begin{array}{llll}{\text { (a) LiCl or } \mathrm{PCl}_{3}} & {\text { (b) } \mathrm{CO}_{2} \text { or } \mathrm{SiO}_{2}} & {\text { (c) } \mathrm{P}_{4} \mathrm{O}_{10} \text { or } \mathrm{NO}_{2}}\end{array}$

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Problem 113

Which element in each of the following pairs is the better electrical conductor?
$\begin{array}{llll}{\text { (a) } \mathrm{B} \text { or Ga }} & {\text { (b) In or S }} & {\text { (c) Pb or } \mathrm{P}}\end{array}$

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Problem 114

Draw the structure of graphene.

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Problem 115

Compare and contrast the properties of ammonia and phosphine.

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Problem 116

How many of the four most abundant elements in the Earth's crust and in the human body can you identify without consulting Figure 19.1$?$

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Problem 117

Identify as many of the 10 most important industrial chemicals as you can without consulting Table 19.1

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Problem 118

Which of the group 4A elements have allotropes with the diamond structure? Which have metallic allotropes? How does the variation in the structure of the group 4 A elements illustrate how metallic character varies down a periodic group?

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Problem 119

Write a balanced chemical equation for a laboratory preparation of each of the following compounds:
$\begin{array}{ll}{\text { (a) } \mathrm{NH}_{3}} & {\text { (b) } \mathrm{CO}_{2}} & {\text { (c) } \mathrm{B}_{2} \mathrm{H}_{6} \text { (diborane) }} \\ {\text { (d) } \mathrm{C}_{2} \mathrm{H}_{2} \text { (acetylene) (e) } \mathrm{N}_{2} \mathrm{O}} & {\text { (f) } \mathrm{NO}_{2}}\end{array}$

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Problem 120

Write balanced equations for the reactions of (a) $\mathrm{H}_{3} \mathrm{PO}_{4}$ and
(b) $\mathrm{B}(\mathrm{OH})_{3}$ with water. Classify each acid as a Bronsted-Lowry acid or a Lewis acid.

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Problem 121

What oxoanion is used for these purposes?
(a) Oxidizing agent in space shuttle booster rockets
(b) Oxidizing agent in chlorine bleach
(c) Oxidizing agent in matches and fireworks

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Problem 122

Account for each of the following observations:
(a) Diamond is extremely hard and high melting, whereas graphite is very soft and high melting.
(b) Chlorine does not form a perhalic acid, $\mathrm{H}_{5} \mathrm{ClO}_{6}$

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Problem 123

So-called fuming sulfuric acid is formed when sulfur trioxide dissolves in anhydrous sulfuric acid to form $\mathrm{H}_{2} \mathrm{S}_{2} \mathrm{O}_{7}$ Propose a structure for $\mathrm{H}_{2} \mathrm{S}_{2} \mathrm{O}_{7},$ which contains an
$\mathrm{S}-\mathrm{O}-$ S linkage.

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Problem 124

Chlorine reacts with molten sulfur to yield disulfur dichloride, a yellowish-red liquid. Propose a structure for disulfur dichloride.

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Problem 125

The organ pipes in an unheated Estonian church are pitted and crumbling to powder in places. Suggest an explanation, given that the pipes are made from tin.

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Problem 126

Of ammonia, hydrazine, and hydroxylamine, which reacts to the greatest extent with the weak acid $\mathrm{HNO}_{2} ?$ Consult Appendix $\mathrm{C}$ for equilibrium constants.

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Problem 127

A fullerene that is 97.28$\% \mathrm{C}$ has an atom within the $\mathrm{C}_{60}$ cage. Is the compound He@C, or Ne@C_{60? }

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Problem 128

Suggest a structure for the mixed aluminum-boron hydride $AlBH_6$.

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Problem 129

Suggest a benefit and a limitation to using gallium as the material in a thermometer.

