Chapter 21

Sulfur forms anionic chains of S atoms called polysulfides. Draw a Lewis electron dot structure for the \(S_{2}^{2-}\) ion. The \(S_{2}^{2-}\) ion is the disulfide ion, an analogue of the peroxide ion. It occurs in iron pyrites, \(\mathrm{FeS}_{2}\)

Sulfur forms a range of compounds with fluorine. Draw Lewis electron dot structures for \(\mathrm{S}_{2} \mathrm{F}_{2}\) (connectivity is FSSF), \(\mathrm{SF}_{2}, \mathrm{SF}_{4}, \mathrm{SF}_{6},\) and \(\mathrm{S}_{2} \mathrm{F}_{10} .\) What is the oxidation number of sulfur in each of these compounds?

Which halogen has the highest bond dissociation enthalpy? (a) \(\mathrm{F}_{2}\) (b) \(\mathrm{Cl}_{2}\) (c) \(\mathrm{Br}_{2}\) (d) \(\mathrm{I}_{2}\)

Which of the following statements is not correct? (a) The ease of oxidation of the halide ions is \(\mathrm{F}^{-}\) $$ <\mathrm{Cl}^{-}<\mathrm{Br}^{-}<\mathrm{I}^{-} $$ (b) Fluorine is the most abundant halogen in the Earth's crust. (c) \(\mathrm{F}_{2}\) is prepared industrially by electrolysis of aqueous NaF. (d) HF is used to etch glass.

Halogens combine with one another to produce interhalogens such as BrF \(_{3}\). Sketch a possible molecular structure for this molecule, and decide if the \(\mathrm{F}-\mathrm{Br}-\mathrm{F}\) bond angles will be less than or greater than ideal.

In which of the following species is Xe in the +4 oxidation state? (a) \(\mathrm{XeOF}_{4}\) (c) \(\mathrm{XeF}_{3}^{+}\) (b) \(\mathrm{Xe}_{2} \mathrm{F}_{3}^{+}\) (d) \(\mathrm{XeO}_{6}^{4-}\)

Predict the electron pair geometry for the xenon atom in \(\mathrm{XeOF}_{4}\) (a) linear (b) trigonal bipyramid (c) trigonal planar (d) octahedral (e) tetrahedral

Draw the Lewis electron dot structure for \(\mathrm{XeO}_{3} \mathrm{F}_{2}\) What is its electron-pair geometry and its molecular geometry?

Argon is present in dry air to the extent of \(0.93 \%\) by volume. What quantity of argon is present in \(1.00 \mathrm{L}\) of air? If you wanted to isolate 1.00 mol of argon, what volume of air would you need at 1.00 atm pressure and \(25^{\circ} \mathrm{C} ?\)

For each of the third-period elements (Na through Ar), identify the following: (a) whether the element is a metal, nonmetal, or metalloid (b) the color and appearance of the element (c) the state of the element \((s, \ell, \text { or } g\) ) under standard conditions

Consider the chemistries of \(\mathrm{C}, \mathrm{Si}, \mathrm{Ge},\) and \(\mathrm{Sn}\). (a) Write a balanced chemical equation to depict the reaction of each element with elemental chlorine. (b) Describe the bonding in each of the products of the reactions with chlorine as ionic or covalent. (c) Compare the reactions, if any, of some Group 4A chlorides - \(\mathrm{CCl}_{4}, \mathrm{SiCl}_{4}\), and \(\mathrm{SnCl}_{4}-\) with water.

Consider the chemistries of the elements potassium, calcium, gallium, germanium, and arsenic. (a) Write a balanced chemical equation depicting the reaction of each element with elemental chlorine. (b) Describe the bonding in each of the products of the reactions with chlorine as ionic or covalent. (c) Draw Lewis electron dot structures for the products of the reactions of gallium and arsenic with chlorine. What are their electronpair and molecular geometries?

