Chapter 22

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) \(\mathrm{Ca}(\mathrm{CN})_{2}(s)+\operatorname{HBr}(a q) \longrightarrow\)

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) \(\mathrm{CuO}(s)+\mathrm{CO}(g) \longrightarrow\)

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) \(\mathrm{In}\) 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 14 element or of boron in each: (a) silane, \((\mathbf{b})\) germanium dichloride, (c) \(\operatorname{tin}(\mathrm{II})\) sulfide, \((\mathbf{d})\) sodium borohydride, \((\mathbf{e})\) lead(IV) nitrate, \((\mathbf{f})\) tin dioxide.

Write the formulas for the following compounds, and indicate the oxidation state of the group 14 element or of boron in each: (a) stannous fluoride, (b) germane, (c) diborane, (e) tin selenide, (d) tin(II) sulfate, (f) zinc carbonate.

Select the member of group 14 that best fits each description: \((\mathbf{a})\) has the greatest tendency to form multiple bonds with itself, (b) forms polymeric structures with oxygen, (c) is a metal with +2 and +4 oxidation states.

(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, \(\mathrm{Na}_{x} \mathrm{AlSi}_{3} \mathrm{O}_{8} .(\mathbf{b})\) Determine the number of hydroxide ions in the chemical formula of tremolite, \(\mathrm{Ca}_{2} \mathrm{Mg}_{5}\left(\mathrm{Si}_{4} \mathrm{O}_{11}\right)_{2}(\mathrm{OH})_{x}\).

(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"?

(a) How does the structure of diborane \(\left(\mathrm{B}_{2} \mathrm{H}_{6}\right)\) differ from that of ethane \(\left(\mathrm{C}_{2} \mathrm{H}_{6}\right) ?(\mathbf{b})\) 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"?

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. (e) \(2 \mathrm{H}_{3} \mathrm{PO}_{4}(l) \rightarrow \mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{7}(l)+\mathrm{H}_{2} \mathrm{O}(g)\) 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) \(\mathrm{PCl}_{5}(s),\) (b) \(\mathrm{CO}_{2}(g)\) (c) \(\mathrm{K}_{2} \mathrm{O}_{2}(s)\) (d) \(\mathrm{Mg}_{3} \mathrm{P}_{2}(s)\) (e) \(\operatorname{LiAlH}_{4}(s)\) (f) \(\mathrm{Cl}_{2} \mathrm{O}(g)\) (g) \(\mathrm{NO}_{2}(g)\)

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

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

A sulfuric acid plant produces a considerable amount of heat. This heat is used to generate electricity, which helps reduce operating costs. The synthesis of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) consists of three main chemical processes: (a) oxidation of \(S\) to \(\mathrm{SO}_{2}\), (b) oxidation of \(\mathrm{SO}_{2}\) to \(\mathrm{SO}_{3},\) (c) the dissolving of \(\mathrm{SO}_{3}\) in \(\mathrm{H}_{2} \mathrm{SO}_{4}\) and the subsequent reaction with water to form \(\mathrm{H}_{2} \mathrm{SO}_{4}\). If the third process produces \(130 \mathrm{~kJ} / \mathrm{mol}\), how much heat is produced in preparing a mole of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) from a mole of \(S\) ? How much heat is produced in preparing \(2000 \mathrm{~kg}\) of \(\mathrm{H}_{2} \mathrm{SO}_{4} ?\)

(a) What is the oxidation state of \(\mathrm{P}\) in \(\mathrm{PF}_{6}^{-}\) and of \(\mathrm{N}\) in \(\mathrm{NF}_{3} ?\) (b) Why doesn't \(\mathrm{N}\) form \(\mathrm{NF}_{6}^{-}\) 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 \(\mathrm{P}_{3} \mathrm{O}_{9}^{3-}\) and \(\mathrm{P}_{4} \mathrm{O}_{12}{\underline{\phantom{xx}}}^{4-}\) ions, respectively. Propose reasonable structures for these ions.

Write a balanced chemical reaction for the condensation reaction between \(\mathrm{H}_{3} \mathrm{PO}_{4}\), molecules to form \(\mathrm{H}_{6} \mathrm{P}_{4} \mathrm{O}_{13}\).

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 \(\mathrm{GeO}_{2}\).

When aluminum replaces up to half of the silicon atoms in \(\mathrm{SiO}_{2}\), a mineral class called feldspars result. The feldspars are the most abundant rock-forming minerals, comprising about \(50 \%\) of the minerals in Earth's crust. Orthoclase is a feldspar in which Al replaces one-fourth of the Si atoms of \(\mathrm{SiO}_{2},\) and charge balance is completed by \(\mathrm{K}^{+}\) ions. Determine the chemical formula for orthoclase.

Using \(\Delta G_{f}^{\circ}\) for \(\mathrm{NO}\) and \(\mathrm{NO}_{2},\) from Appendix \(\mathrm{C},\) calculate the equilibrium constant for the oxidation of \(\mathrm{NO}\) to \(\mathrm{NO}_{2}\) at \(298.0 \mathrm{~K}\) as described in equation \(22.38 .\)

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 scrubbing with an alkali solid such as calcium carbonate to form calcium sulfite and carbon dioxide gas. (a) Write a balanced chemical equation for the reaction. (b) What mass of \(\mathrm{CaCO}_{3}\) would be required to remove the \(\mathrm{SO}_{2}\) formed by burning \(1000 \mathrm{~kg}\) of coal containing \(8.0 \% \mathrm{~S}\) by mass? (c) What volume of \(\mathrm{CO}_{2}\) is formed under standard temperature and pressure? Assume that all reactions are \(100 \%\) efficient.

The maximum allowable concentration of \(\mathrm{H}_{2} \mathrm{~S}(g)\) 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 \(101.3 \mathrm{kPa}\) and \(25^{\circ} \mathrm{C}\) in an average room measuring \(3.5 \mathrm{~m} \times 6.0 \mathrm{~m} \times 2.5 \mathrm{~m} ?\) (Under these conditions, the average molar mass of air is \(29.0 \mathrm{~g} / \mathrm{mol} .)\)

The standard heats of formation of \(\mathrm{H}_{2} \mathrm{O}(g), \mathrm{H}_{2} \mathrm{~S}(g), \mathrm{H}_{2} \operatorname{Se}(g)\), 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 \(\mathrm{O}, \mathrm{S}\), 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 \(\mathrm{MnSi}\) 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 \(\mathrm{MnSi}\) to be: metallic, molecular, covalent-network, or ionic? (b) Write a likely balanced chemical equation for the reaction of MnSi with concentrated aqueous \(\mathrm{HF}\).

Nitric acid is a powerful oxidizing agent. Using standard reduction potentials, predict whether the following metals can be oxidized to +2 ions by nitric acid: (a) iron, (b) copper, (c) rhodium, (d) zinc, (e) lead, (f) tin.

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.)

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?