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Problem 130

A sample of $\mathrm{P}_{4}$ burned in excess oxygen and formed a phosphorus oxide. The phosphorus oxide was dissolved carefully in enough water to make 1.00 $\mathrm{L}$ of solution with
$\mathrm{pH}=1.93 .$ What is the identity of the phosphorus oxide and the oxoacid that was formed, and how much $P_{4}$ in grams, was burned? See Appendix C for acid dissociation constants

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Problem 131

Give one example from main-group chemistry that illustrates each of the following descriptions:

(a) Covalent network solid
(b) Disproportionation reaction
(c) Paramagnetic oxide
(d) Polar molecule that violates the octet rule
(e) Lewis acid
(f) Amphoteric oxide
(g) Semiconductor
(h) Strong oxidizing agent
(i) Allotropes

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Problem 132

Could the strain in the $\mathrm{P}_{4}$ molecule be reduced by using $s p^{3}$ hybrid orbitals in bonding instead of pure $p$ orbitals? Explain.

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Problem 133

Carbon is an essential element in the molecules on which life is based. Would silicon be equally satisfactory? Explain.

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Problem 134

An important physiological reaction of nitric oxide (NO) is
its interaction with the superoxide ion $\left(\mathrm{O}_{2}\right)$ to form the
peroxynitrite ion $(\mathrm{ONOO})$ .
(a) Write electron-dot structures for $\mathrm{NO}, \mathrm{O}_{2}^{-},$ and $\mathrm{ONOO}^{-},$ and predict the $\mathrm{O}-\mathrm{N}-\mathrm{O}$ bond angle in $\mathrm{ONOO}^{-}$
(b) The bond length in NO $(115 \text { pm) is intermediate }$etween the length of an NO triple bond and an NO double bond. Account for the bond length and the paramagnetism of NO using molecular orbital theory.

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Problem 135

Consider phosphorous acid, a polyprotic acid with formula $\mathrm{H}_{3} \mathrm{PO}_{3}$
(a) Draw two plausible structures for $\mathrm{H}_{3} \mathrm{PO}_{3} .$ For each one, predict the shape of the pH titration curve for the titration of the $\mathrm{H}_{3} \mathrm{PO}_{3}\left(K_{\mathrm{al}}=1.0 \times 10^{-2}\right)$ with aqueous $\mathrm{NaOH}$
(b) For the structure with the $\mathrm{H}$ atoms in two different environments, calculate the $\mathrm{pH}$ at the first and second equivalence points assuming that 30.00 $\mathrm{mL}$ of 0.1240 $\mathrm{M} \mathrm{H}_{3} \mathrm{PO}_{3}\left(K_{\mathrm{a} 2}=2.6 \times 10^{-7}\right)$ is titrated with 0.1000 $\mathrm{M} \mathrm{NaOH} .$

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Problem 136

We've said that the $+1$ oxidation state is uncommon for indium but is the most stable state for thallium. Verify this statement by calculating $E^{\circ}$ and $\Delta G^{\circ}$ (in kilojoules) for the disproportionation reaction $\quad 3 \mathrm{M}^{+}(a q) \longrightarrow \mathrm{M}^{3+}(a q)+2 \mathrm{M}(s) \quad \mathrm{M}=$ In or T1 Is disproportionation a spontaneous reaction for $\operatorname{In}^{+}$ and/ or $\mathrm{T}^{+}$ ? Standard reduction potentials for the relevant
half-reactions are
$\begin{array}{ll}{\operatorname{In}^{3+}(a q)+2 \mathrm{e}^{-} \longrightarrow \operatorname{In}^{+}(a q)} & {E^{\circ}=-0.44 \mathrm{V}} \\ {\operatorname{In}^{+}(a q)+\mathrm{e}^{-} \longrightarrow \operatorname{In}(s)} & {E^{\circ}=-0.14 \mathrm{V}}\end{array}$
$\begin{array}{ll}{\mathrm{T}^{3+}(a q)+2 \mathrm{e}^{-} \longrightarrow \mathrm{Tl}^{+}(a q)} & {E^{\circ}=+1.25 \mathrm{V}} \\ {\mathrm{T}^{+}(a q)+\mathrm{e}^{-} \longrightarrow \mathrm{Tl}(s)} & {E^{\circ}=-0.34 \mathrm{V}}\end{array}$

