Chapter 22

Write a balanced net ionic equation for each of the following reactions: (a) Dilute nitric acid reacts with zinc metal with formation of nitrous oxide. (b) Concentrated nitric acid reacts with sulfur with formation of nitrogen dioxide. (c) Concentrated nitric acid oxidizes sulfur dioxide with formation of nitric oxide. (d) Hydrazine is burned in excess fluorine gas, forming \(\mathrm{NF}_{3}\). (e) Hydrazine reduces \(\mathrm{CrO}_{4}{\underline{\phantom{xx}}}^{2-}\) to \(\mathrm{Cr}(\mathrm{OH})_{4}{\underline{\phantom{xx}}}^{-}\)in base (hydrazine is oxidized to \(\mathrm{N}_{2}\) ).

Write complete balanced half-reactions for (a) oxidation of nitrous acid to nitrate ion in acidic solution, (b) oxidation of \(\mathrm{N}_{2}\) to \(\mathrm{N}_{2} \mathrm{O}\) in acidic solution.

Write complete balanced half-reactions for (a) reduction of nitrate ion to \(\mathrm{NO}\) in acidic solution, (b) oxidation of \(\mathrm{HNO}_{2}\) to \(\mathrm{NO}_{2}\) in acidic solution.

Write a molecular formula for each compound, and indicate the oxidation state of the group \(5 \mathrm{~A}\) element in each formula: (a) phosphorous acid, (b) pyrophosphoric acid, (c) antimony trichloride, (d) magnesium arsenide, (e) diphosphorus pentoxide, (f) sodium phosphate.

Write a chemical formula for each compound or ion, and indicate the oxidation state of the group \(5 \mathrm{~A}\) element in each formula: (a) phosphate ion, (b) arsenous acid, (c) antimony(III) sulfide, (d) calcium dihydrogen phosphate, (e) potassium phosphide, (f) gallium arsenide.

Account for the following observations: (a) Phosphorus forms a pentachloride, but nitrogen does not. (b) \(\mathrm{H}_{3} \mathrm{PO}_{2}\) is a monoprotic acid. (c) Phosphonium salts, such as \(\mathrm{PH}_{4} \mathrm{Cl}\), can be formed under anhydrous conditions, but they cannot be made in aqueous solution. (d) White phosphorus is more reactive than red phosphorus.

Account for the following observations: (a) \(\mathrm{H}_{3} \mathrm{PO}_{3}\) is a diprotic acid. (b) Nitric acid is a strong acid, whereas phosphoric acid is weak. (c) Phosphate rock is ineffective as a phosphate fertilizer. (d) Phosphorus does not exist at room temperature as diatomic molecules, but nitrogen does. (e) Solutions of \(\mathrm{Na}_{3} \mathrm{PO}_{4}\) are quite basic.

Write a balanced equation for each of the following reactions: (a) preparation of white phosphorus from calcium phosphate, (b) hydrolysis of \(\mathrm{PBr}_{3}\), (c) reduction of \(\mathrm{PBr}_{3}\) to \(\mathrm{P}_{4}\) in the gas phase, using \(\mathrm{H}_{2}\).

Write a balanced equation for each of the following reactions: (a) hydrolysis of \(\mathrm{PCl}_{5}\) (b) dehydration of phosphoric acid (also called orthophosphoric acid) to form pyrophosphoric acid, (c) reaction of \(\mathrm{P}_{4} \mathrm{O}_{10}\) with water. Carbon, the Other Group 4A Elements, and Boron (Sections 22.9, 22.10, and 22.11)

Give the chemical formula for (a) hydrocyanic acid, (b) nickel tetracarbonyl, (c) barium bicarbonate, (d) calcium acetylide, (e) potassium carbonate.

Give the chemical formula for (a) carbonic acid, (b) sodium cyanide, (c) potassium hydrogen carbonate, (d) acetylene, (e) iron pentacarbonyl.