When \(\mathrm{BCl}_{3}\) gas is passed through an electric discharge, small amounts of the reactive molecule \(\mathrm{B}_{2} \mathrm{Cl}_{4}\) are produced. (The molecule has a \(\mathrm{B}-\mathrm{B}\) covalent bond.) (a) Draw a Lewis electron dot structure for \(\mathrm{B}_{2} \mathrm{Cl}_{4}\) (b) Describe the hybridization of the B atoms in the molecule and the geometry around each B atom.

Complete and balance the following equations. (a) \(\mathrm{KClO}_{3}+\) heat \(\rightarrow\) (b) \(\mathrm{H}_{2} \mathrm{S}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow\) (c) \(\mathrm{Na}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow\) (d) \(\mathrm{P}_{4}(\mathrm{s})+\mathrm{KOH}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\ell) \rightarrow\) (e) \(\mathrm{NH}_{4} \mathrm{NO}_{3}(\mathrm{s})+\) heat \(\rightarrow\) (f) \(\operatorname{In}(\mathrm{s})+\mathrm{Br}_{2}(\ell) \rightarrow\) (g) \(\operatorname{SnCl}_{4}(\ell)+\mathrm{H}_{2} \mathrm{O}(\ell) \rightarrow\)

(a) Heating barium oxide in pure oxygen gives barium peroxide. Write a balanced equation for this reaction. (b) Barium peroxide is an excellent oxidizing agent. Write a balanced equation for the reaction of iron with barium peroxide to give iron(III) oxide and barium oxide.

Worldwide production of silicon carbide, \(\mathrm{SiC},\) is several hundred thousand tons annually. If you want to produce \(1.0 \times 10^{5}\) metric tons of \(\mathrm{SiC}\) what mass (metric tons) of silicon sand \(\left(\mathrm{SiO}_{2}\right)\) will you use if \(70 \%\) of the sand is converted to SiC? (A metric ton is exactly \(1000 \mathrm{kg} .\) )

To store \(2.88 \mathrm{kg}\) of gasoline with an energy equivalence of \(1.43 \times 10^{8} \mathrm{J}\) requires a volume of \(4.1 \mathrm{L}\) In comparison, 1.0 kg of \(\mathrm{H}_{2}\) has the same energy equivalence. What volume is required if this quantity of \(\mathrm{H}_{2}\) is to be stored at \(25^{\circ} \mathrm{C}\) and 1.0 atm of pressure?

Halogens form polyhalide ions. Sketch Lewis electron dot structures and molecular structures for the following ions: (a) \(\mathrm{I}_{3}^{-}\) (b) \(\mathrm{BrCl}_{2}^{-}\) (c) \(\mathrm{ClF}_{2}^{+}\) (d) An iodide ion and two iodine molecules form the \(\mathrm{I}_{5}^{-}\) ion. Here, the ion has five I atoms in a row, but the ion is not linear. Draw the Lewis dot structure for the ion, and propose a structure for the ion.

Calcium fluoride can be used in the fluoridation of municipal water supplies. If you want to achieve a fluoride ion concentration of \(2.0 \times 10^{-5} \mathrm{M},\) what mass of \(\mathrm{CaF}_{2}\) must you use for \(1.0 \times 10^{6}\) L of water? \(\left(K_{s p} \text { for } \operatorname{CaF}_{2}\) is \right. \(\left.5.3 \times 10^{-11} .\right)\)

The steering rockets in space vehicles use \(\mathrm{N}_{2} \mathrm{O}_{4}\) and a derivative of hydrazine, 1,1 -dimethylhydrazine (Study Question \(5.86) .\) This mixture is called a hypergolic fuel because it ignites when the reactants come into contact: $$\begin{aligned} \mathrm{H}_{2} \mathrm{NN}\left(\mathrm{CH}_{3}\right)_{2}(\ell)+2 \mathrm{N}_{2} \mathrm{O}_{4}(\ell) & \rightarrow \\ 3 \mathrm{N}_{2}(\mathrm{g})+& 4 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+2 \mathrm{CO}_{2}(\mathrm{g}) \end{aligned}$$ (a) Identify the oxidizing agent and the reducing agent in this reaction. (b) The same propulsion system was used by the Lunar Lander on moon missions in the 1970 s. If the Lander used \(4100 \mathrm{kg}\) of \(\mathrm{H}_{2} \mathrm{NN}\left(\mathrm{CH}_{3}\right)_{2}\) what mass (in kilograms) of \(\mathrm{N}_{2} \mathrm{O}_{4}\) was required to react with it? What mass (in kilograms) of each of the reaction products was generated?