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Problem 137

Terrorists often use ammonium nitrate fertilizer as an ingredient in car bombs. When ammonium nitrate explodes, it decomposes to gaseous nitrogen, oxygen, and water vapor. The force of the explosion results from the sudden production of a huge volume of hot gas.
(a) Write a balanced equation for the reaction.
(b) What volume of gas (in liters) is produced from the explosion of 1.80 $\mathrm{m}^{3}$ of solid $\mathrm{NH}_{4} \mathrm{NO}_{3} ?$ Assume that the gas has a temperature of $500^{\circ} \mathrm{C}$ and a pressure of 1.00 $\mathrm{atm}$ . The density of $\mathrm{NH}_{4} \mathrm{NO}_{3}$ is 1.725 $\mathrm{g} / \mathrm{cm}^{3}$ .
(c) Use the thermodynamic data in Appendix $\mathrm{B}$ to calculate the amount of heat (in kilojoules) released in the reaction.

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Problem 138

It has been claimed that $\mathrm{NH}_{4} \mathrm{NO}_{3}$ fertilizer can be rendered
unexplodable (see Problem 19.137) by adding compounds such as diammonium hydrogen phosphate, (NH_) 2 $\mathrm{HPO}_{4}$ . Analysis of such a desensitized sample of $\mathrm{NH}_{4} \mathrm{NO}_{3}$ showed the mass $\%$ nitrogen to be 33.81$\% .$
(a) Assuming that the mixture contains only $\mathrm{NH}_{4} \mathrm{NO}_{3}$ and
$\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4}$ , what is the mass percent of each of these
two components?
(b) A 0.965 g sample of the mixture was dissolved in enough water to make 50.0 $\mathrm{mL}$ of solution. What is the $\mathrm{pH}$ of the solution? (Hint: The strongest base present is $\mathrm{HPO}_{4}^{2-} . )$

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Problem 139

A 5.00 g quantity of white phosphorus was burned in an excess of oxygen, and the product was dissolved in enough water to make 250.0 $\mathrm{mL}$ of solution.
(a) Write balanced equations for the reactions.
(b) What is the pH of the solution?
(c) When the solution was treated with an excess of aqueous $\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2},$ a white precipitate was obtained. Write a
balanced equation for the reaction, and calculate the mass of the precipitate in grams.
(d) The precipitate in part (c) was removed, and the solution that remained was treated with an excess of zinc, yielding a colorless gas that was collected at $20^{\circ} \mathrm{C}$ and 742 $\mathrm{mm}$ Hg. Identify the gas, and determine its volume.

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Problem 140

A 500.0 mL sample of an equilibrium mixture of gaseous $\mathrm{N}_{2} \mathrm{O}_{4}$ and $\mathrm{NO}_{2}$ at $25^{\circ} \mathrm{C}$ and 753 $\mathrm{mm}$ Hg pressure was allowed to react with enough water to make 250.0 $\mathrm{mL}$ of solution at $25^{\circ} \mathrm{C}$ . You may assume that all the dissolved $\mathrm{N}_{2} \mathrm{O}_{4}$ is converted to $\mathrm{NO}_{2},$ which disproportionates in water, yielding a solution of nitrous acid and nitric acid. Assume further that the disproportionation reaction goes to completion and that none of the nitrous acid disproportionates. The equilibrium constant $K_{\mathrm{p}}$ for the reaction $\mathrm{N}_{2} \mathrm{O}_{4}(g) \Longrightarrow 2 \mathrm{NO}_{2}(g)$ is 0.113 at $25^{\circ} \mathrm{C} . K_{\mathrm{a}}$ for $\mathrm{HNO}_{2}$ is 4.5 $\times 10^{-4}$ at $25^{\circ} \mathrm{C}$ .
(a) Write a balanced equation for the disproportionation reaction.
(b) What is the molar concentration of $\mathrm{NO}_{2}^{-},$ and what is the $\mathrm{pH}$ of the solution?
(c) What is the osmotic pressure of the solution in atmospheres?
(d) How many grams of lime (CaO) would be needed to neutralize the solution?

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