Complete and balance the following equations: (a) \(\mathrm{ZnCO}_{3}(s) \stackrel{\Delta}{\longrightarrow}\) (b) \(\mathrm{BaC}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow\) (c) \(\mathrm{C}_{2} \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow\) (d) \(\mathrm{CS}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow\) (e) \(\mathrm{Ca}(\mathrm{CN})_{2}(s)+\operatorname{HBr}(a q)\)

Complete and balance the following equations: (a) \(\mathrm{CO}_{2}(g)+\mathrm{OH}^{-}(a q) \longrightarrow\) (b) \(\mathrm{NaHCO}_{3}(s)+\mathrm{H}^{+}(a q) \longrightarrow\) (c) \(\mathrm{CaO}(s)+\mathrm{C}(s) \stackrel{\Delta}{\longrightarrow}\) (d) \(\mathrm{C}(s)+\mathrm{H}_{2} \mathrm{O}(g) \stackrel{\Delta}{\longrightarrow}\) (e) \(\mathrm{CuO}(s)+\mathrm{CO}(g)\)

Write a balanced equation for each of the following reactions: (a) Hydrogen cyanide is formed commercially by passing a mixture of methane, ammonia, and air over a catalyst at \(800^{\circ} \mathrm{C}\). Water is a by-product of the reaction. (b) Baking soda reacts with acids to produce carbon dioxide gas. (c) When barium carbonate reacts in air with sulfur dioxide, barium sulfate and carbon dioxide form.

Write a balanced equation for each of the following reactions: (a) Burning magnesium metal in a carbon dioxide atmosphere reduces the \(\mathrm{CO}_{2}\) to carbon. (b) In photosynthesis, solar energy is used to produce glucose \(\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)\) and \(\mathrm{O}_{2}\) from carbon dioxide and water. (c) When carbonate salts dissolve in water, they produce basic solutions.

Write the formulas for the following compounds, and indicate the oxidation state of the group 4A element or of boron in each: (a) boric acid, (b) silicon tetrabromide, (c) lead(II) chloride, (d) sodium tetraborate decahydrate (borax), (e) boric oxide, (f) germanium dioxide.

Write the formulas for the following compounds, and indicate the oxidation state of the group \(4 \mathrm{~A}\) element or of boron in each: (a) silicon dioxide, (b) germanium tetrachloride, (c) sodium borohydride, (d) stannous chloride, (e) diborane, (f) boron trichloride.

Select the member of group \(4 \mathrm{~A}\) that best fits each description: (a) has the lowest first ionization energy, (b) is found in oxidation states ranging from \(-4\) to \(+4\), (c) is most abundant in Earth's crust.

Select the member of group \(4 \mathrm{~A}\) that best fits each description: (a) forms chains to the greatest extent, (b) forms the most basic oxide, (c) is a metalloid that can form \(2+\) ions.

(a) What is the characteristic geometry about silicon in all silicate minerals? (b) Metasilicic acid has the empirical formula \(\mathrm{H}_{2} \mathrm{SiO}_{3}\). Which of the structures shown in Figure \(22.34\) would you expect metasilicic acid to have? 22.76 Speculate as to why carbon forms carbonate rather than silicate analogs.

(a) Determine the number of calcium ions in the chemical formula of the mineral hardystonite, \(\mathrm{Ca}_{x} \mathrm{Zn}\left(\mathrm{Si}_{2} \mathrm{O}_{7}\right)\). (b) Determine the number of hydroxide ions in the chemical formula of the mineral pyrophyllite, \(\mathrm{Al}_{2}\left(\mathrm{Si}_{2} \mathrm{O}_{5}\right)_{2}(\mathrm{OH})_{x}\).

a) Determine the number of sodium ions in the chemical formula of albite, \(\mathrm{Na}_{x} \mathrm{AlSi}_{3} \mathrm{O}_{g}\). (b) Determine the number of hydroxide ions in the chemical formula of tremolite, \(\mathrm{Ca}_{2} \mathrm{Mg}_{5}\left(\mathrm{Si}_{4} \mathrm{O}_{11}\right)_{2}(\mathrm{OH})_{\mathrm{x}}\) -

(a) How does the structure of diborane \(\left(\mathrm{B}_{2} \mathrm{H}_{6}\right)\) differ from that of ethane \(\left(\mathrm{C}_{2} \mathrm{H}_{6}\right)\) ? (b) Explain why diborane adopts the geometry that it does. (c) What is the significance of the statement that the hydrogen atoms in diborane are described as "hydridic"?

Write a balanced equation for each of the following reactions: (a) Diborane reacts with water to form boric acid and molecular hydrogen. (b) Upon heating, boric acid undergoes a condensation reaction to form tetraboric acid. (c) Boron oxide dissolves in water to give a solution of boric acid.

