Chapter Questions
Although the earth was formed from the same interstellar material as the sun, there is little elemental hydrogen $\left(\mathrm{H}_{2}\right)$ in the earth's atmosphere. Explain.
Many lithium salts are hygroscopic (absorb water), whereas the corresponding salts of the other alkali metals are not. Explain.
How do the acidities of the aqueous solutions of the alkaline earth metal ions $\left(\mathrm{M}^{2+}\right)$ change in going down the group?
What are three-centered bonds?
Why is graphite a good lubricant? What advantages does it have over grease- or oil-based lubricants?
What are some of the structural differences between quartz and amorphous $\mathrm{SiO}_{2}$ ?
What type of semiconductor is formed when a Group 3 A element is added as an impurity to $\mathrm{Si}$ or $\mathrm{Ge}$ ?
Diagonal relationships in the periodic table exist as well as the vertical relationships. For example, Be and $\mathrm{Al}$ are similar in some of their properties as are $\mathrm{B}$ and Si. Rationalize why these diagonal relationships hold for properties such as size, ionization energy, and electron affinity.
Atomic size seems to play an important role in explaining some of the differences between the first element in a group and the subsequent group elements. Explain.
What will be the atomic number of the next alkali metal to be discovered? How would you expect the physical properties of the next alkali metal to compare with the properties of the other alkali metals summarized in Table $19.4$ ?
In most compounds, the solid phase is denser than the liquid phase. Why isn't this true for water?
Beryllium shows some covalent characteristics in some of its compounds, unlike the other alkaline earth halides. Give a possible explanation for this phenomenon.
Hydrogen is produced commercially by the reaction of methane with steam:$$\mathrm{CH}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightleftharpoons \mathrm{CO}(g)+3 \mathrm{H}_{2}(g)$$a. Calculate $\Delta H^{\circ}$ and $\Delta S^{\circ}$ for this reaction (use the data in Appendix 4 ).b. What temperatures will favor product formation at standard conditions? Assume $\Delta H^{\circ}$ and $\Delta S^{\circ}$ do not depend on temperature.
The major industrial use of hydrogen is in the production of ammonia by the Haber process:$$3 \mathrm{H}_{2}(g)+\mathrm{N}_{2}(g) \rightarrow 2 \mathrm{NH}_{3}(g)$$a. Using data from Appendix 4 , calculate $\Delta H^{\circ}, \Delta S^{\circ}$, and $\Delta G^{\circ}$ for the Haber process reaction.b. Is the reaction spontaneous at standard conditions?c. At what temperatures is the reaction spontaneous at standard conditions? Assume $\Delta H^{\circ}$ and $\Delta S^{\circ}$ do not depend on temperature.
Name each of the following compounds.a. $\mathrm{Li}_{2} \mathrm{O}$b. $\mathrm{KO}_{2}$c. $\mathrm{Na}_{2} \mathrm{O}_{2}$
Write the formula for each of the following compounds.a. lithium nitridec. rubidium hydroxideb. potassium carbonated. sodium hydride
Complete and balance the following reactions.a. $\mathrm{Li}_{2} \mathrm{O}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow$b. $\mathrm{Na}_{2} \mathrm{O}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow$c. $\mathrm{LiH}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow$d. $\mathrm{KO}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow$
Write balanced equations describing the reaction of lithium metal with each of the following: $\mathrm{O}_{2}, \mathrm{~S}_{8}, \mathrm{Cl}_{2}, \mathrm{P}_{4}, \mathrm{H}_{2}, \mathrm{H}_{2} \mathrm{O}$, and $\mathrm{HCl}$.
Lithium reacts with acetylene in liquid ammonia to produce $\mathrm{LiC}_{2} \mathrm{H}$ (lithium acetylide, $\mathrm{LiC}=\mathrm{CH}$ ) and hydrogen gas. Write a balanced equation for this reaction. What type of reaction is this?
The electrolysis of aqueous sodium chloride (brine) is an important industrial process for the production of chlorine and sodium hydroxide. In fact, this process is the second largest consumer of electricity in the United States, after the production of aluminum. Write a balanced equation for the electrolysis of aqueous sodium chloride (hydrogen gas is also produced).