Phosphorus forms an extensive series of Oxoanions. (a) Draw a structure, and give the charge for an oxophosphate anion with the formula \(\left[\mathrm{P}_{4} \mathrm{O}_{13}\right]^{\mathrm{n}-} .\) How many ionizable \(\mathrm{H}\) atoms should the completely protonated acid have? (b) Draw a structure, and give the charge for a cyclic oxophosphate anion with the formula \(\left[\mathrm{P}_{4} \mathrm{O}_{12}\right]^{\mathrm{n}-} .\) How many ionizable H atoms should the completely protonated acid have?

In \(1774,\) C. Scheele obtained a gas by reacting pyrolusite \(\left(\mathrm{MnO}_{2}\right)\) with sulfuric acid. The gas, which had been obtained that same year by Joseph Priestley by a different method, was an element, A. (a) What is the element isolated by Scheele and Priestley? (b) Element A combines with almost all other elements. For example, with cesium it gives a compound in which the mass percent of A is \(19.39 \%\). The element combines with hydrogen to give a compound with a mass percent of element A of 94.12\%. Determine the formulas of the cesium and hydrogen compounds. (c) The compounds of cesium and hydrogen with element A react with one another. Write a balanced equation for the reaction.

When palladium metal is exposed to \(\mathrm{H}_{2}\) gas, the metal become brittle because \(\mathrm{H}_{2}\) molecules dissociate and \(\mathrm{H}\) atoms fill some of the octahedral holes in the face-centered cubic lattice. To find the value of \(x\) in the formula \(\mathrm{PdH}_{x}\), you perform the following experiment: \(\mathrm{H}_{2}\) gas in a 2.25 -L flask has a pressure of \(113 \mathrm{mm}\) at \(23.0^{\circ} \mathrm{C}\). After exposing the gas to \(0.192 \mathrm{g}\) of \(\mathrm{Pd},\) the pressure is now \(108 \mathrm{mm}\) at \(23^{\circ} \mathrm{C} .\) What is the value of \(\mathrm{x}\) in \(\mathrm{PdH}_{x} ?\)

The chemistry of gallium: (a) Gallium hydroxide, like aluminum hydroxide, is amphoteric. Write a balanced equation to show how this hydroxide can dissolve in both HCl(aq) and NaOH(aq). (b) Gallium ion in water, \(\mathrm{Ga}^{3+}(\mathrm{aq}),\) has a \(K_{\mathrm{a}}\) value of \(1.2 \times 10^{-3} .\) Is this ion a stronger or a weaker acid than \(\mathrm{Al}^{3+}(\mathrm{aq}) ?\)

Silicon-oxygen rings are a common structural feature in silicate chemistry. Draw the structure for the anion \(\left[\mathrm{Si}_{3} \mathrm{O}_{9}\right]^{6-},\) which is found in minerals such as benitoite. Is the ring expected to be planar?