Indicate whether each of the following statements is true or false (a) \(\mathrm{H}_{2}(g)\) and \(\mathrm{D}_{2}(g)\) are allotropic forms of hydrogen. (b) \(\mathrm{ClF}_{3}\) is an interhalogen compound. (c) \(\mathrm{MgO}(\) s) is an acidic anhydride. (d) \(\mathrm{SO}_{2}(g)\) is an acidic anhydride. (c) \(2 \mathrm{H}_{3} \mathrm{PO}_{4}(l) \rightarrow \mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{7}(l)+\mathrm{H}_{2} \mathrm{O}(g)\) is an example of a condensation reaction. (f) Tritium is an isotope of the element hydrogen. (g) \(2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{SO}_{3}(g)\) is an example of a disproportionation reaction.

Although the \(\mathrm{ClO}_{4}^{-}\)and \(\mathrm{IO}_{4}^{-}\)ions have been known for a long time, \(\mathrm{BrO}_{4}^{-}\)was not synthesized until 1965 . The ion was synthesized by oxidizing the bromate ion with xenon difluoride, producing xenon, hydrofluoric acid, and the perbromate ion. (a) Write the balanced equation for this reaction. (b) What are the oxidation states of Br in the Br-containing species in this reaction?

Write a balanced equation for the reaction of each of the following compounds with water: (a) \(\mathrm{SO}_{2}(g)\), (b) \(\mathrm{Cl}_{2} \mathrm{O}_{7}(g)\), (c) \(\mathrm{Na}_{2} \mathrm{O}_{2}(s)\), (d) \(\mathrm{BaC}_{2}\) (s), (e) \(\mathrm{RbO}_{2}\) (s) (f) \(\mathrm{Mg}_{3} \mathrm{~N}_{2}(s)\), (g) \(\mathrm{NaH}(\) s).

What is the anhydride for each of the following acids: (a) \(\mathrm{H}_{2} \mathrm{SO}_{4}\), (b) \(\mathrm{HClO}_{3}\), (c) \(\mathrm{HNO}_{2}\), (d) \(\mathrm{H}_{2} \mathrm{CO}_{3}\), (e) \(\mathrm{H}_{3} \mathrm{PO}_{4}\) ?

Hydrogen peroxide is capable of oxidizing (a) hydrazine to \(\mathrm{N}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\), (b) \(\mathrm{SO}_{2}\) to \(\mathrm{SO}_{4}^{2-}\), (c) \(\mathrm{NO}_{2}^{-}\)to \(\mathrm{NO}_{3}^{-}\), (d) \(\mathrm{H}_{2} \mathrm{~S}(\mathrm{~g})\) to \(\mathrm{S}(s)\), (e) \(\mathrm{Fe}^{2+}\) to \(\mathrm{Fe}^{3+}\). Write a balanced net ionic equation for each of these redox reactions.

Explain why \(\mathrm{SO}_{2}\) can be used as a reducing agent but \(\mathrm{SO}_{3}\) cannot.

(a) What is the oxidation state of \(\mathrm{P}\) in \(\mathrm{PO}_{4}{\underline{\phantom{xx}}}^{3-}\) and of \(\mathrm{N}^{-}\)in \(\mathrm{NO}_{3}{\underline{\phantom{xx}}}^{-}\)? (b) Why doesn't N form a stable \(\mathrm{NO}_{4}^{3-}\). ion analogous to \(\mathrm{P}\) ?

(a) The \(\mathrm{P}_{4}, \mathrm{P}_{4} \mathrm{O}_{6}\) and \(\mathrm{P}_{4} \mathrm{O}_{10}\) molecules have a common structural feature of four \(\mathrm{P}\) atoms arranged in a tetrahedron (Figures \(22.27\) and 22.28). Does this mean that the bonding between the \(\mathrm{P}\) atoms is the same in all these cases? Explain. (b) Sodium trimetaphosphate \(\left(\mathrm{Na}_{3} \mathrm{P}_{3} \mathrm{O}_{9}\right)\) and sodium tetrametaphosphate \(\left(\mathrm{Na}_{4} \mathrm{P}_{4} \mathrm{O}_{12}\right)\) are used as water-softening agents. They contain cyclic \(\mathrm{P}_{3} \mathrm{O}_{9}{\underline{\phantom{xx}}}^{3-}\) and \(\mathrm{P}_{4} \mathrm{O}_{12}{\underline{\phantom{xx}}}^{4-}\) ions, respectively. Propose reasonable structures for these ions.