Name each of the following compounds.a. $\mathrm{MgCO}_{3}$b. $\mathrm{BaSO}_{4}$c. $\mathrm{Sr}(\mathrm{OH})_{2}$
Write the formula for each of the following compounds.$\begin{array}{lll}\text { a. calcium nitride } & \text { b. beryllium chloride } & \text { c. barium hydride }\end{array}$
One harmful effect of acid rain is the deterioration of structures and statues made of marble or limestone, both of which are essentially calcium carbonate. The reaction of calcium carbonate with sulfuric acid yields carbon dioxide, water, and calcium sulfate. Because calcium sulfate is marginally soluble in water, part of the object is washed away by the rain. Write a balanced chemical equation for the reaction of sulfuric acid with calcium carbonate.
Write balanced equations describing the reaction of Sr with each of the following: $\mathrm{O}_{2}, \mathrm{~S}_{\mathrm{s}}, \mathrm{Cl}_{2}, \mathrm{P}_{4}, \mathrm{H}_{2}, \mathrm{H}_{2} \mathrm{O}$, and $\mathrm{HCl}$.
Predict the structure of $\mathrm{BeF}_{2}$ in the gas phase. What structure would you predict for $\mathrm{BeF}_{2}(s) ?$
The beryllium atom in $\mathrm{BeCl}_{2}$ is electron-deficient (only four valence electrons surround it), which makes it very reactive toward electron-pair donors such as ammonia. Draw a Lewis structure for the expected product when $\mathrm{BeCl}_{2}$ reacts with excess ammonia.
The U.S. Public Health Service recommends the fluoridation of water as a means for preventing tooth decay. The recommended concentration is $1 \mathrm{mg} \mathrm{F}^{-}$ per liter. The presence of calcium ions in hard water can precipitate the added fluoride. What is the maximum molarity of calcium ions in hard water if the fluoride concentration is at the USPHS recommended level? ( $K_{\text {sp }}$ for $\mathrm{CaF}_{2}=$ $\left.4.0 \times 10^{-11}\right)$
Slaked lime, $\mathrm{Ca}(\mathrm{OH})_{2}$, is used to soften hard water by removing calcium ions from hard water through the reaction$\mathrm{Ca}(\mathrm{OH})_{2}(a q)+\mathrm{Ca}^{2+}(a q)+2 \mathrm{HCO}_{3}^{-}(a q) \rightarrow$$2 \mathrm{CaCO}_{3}(s)+2 \mathrm{H}_{2} \mathrm{O}(l)$Although $\mathrm{CaCO}_{3}(s)$ is considered insoluble, some of it does dissolve in aqueous solutions. Calculate the molar solubility of $\mathrm{CaCO}_{3}$ in water $\left(K_{\mathrm{sp}}=8.7 \times 10^{-4}\right)$.
What mass of barium is produced when molten $\mathrm{BaCl}_{2}$ is electrolyzed by a current of $2.50 \times 10^{5} \mathrm{~A}$ for $6.00 \mathrm{~h}$ ?
Electrolysis of an alkaline earth metal chloride using a current of $5.00 \mathrm{~A}$ for 748 s deposits $0.471 \mathrm{~g}$ of metal at the cathode. What is the identity of the alkaline earth metal chloride?
Write the formula for each of the following compounds.a. aluminum nitrideb. gallium fluoridec. gallium sulfide
Thallium and indium form $+1$ and $+3$ oxidation states when in compounds. Predict the formulas of the possible compounds between thallium and oxygen and between indium and chlorine. Name the compounds.
Boron hydrides were once evaluated for possible use as rocket fuels. Complete and balance the following equation for the combustion of diborane.$$\mathrm{B}_{2} \mathrm{H}_{6}+\mathrm{O}_{2} \longrightarrow \mathrm{B}(\mathrm{OH})_{3}$$
Elemental boron is produced by reduction of boron oxide with magnesium to give boron and magnesium oxide. Write a balanced equation for this reaction.
$\mathrm{Ga}_{2} \mathrm{O}_{3}$, is an amphoteric oxide, and $\mathrm{In}_{2} \mathrm{O}_{3}$ is a basic oxide. Write equations for the reactions that illustrate these properties.
Aluminum hydroxide is amphoteric and will dissolve in both acidic and basic solutions. Write balanced chemical equations representing each process.
Write equations describing the reactions of Ga with each of the following: $\mathrm{F}_{2}, \mathrm{O}_{2}, \mathrm{~S}_{\mathrm{x}}, \mathrm{N}_{2}$, and $\mathrm{HCl}$.