One material needed to make silicones is dichlorodimethylsilane, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{SiCl}_{2} .\) It is made by treating silicon powder at about \(300^{\circ} \mathrm{C}\) with \(\mathrm{CH}_{3} \mathrm{Cl}\) in the presence of a copper-containing catalyst. (a) Write a balanced equation for the reaction. (b) Assume you carry out the reaction on a small scale with \(2.65 \mathrm{g}\) of silicon. To measure the \(\mathrm{CH}_{3} \mathrm{Cl}\) gas, you fill a \(5.60-\mathrm{L}\) flask at \(24.5^{\circ} \mathrm{C}\) What pressure of \(\mathrm{CH}_{3} \mathrm{Cl}\) gas must you have in the flask to have the stoichiometrically correct amount of the compound? (c) What mass of \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{SiCl}_{2}\) can be produced from \(2.65 \mathrm{g}\) of \(\mathrm{Si}\) and excess \(\mathrm{CH}_{3} \mathrm{Cl} ?\)

Sodium borohydride, NaBH_, reduces many metal ions to the metal. (a) Write a balanced equation for the reaction of \(\mathrm{NaBH}_{4}\) with \(\mathrm{AgNO}_{3}\) in water to give silver metal, \(\mathrm{H}_{2}\) gas, boric acid, and sodium nitrate. (The chemistry of \(\mathrm{NaBH}_{4}\) is described in Section 21.6.) (b) What mass of silver can be produced from \(575 \mathrm{mL}\) of \(0.011 \mathrm{M} \mathrm{AgNO}_{3}\) and \(13.0 \mathrm{g}\) of \(\mathrm{NaBH}_{4} ?\)

When \(1.00 \mathrm{g}\) of a white solid \(\mathrm{A}\) is strongly heated, you obtain another white solid, \(\mathbf{B},\) and a gas. An experiment is carried out on the gas, showing that it exerts a pressure of \(209 \mathrm{mm}\) Hg in a \(450-\mathrm{mL}\) flask at \(25^{\circ} \mathrm{C} .\) Bubbling the gas into a solution of \(\mathrm{Ca}(\mathrm{OH})_{2}\) gives another white solid, \(\mathrm{C}\). If the white solid B is added to water, the resulting solution turns red litmus paper blue. Addition of aqueous HCl to the solution of \(\mathbf{B}\) and evaporation of the resulting solution to dryness yield 1.055 g of a white solid D. When \(\mathbf{D}\) is placed in a Bunsen burner flame, it colors the flame green. Finally, if the aqueous solution of \(\mathbf{B}\) is treated with sulfuric acid, a white precipitate, \(\mathbf{E},\) forms. Identify the reaction scheme. (IMAGE CAN'T COPY)

A In \(1937,\) R. Schwartz and M. Schmiesser prepared a yellow-orange bromine oxide \(\left(\mathrm{BrO}_{2}\right)\) by treating \(\mathrm{Br}_{2}\) with ozone in a fluorocarbon solvent. Many years later, J. Pascal found that, on heating, this oxide decomposed to two other oxides, a less volatile golden yellow oxide (A) and a more volatile deep brown oxide (B). Oxide B was later identified as \(\mathrm{Br}_{2} \mathrm{O}\). To determine the formula for oxide \(\mathbf{A},\) a sample was treated with sodium iodide. The reaction liberated iodine, which was titrated to an equivalence point with \(17.7 \mathrm{mL}\) of \(0.065 \mathrm{M}\) sodium thiosulfate. \(\mathrm{I}_{2}(\mathrm{aq})+2 \mathrm{S}_{2} \mathrm{O}_{3}^{2-}(\mathrm{aq}) \rightarrow 2 \mathrm{I}^{-}(\mathrm{aq})+\mathrm{S}_{4} \mathrm{O}_{6}^{2-}(\mathrm{aq})\) Compound A was also treated with AgNO \(_{3}\), and \(14.4 \mathrm{mL}\) of \(0.020 \mathrm{M} \mathrm{AgNO}_{3}\) was required to completely precipitate the bromine from the sample. (a) What is the formula of the unknown bromine oxide \(\mathbf{A} ?\) (b) Draw Lewis structures for \(\mathrm{A}\) and \(\mathrm{Br}_{2} \mathrm{O}\). Speculate on their molecular geometry.

The density of lead is \(11.350 \mathrm{g} / \mathrm{cm}^{3},\) and the metal crystallizes in a face-centered cubic unit cell. Estimate the radius of a lead atom.