Ultrapure germanium, like silicon, is used in semiconductors. Germanium of "ordinary" purity is prepared by the high-temperature reduction of \(\mathrm{GeO}_{2}\) with carbon. The Ge is converted to \(\mathrm{GeCl}_{4}\) by treatment with \(\mathrm{Cl}_{2}\) and then purified by distillation; \(\mathrm{GeCl}_{4}\) is then hydrolyzed in water to \(\mathrm{GeO}_{2}\) and reduced to the elemental form with \(\mathrm{H}_{2}\). The element is then zone refined. Write a balanced chemical equation for each of the chemical transformations in the course of forming ultrapure Ge from \(\mathrm{GeO}_{2}\).

(a) Determine the charge of the aluminosilicate ion whose composition is \(\mathrm{AlSi}_{3} \mathrm{O}_{10}\). (b) Using Figure \(22.33\), propose a reasonable description of the structure of this aluminosilicate.

The solubility of \(\mathrm{Cl}_{2}\) in \(100 \mathrm{~g}\) of water at \(\mathrm{STP}\) is \(310 \mathrm{~cm}^{3}\). Assume that this quantity of \(\mathrm{Cl}_{2}\) is dissolved and equilibrated as follows: $$ \mathrm{Cl}_{2}(a q)+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{Cl}^{-}(a q)+\mathrm{HClO}(a q)+\mathrm{H}^{+}(a q) $$ (a) If the equilibrium constant for this reaction is \(4.7 \times 10^{-4}\), calculate the equilibrium concentration of \(\mathrm{HClO}\) formed. (b) What is the \(\mathrm{pH}\) of the final solution?

The dissolved oxygen present in any highly pressurized, high-temperature steam boiler can be extremely corrosive to its metal parts. Hydrazine, which is completely miscible with water, can be added to remove oxygen by reacting with it to form nitrogen and water. (a) Write the balanced equation for the reaction between gaseous hydrazine and oxygen. (b) Calculate the enthalpy change accompanying this reaction. (c) Oxygen in air dissolves in water to the extent of \(9.1\) Ppm at \(20^{\circ} \mathrm{C}\) at sea level. How many grams of hydrazine are required to react with all the oxygen in \(3.0 \times 10^{4} \mathrm{~L}\) (the volume of a small swimming pool) under these conditions?

One method proposed for removing \(\mathrm{SO}_{2}\) from the flue gases of power plants involves reaction with aqueous \(\mathrm{H}_{2} \mathrm{~S}\). Elemental sulfur is the product. (a) Write a balanced chemical equation for the reaction. (b) What volume of \(\mathrm{H}_{2} \mathrm{~S}\) at \(27^{\circ} \mathrm{C}\) and 760 torr would be required to remove the \(\mathrm{SO}_{2}\) formed by burning \(2.0\) tons of coal containing \(3.5 \% \mathrm{~S}\) by mass? (c) What mass of elemental sulfur is produced? Assume that all reactions are \(100 \%\) efficient.

The maximum allowable concentration of \(\mathrm{H}_{2} \mathrm{~S}(\mathrm{~g})\) in air is \(20 \mathrm{mg}\) per kilogram of air (20 ppm by mass). How many grams of FeS would be required to react with hydrochloric acid to produce this concentration at \(1.00\) atm and \(25^{\circ} \mathrm{C}\) in an average room measuring \(12 \mathrm{ft} \times 20 \mathrm{ft} \times 8 \mathrm{ft}\) ? (Under these conditions, the average molar mass of air is \(29.0 \mathrm{~g} / \mathrm{mol}\).)

The standard heats of formation of \(\mathrm{H}_{2} \mathrm{O}(g), \mathrm{H}_{2} \mathrm{~S}(g), \mathrm{H}_{2} \mathrm{Se}(g)\), and \(\mathrm{H}_{2} \mathrm{Te}(g)\) are \(-241.8,-20.17,+29.7\), and \(+99.6 \mathrm{~kJ} /\) mol, respectively. The enthalpies necessary to convert the elements in their standard states to one mole of gaseous atoms are \(248,277,227\), and \(197 \mathrm{~kJ} / \mathrm{mol}\) of atoms for \(\mathrm{O}, \mathrm{S}, \mathrm{Se}\), and Te, respectively. The enthalpy for dissociation of \(\mathrm{H}_{2}\) is \(436 \mathrm{~kJ} / \mathrm{mol}\). Calculate the average \(\mathrm{H}-\mathrm{O}, \mathrm{H}-\mathrm{S}, \mathrm{H}-\mathrm{Se}\), and \(\mathrm{H}\) - Te bond enthalpies, and comment on their trend.