Write a balanced equation describing the reaction of aluminum metal with concentrated aqueous sodium hydroxide.
Draw Lewis structures for $\mathrm{CF}_{4}, \mathrm{GeF}_{4}$, and $\mathrm{GeF}_{6}{ }^{2-}$. Predict the molecular structure (including bond angles), and give the expected hybridization of the central atom in these three substances. Explain why $\mathrm{CF}_{6}^{2-}$ does not form.
Carbon and sulfur form compounds with the formulas $\mathrm{CS}_{2}$ and $\mathrm{C}_{3} \mathrm{~S}_{2}$. Draw Lewis structures and predict the shapes of these two compounds.
Silicon is produced for the chemical and electronics industries by the following reactions. Give the balanced equation for each reaction.a. $\mathrm{SiO}_{2}(s)+\mathrm{C}(s) \rightarrow \mathrm{Si}(s)+\mathrm{CO}(g)$b. Silicon tetrachloride is reacted with very pure magnesium, producing silicon and magnesium chloride.c. $\mathrm{Na}_{2} \mathrm{SiF}_{6}(s)+\mathrm{Na}(s) \rightarrow \mathrm{Si}(s)+\mathrm{NaF}(s)$
Write equations describing the reactions of $\mathrm{Sn}$ with each of the following: $\mathrm{Cl}_{2}, \mathrm{O}_{2}$, and $\mathrm{HCl}$.
Why are people advised not to drink hot tap water if their plumbing contains lead solder?
Calculate the solubility of $\mathrm{Pb}(\mathrm{OH})_{2}\left(K_{\mathrm{sp}}=1.2 \times 10^{-15}\right)$ in water. Is $\mathrm{Pb}(\mathrm{OH})_{2}$ more or less soluble in acidic solutions? Explain.
The fermentation of glucose produces ethanol and carbon dioxide. Write a balanced equation for this reaction.
Tin forms compounds in the $+2$ and $+4$ oxidation states. Therefore, when tin reacts with fluorine, two products are possible. Write balanced equations for the production of the two tin halide compounds and name them.
The resistivity (a measure of electrical resistance) of graphite is $(0.4$ to $5.0) \times 10^{-4} \mathrm{ohm} \cdot \mathrm{cm}$ in the basal plane. (The basal plane is the plane of the six-membered rings of carbon atoms.) The resistivity is $0.2$ to $1.0 \mathrm{ohm} \cdot \mathrm{cm}$ along the axis perpendicular to the plane. The resistivity of diamond is $10^{14}$ to $10^{16} \mathrm{ohm} \cdot \mathrm{cm}$ and is independent of direction. How can you account for this behavior in terms of the structures of graphite and diamond?
Silicon carbide $(\mathrm{SiC})$ is an extremely hard substance. Propose a structure for $\mathrm{SiC}$.
A $0.250-\mathrm{g}$ chunk of sodium metal is cautiously dropped into a mixture of $50.0 \mathrm{~g}$ of water and $50.0 \mathrm{~g}$ of ice, both at $0{ }^{\circ} \mathrm{C}$. The reaction is$2 \mathrm{Na}(s)+2 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 2 \mathrm{NaOH}(a q)+\mathrm{H}_{2}(g) \quad \Delta H=-368 \mathrm{~kJ}$Will the ice melt? Assuming the final mixture has a specific heat capacity of $4.18 \mathrm{~J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}$, calculate the final temperature. The enthalpy of fusion for ice is $6.02 \mathrm{~kJ} / \mathrm{mol}$.
One of the chemical controversies of the nineteenth century concerned the element beryllium (Be). Berzelius originally claimed that beryllium was a trivalent element (forming $\mathrm{Be}^{3+}$ ions) and that it gave an oxide with the formula $\mathrm{Be}_{2} \mathrm{O}_{3} .$ This resulted in a calculated atomic mass of $13.5$ for beryllium. In formulating his periodic table, Mendeleev proposed that beryllium was divalent (forming $\mathrm{Be}^{2+}$ ions) and that it gave an oxide with the formula BeO. This assumption gives an atomic mass of $9.0 .$ In $1894, \mathrm{~A}$. Combes (Comptes Rendus 1894, p. 1221$)$ reacted beryllium with the anion $\mathrm{C}_{5} \mathrm{H}_{7} \mathrm{O}_{2}^{-}$ and measured the density of the gaseous product. Combes's data for two different experiments are as follows:If beryllium is a divalent metal, the molecular formula of the product will be $\mathrm{Be}\left(\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{O}_{2}\right)_{2} ;$ if it is trivalent, the formula will be $\mathrm{Be}\left(\mathrm{C}_{5} \mathrm{H}_{7} \mathrm{O}_{2}\right)_{3} .$ Show how Combes's data help to confirm that beryllium is a divalent metal.
It takes $15 \mathrm{kWh}$ (kilowatt-hours) of electrical energy to produce $1.0 \mathrm{~kg}$ of aluminum metal from aluminum oxide by the Hall-Heroult process. Compare this to the amount of energy necessary to melt $1.0 \mathrm{~kg}$ of aluminum metal. Why is it economically feasible to recycle aluminum cans? (The enthalpy of fusion for aluminum metal is $10.7 \mathrm{~kJ} / \mathrm{mol}[1$ watt $=1 \mathrm{~J} / \mathrm{s}] .)$
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.
Carbon monoxide is toxic because it bonds much more strongly to the iron in hemoglobin (Hgb) than does $\mathrm{O}_{2}$. Consider the following reactions and approximate standard free energy changes:$$\begin{aligned}\mathrm{Hgb}+\mathrm{O}_{2} \longrightarrow \mathrm{HgbO}_{2} & \Delta G^{\circ} &=-70 \mathrm{~kJ} \\\mathrm{Hgb}+\mathrm{CO} \longrightarrow \mathrm{HgbCO} & \Delta G^{a} &=-80 \mathrm{~kJ}\end{aligned}$$Using these data, estimate the equilibrium constant value at $25^{\circ} \mathrm{C}$ for the following reaction:$$\mathrm{HgbO}_{2}+\mathrm{CO} \rightleftharpoons \mathrm{HgbCO}+\mathrm{O}_{2}$$
The three most stable oxides of carbon are carbon monoxide (CO), carbon dioxide $\left(\mathrm{CO}_{2}\right)$, and carbon suboxide $\left(\mathrm{C}_{3} \mathrm{O}_{2}\right) .$ The space filling models for these three compounds are For each oxide, draw the Lewis structure, predict the molecular structure, and describe the bonding (in terms of the hybrid orbitals for the carbon atoms).
The overall reaction in the lead storage battery is $\mathrm{Pb}(s)+\mathrm{PbO}_{2}(s)+2 \mathrm{H}^{+}(a q)+2 \mathrm{HSO}_{4}^{-}(a q) \longrightarrow$$2 \mathrm{PbSO}_{4}(s)+2 \mathrm{H}_{2} \mathrm{O}(l)$Calculate 8 at $25^{\circ} \mathrm{C}$ for this battery when $\left[\mathrm{H}_{2} \mathrm{SO}_{4}\right]=4.5 M$, that is, $\left[\mathrm{H}^{+}\right]=\left[\mathrm{HSO}_{4}^{-}\right]=4.5 M .$ At $25^{\circ} \mathrm{C}, \mathscr{E}^{\circ}=2.04 \mathrm{~V}$ for the leadstorage battery.
The bright yellow light emitted by a sodium vapor lamp consists of two emission lines at $589.0$ and $589.6 \mathrm{~nm}$. What are the frequency and the energy of a photon of light at each of these wavelengths? What are the energies in $\mathrm{kJ} / \mathrm{mol}$ ?
In the 1950 s and 1960 s, several nations conducted tests of nuclear warheads in the atmosphere. It was customary following each test to monitor the concentration of strontium-90 (a radioactive isotope of strontium) in milk. Why would strontium-90 tend to accumulate in milk?
The compound $\mathrm{BeSO}_{4} \cdot 4 \mathrm{H}_{2} \mathrm{O}$ cannot be dehydrated easily by heating. It dissolves in water to give an acidic solution. Explain these observations.
The inert-pair effect is sometimes used to explain the tendency of heavier members of group $3 \mathrm{~A}$ to exhibit $+1$ and $+3$ oxidation states. What does the inert-pair effect reference? Hint: Consider the valence electron configuration for group $3 \mathrm{~A}$ elements.
Assume that element 113 is produced. What is the expected electron configuration for element 113 ?