Manganese silicide has the empirical formula MnSi and melts at \(1280^{\circ} \mathrm{C}\). It is insoluble in water but does dissolve in aqueous HF. (a) What type of compound do you expect MnSi to be: metallic, molecular, covalent- network, or ionic? (b) Write a likely balanced chemical equation for the reaction of \(\mathrm{MnSi}\) with concentrated aqueous HF.

Chemists tried for a long time to make molecular compounds containing silicon- silicon double bonds, they finally succeeded in 1981 . The trick is having large, bulky R groups on the silicon atoms to make \(\mathrm{R}_{2} \mathrm{Si}=\mathrm{SiR}_{2}\) compounds. What experiments could you do to prove that a new compound has a silicon-silicon double bond rather than a silicon-silicon single bond?

Hydrazine has been employed as a reducing agent for metals. Using standard reduction potentials, predict whether the following metals can be reduced to the metallic state by hydrazine under standard conditions in acidic solution: (a) \(\mathrm{Fe}^{2+}\), (b) \(\mathrm{Sn}^{2+}\), (c) \(\mathrm{Cu}^{2+}\), (d) \(\mathrm{Ag}^{+}\), (e) \(\mathrm{Cr}^{3+}\), (f) \(\mathrm{Co}^{3+}\).

Both dimethylhydrazine, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NNH}_{2}\), and methylhydrazine, \(\mathrm{CH}_{3} \mathrm{NHNH}_{2}\), have been used as rocket fuels. When dinitrogen tetroxide \(\left(\mathrm{N}_{2} \mathrm{O}_{4}\right)\) is used as the oxidizer, the products are \(\mathrm{H}_{2} \mathrm{O}, \mathrm{CO}_{2}\), and \(\mathrm{N}_{2}\). If the thrust of the rocket depends on the volume of the products produced, which of the substituted hydrazines produces a greater thrust per gram total mass of oxidizer plus fuel? (Assume that both fuels generate the same temperature and that \(\mathrm{H}_{2} \mathrm{O}(g)\) is formed.)

Carbon forms an unusual unstable oxide of formula \(\mathrm{C}_{3} \mathrm{O}_{2}\), called carbon suboxide. Carbon suboxide is made by using \(\mathrm{P}_{2} \mathrm{O}_{5}\) to dehydrate the dicarboxylic acid called malonic acid, which has the formula \(\mathrm{HOOC}-\mathrm{CH}_{2}-\mathrm{COOH}\). (a) Write a balanced reaction for the production of carbon suboxide from malonic acid. (b) How many grams of carbon suboxide could be made from \(20.00 \mathrm{~g}\) of malonic acid? (c) Suggest a Lewis structure for \(\mathrm{C}_{3} \mathrm{O}_{2}\) - (Hint: The Lewis structure of malonic acid suggests which atoms are connected to which.) (d) By using the information in Table 8.5, predict the \(\mathrm{C}-\mathrm{C}\) and \(\mathrm{C}-\mathrm{O}\) bond lengths in \(\mathrm{C}_{3} \mathrm{O}_{2}\). (e) Sketch the Lewis structure of a product that could result by the addition of \(2 \mathrm{~mol}\) of \(\mathrm{H}_{2}\) to \(1 \mathrm{~mol}\) of \(\mathrm{C}_{3} \mathrm{O}_{2}\) -

Borazine, \((\mathrm{BH})_{3}(\mathrm{NH})_{3}\), is an analog of \(\mathrm{C}_{6} \mathrm{H}_{6}\), benzene. It can be prepared from the reaction of diborane with ammonia, with hydrogen as another product; or from lithium borohydride and ammonium chloride, with lithium chloride and hydrogen as the other products. (a) Write balanced chemical equations for the production of borazine using both synthetic methods. (b) Draw the Lewis dot structure of borazine. (c) How many grams of borazine can be prepared from \(2.00 \mathrm{~L}\) of ammonia at STP, assuming diborane is in excess?