Calculate the $\mathrm{pH}$ of a $0.050 \mathrm{M} \mathrm{Al}\left(\mathrm{NO}_{3}\right)_{3}$ solution. The $K_{\mathrm{a}}$ value for $\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}^{3+}$ is $1.4 \times 10^{-5}$.
The compound with the formula $\mathrm{T} \mathrm{II}_{3}$ is a black solid. Given the following standard reduction potentials:$$\begin{aligned}\mathrm{TI}^{3+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Tl}^{+} & \mathscr{g}^{\circ}=+1.25 \mathrm{~V} \\\mathrm{I}_{3}^{-}+2 \mathrm{e}^{-} \longrightarrow 3 \mathrm{I}^{-} & \mathscr{8}^{\circ}=+0.55 \mathrm{~V}\end{aligned}$$would you formulate this compound as thallium(III) iodide or thallium(I) triiodide?
How could you determine experimentally whether the compound $\mathrm{Ga}_{2} \mathrm{Cl}_{4}$ contains two gallium(II) ions or one gallium(I) and one gallium(III) ion? (Hint: Consider the electron configurations of the three possible ions.)
Tricalcium aluminate, an important component of Portland cement, is $44.4 \%$ calcium and $20.0 \%$ aluminum by mass. The remainder is oxygen.a. Calculate the empirical formula of tricalcium aluminate.b. The structure of tricalcium aluminate was not determineduntil 1975 . The aluminate anion $\left(\mathrm{Al}_{6} \mathrm{O}_{18}{ }^{18-}\right)$ has the following structure:What is the molecular formula of tricalcium aluminate?c. How would you describe the bonding in the $\mathrm{Al}_{6} \mathrm{O}_{18}{ }^{18-}$ anion?
In Exercise 107 in Chapter 5 , the pressure of $\mathrm{CO}_{2}$ in a bottle of sparkling wine was calculated assuming that the $\mathrm{CO}_{2}$ was insoluble in water. This was a bad assumption. Redo this problem by assuming $\mathrm{CO}_{2}$ obeys Henry's law. Use the data given in that problem to calculate the partial pressure of $\mathrm{CO}_{2}$ in the gas phase and the solubility of $\mathrm{CO}_{2}$ in the wine at $25^{\circ} \mathrm{C}$. The Henry's law constant for $\mathrm{CO}_{2}$ is $3.1 \times 10^{-2} \mathrm{~mol} / \mathrm{L} \cdot \mathrm{atm}$ at $25^{\circ} \mathrm{C}$ with Henry's law in theform $C=k P$, where $C$ is the concentration of the gas in $\mathrm{mol} / \mathrm{L}$.
The compound $\mathrm{Pb}_{3} \mathrm{O}_{4}$ (red lead) contains a mixture of lead(II) and lead(IV) oxidation states. What is the mole ratio of lead(II) to lead(IV) in $\mathrm{Pb}_{3} \mathrm{O}_{4}$ ?
Lead hydrogen arsenate, an inorganic insecticide used against the potato beetle, is produced by the following reaction:$$\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\mathrm{H}_{3} \mathrm{AsO}_{4}(a q) \rightarrow \mathrm{PbHAsO}_{4}(s)+\mathrm{HNO}_{3}(a q)$$Balance this equation.
Provide a reasonable estimate for the number of atoms in an average adult human. Explain your answer. Use the information given in Table $19.2 .$
Suppose $10.00 \mathrm{~g}$ of an alkaline earth metal reacts with $10.0 \mathrm{~L}$ of water to produce $6.10 \mathrm{~L}$ of hydrogen gas at $1.00 \mathrm{~atm}$ and $25^{\circ} \mathrm{C}$. Identify the metal and determine the $\mathrm{pH}$ of the solution.
Gallium arsenide, GaAs, has gained widespread use in semiconductor devices that convert light and electrical signals in fiberoptic communications systems. Gallium consists of $60 . \%^{69} \mathrm{Ga}$ and $40 . \%^{71} \mathrm{Ga}$. Arsenic has only one naturally occurring isotope, $^{75} \mathrm{As}$. Gallium arsenide is a polymeric material, but its mass spectrum shows fragments with the formulas $\mathrm{GaAs}$ and $\mathrm{Ga}_{2} \mathrm{As}_{2} .$ What would the distribution of peaks look like for these two fragments?
Consider dissolving $0.50 \mathrm{~mol}$ of $\mathrm{CO}_{2}(g)$ to enough water to make a $1.0$ -L solution. Determine the $\mathrm{pH}$ of this solution, and $\left[\mathrm{CO}_{3}{ }^{2-}\right]$. Use data from Appendix 5, Table $5.2 .$
a. Many biochemical reactions that occur in cells require relatively high concentrations of potassium ion $\left(\mathrm{K}^{+}\right)$. The concentration of $\mathrm{K}^{+}$ in muscle cells is about $0.15 \mathrm{M}$. The concentration of $\mathrm{K}^{+}$ in blood plasma is about $0.0050 M .$ The high internal concentration in cells is maintained by pumping $\mathrm{K}^{+}$ from the plasma. How much work must be done to transport $1.0 \mathrm{~mol}$ of $\mathrm{K}^{+}$ from the blood to the inside of a muscle cell at $37^{\circ} \mathrm{C}$ (normal body temperature)?b. When $1.0 \mathrm{~mol}$ of $\mathrm{K}^{+}$ is transferred from blood to the cells, do any other ions have to be transported? Why or why not?c. Cells use the hydrolysis of adenosine triphosphate, abbreviated ATP, as a source of energy. Symbolically, this reaction can be represented as$$\mathrm{ATP}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{ADP}(a q)+\mathrm{H}_{2} \mathrm{PO}_{4}^{-}(a q)$$where ADP represents adenosine diphosphate. For this reaction at $37^{\circ} \mathrm{C}, K=1.7 \times 10^{5} .$ How many moles of ATP must be hydrolyzed to provide the energy for the transport of $1.0 \mathrm{~mol}$ of $\mathrm{K}^{+}$ ? Assume standard conditions for the ATP hydrolysis reaction.
EDTA is used as a complexing agent in chemical analysis. Solutions of EDTA, usually containing the disodium salt $\mathrm{Na}_{2} \mathrm{H}_{2} \mathrm{EDTA}$, are also used to treat heavy metal poisoning. The equilibrium constant for the following reaction is $1.0 \times 10^{23}$.$$\mathrm{Pb}^{2+}(a q)+\mathrm{H}_{2} \mathrm{EDTA}^{2-}(a q) \rightleftharpoons \mathrm{PbEDTA}^{2-}(a q)+2 \mathrm{H}^{+}(a q)$$Calculate $\left[\mathrm{Pb}^{2+}\right]$ at equilibrium in a solution originally $0.0010 \mathrm{M}$ in $\mathrm{Pb}^{2+}, 0.050 M$ in $\mathrm{H}_{2} \mathrm{EDTA}^{2-}$, and buffered at $\mathrm{pH}=6.00$.
The compounds $\mathrm{CCl}_{4}$ and $\mathrm{H}_{2} \mathrm{O}$ do not react with each other. On the other hand, silicon tetrachloride reacts with water according to the equation$$\mathrm{SiCl}_{4}(l)+2 \mathrm{H}_{2} \mathrm{O}(I) \longrightarrow \mathrm{SiO}_{2}(s)+4 \mathrm{HCl}(a q)$$Discuss the importance of thermodynamics and kinetics in the reactivity of water with $\mathrm{SiCl}_{4}$ as compared with its lack of reactivity with $\mathrm{CCl}_{4}$.
One reason suggested to account for the instability of long chains of silicon atoms is that the decomposition involves the transition state shown below:The activation energy for such a process is $210 \mathrm{~kJ} / \mathrm{mol}$, which is less than either the $\mathrm{Si}-\mathrm{Si}$ or $\mathrm{Si}-\mathrm{H}$ energy. Why would a similar mechanism not be expected to be very important in the decomposition of long carbon chains?
From the information on the temperature stability of white and gray tin given in this chapter, which form would you expect to have the more ordered structure?
Lead forms compounds in the $+2$ and $+4$ oxidation states. All lead(II) halides are known (and are known to be ionic). Only $\mathrm{PbF}_{4}$ and $\mathrm{PbCl}_{4}$ are known among the possible lead(IV) halides. Presumably lead(IV) oxidizes bromide and iodide ions, producing the lead(II) halide and the free halogen:$$\mathrm{PbX}_{4} \longrightarrow \mathrm{Pb} \mathrm{X}_{2}+\mathrm{X}_{2}$$Suppose $25.00 \mathrm{~g}$ of a lead(IV) halide reacts to form $16.12 \mathrm{~g}$ of a lead(II) halide and the free halogen. Identify the halogen.
The heaviest member of the alkaline earth metals is radium (Ra), a naturally radioactive element discovered by Pierre and Marie Curie in 1898 . Radium was initially isolated from the uranium ore pitchblende, in which it is present as approximately $1.0 \mathrm{~g}$ per $7.0$ metric tons of pitchblende. How many atoms of radium can be isolated from $1.75 \times 10^{8} \mathrm{~g}$ of pitchblende ( 1 metric ton = $1000 \mathrm{~kg}$ )? One of the early uses of radium was as an additive to paint so that watch dials coated with this paint would glow in the dark. The longest-lived isotope of radium has a half-life of $1.60 \times 10^{3}$ years. If an antique watch, manufactured in 1925, contains $15.0 \mathrm{mg}$ of radium, how many atoms of radium will remain in 2025 ?
Indium(III) phosphide is a semiconducting material that has been frequently used in lasers, light-emitting diodes (LED) and fiber-optic devices. This material can be synthesized at $900 . \mathrm{K}$ according to the following reaction:$$\operatorname{In}\left(\mathrm{CH}_{3}\right)_{3}(g)+\mathrm{PH}_{3}(g) \longrightarrow \operatorname{InP}(s)+3 \mathrm{CH}_{4}(g)$$a. If $2.56 \mathrm{~L}$ of $\mathrm{In}\left(\mathrm{CH}_{3}\right)_{3}$ at $2.00 \mathrm{~atm}$ is allowed to react with $1.38 \mathrm{~L}$ of $\mathrm{PH}_{3}$ at $3.00 \mathrm{~atm}$, what mass of $\operatorname{In} \mathrm{P}(s)$ will be produced assuming the reaction is $87 \%$ efficient?b. When an electric current is passed through an optoelectronic device containing $\mathrm{InP}$, the light emitted has an energy of $2.03 \times 10^{-19} \mathrm{~J}$. What is the wavelength of this light and is it visible to the human eye?c. The semiconducting properties of InP can be altered by doping. If a small number of phosphorus atoms are replaced by atoms with an electron configuration of $[\mathrm{Kr}] 5 s^{2} 4 d^{10} 5 p^{4}$, is this n-type or p-type doping?
The chemistry of tin(II) fluoride is particularly complex and demonstrates a wide range of reactivities. For example, in aqueous solutions of tin(II) fluoride containing sodium fluoride, the predominant species is $\mathrm{SnF}_{3}^{-}$.a. What is the molecular geometry of $\mathrm{SnF}_{3}^{-}$ and the hybridization of the tin atom?b. When tin(II) fluoride is crystallized from aqueous solutions containing sodium fluoride, one of the products is the polyatomic cluster $\mathrm{Na}_{4} \mathrm{Sn}_{3} \mathrm{~F}_{10} .$ Write a balanced chemical reaction for the formation of $\mathrm{Na}_{4} \mathrm{Sn}_{3} \mathrm{~F}_{10}$ from tin(II) fluoride and NaF.c. Assuming complete conversion, what mass of $\mathrm{Na}_{4} \mathrm{Sn}_{3} \mathrm{~F}_{10}$ can be prepared by mixing $15.5 \mathrm{~mL}$ of $1.48 \mathrm{M}$ tin(II) fluoride with $35.0 \mathrm{~mL}$ of $1.25 \mathrm{M}$ NaF?
Use the symbols of the elements described in the following clues to fill in the blanks that spell out the name of a famous American scientist. Although this scientist was better known as a physicist than as a chemist, the Philadelphia institute that bears his name does include a biochemistry research facility.(1)(2)(3)(4)(5) (6)(7)(1) The oxide of this alkaline earth metal is amphoteric.(2) You might be surprised to learn that a binary compound of sodium with this element has the formula $\mathrm{NaX}_{3}$, a compound used in airbags.(3) This alkali metal is radioactive.(4) This element is the alkali metal with the least negative standard reduction potential. Write its symbol in reverse order.(5) Potash is an oxide of this alkali metal.(6) This is the only alkali metal that reacts directly with nitrogen to make a binary compound with formula $\mathrm{M}_{3} \mathrm{~N}$.(7) This element is the first in Group $3 \mathrm{~A}$ for which the $+1$ oxidation state is exhibited in stable compounds. Use only the second letter of its symbol.