Chapter 21

Which of the following formulas is incorrect? (a) \(\mathrm{CaH}_{2}\) (c) CaS (b) \(\mathrm{CaI}_{2}\) (d) \(\mathrm{Ca}_{2} \mathrm{O}_{3}\)

The reaction of elemental phosphorus and excess oxygen produces \(\mathrm{P}_{4} \mathrm{O}_{10} .\) Name the compound. (a) phosphorus oxide (b) phosphoric acid (c) phosphorus decaoxide (d) tetraphosphorus decaoxide

Like sulfur, selenium forms compounds in several different oxidation states. Which of the following is NOT likely to be an oxidation state of selenium in its compounds? (a) -2 (b) +3 \((c)+6\) \((d)+4\)

What is the highest oxidation state that antimony can have in its compounds? (a) 0 (b) +1 \((c)+3\) \((d)+5\)

Give examples of two basic oxides. Write equations illustrating the formation of each oxide from its component elements. Write another chemical equation that illustrates the basic character of each oxide.

Give examples of two acidic oxides. Write equations illustrating the formation of each oxide from its component elements. Write another chemical equation that illustrates the acidic character of each oxide.

Give symbols and names for four monatomic ions that have the same electron configuration as argon.

Select one of the alkali metals, and write a balanced chemical equation for its reaction with chlorine. Is the reaction likely to be exothermic or endothermic? Is the product ionic or molecular?

Select one of the alkaline earth metals and write a balanced chemical equation for its reaction with oxygen. Is the reaction likely to be exothermic or endothermic? Is the product ionic or molecular?

Would you expect to find calcium occurring naturally in the Earth's crust as a free element? Why or why not?

Which of the first 10 elements in the periodic table are found as free elements in the Earth's crust? Which elements in this group occur in the Earth's crust only as part of a chemical compound?

Place the following oxides in order of increasing basicity: \(\mathrm{CO}_{2}, \mathrm{SiO}_{2}, \mathrm{SnO}_{2}\)

Place the following oxides in order of increasing basicity: \(\mathrm{Na}_{2} \mathrm{O}, \mathrm{Al}_{2} \mathrm{O}_{3,} \mathrm{SiO}_{2}, \mathrm{SO}_{3}\)

Complete and balance the equations for the following reactions. [Assume an excess of oxygen for (d).] (a) \(\mathrm{Na}(\mathrm{s})+\mathrm{Br}_{2}(\ell) \rightarrow\) (c) \(\mathrm{Al}(\mathrm{s})+\mathrm{F}_{2}(\mathrm{g}) \rightarrow\) (b) \(\mathrm{Mg}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow\) (d) \(\mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow\)

Complete and balance the equations for the following reactions: (a) \(\mathrm{K}(\mathrm{s})+\mathrm{I}_{2}(\mathrm{g}) \rightarrow\) (c) \(\mathrm{Al}(\mathrm{s})+\mathrm{S}_{8}(\mathrm{s}) \rightarrow\) (b) \(\mathrm{Ba}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow\) (d) \(\mathrm{Si}(\mathrm{s})+\mathrm{Cl}_{2}(\mathrm{g}) \rightarrow\)

Which of the following elements does not react with hydrogen? (a) neon (c) potassium (b) nitrogen (d) fluorine

Which of the methods below is the most suitable for the preparation of large quantities of hydrogen (such as the amounts needed as a reagent for the synthesis of compounds such as ammonia)? (a) Electrolysis of water (b) The reaction of metal hydrides with water (c) The high-temperature reaction of methane and water (d) The reaction of zinc and hydrochloric acid

Write balanced chemical equations for the reaction of hydrogen gas with oxygen, chlorine, and nitrogen.

Write an equation for the reaction of potassium and hydrogen. Name the product. Is it ionic or covalent? Predict one physical property and one chemical property of this compound.

A method recently suggested for the preparation of hydrogen (and oxygen) from water proceeds as follows: (a) Sulfuric acid and hydrogen iodide are formed from sulfur dioxide, water, and iodine. (b) The sulfuric acid from the first step is decomposed by heat to water, sulfur dioxide, and oxygen. (c) The hydrogen iodide from the first step is decomposed with heat to hydrogen and iodine. Write a balanced equation for each of these steps, and show that their sum is the decomposition of water to form hydrogen and oxygen.

Compare the mass of \(\mathrm{H}_{2}\) expected from the reaction of steam \(\left(\mathrm{H}_{2} \mathrm{O}\right)\) per mole of methane, petroleum, and coal. (Assume complete reaction in each case. Use \(\mathrm{CH}_{2}\) and \(\mathrm{CH}\) as representative formulas for petroleum and coal, respectively.

Which of the following is not a property of sodium? (a) Reacts with \(\mathrm{Cl}_{2}\) to form \(\mathrm{NaCl}\) (b) Has a high melting point \(\left(>400^{\circ} \mathrm{C}\right)\) (c) Has a silvery color (d) Conducts an electric current

The compound \(\mathrm{Na}_{2} \mathrm{O}_{2}\) consists of (a) two \(\mathrm{Na}^{+}\) ions and two \(\mathrm{O}^{2-}\) ions (b) molecules of \(\mathrm{Na}_{2} \mathrm{O}_{2}\) (c) two \(\mathrm{Na}^{+}\) ions and one \(\mathrm{O}_{2}^{2-}\) ion (d) \(\mathrm{Na}^{2+}\) and \(\mathrm{O}^{2-}\) ions

Write equations for the reaction of sodium with each of the halogens. Predict at least two physical properties that are common to all of the alkali metal halides.

Write balanced equations for the reaction of lithium, sodium, and potassium with \(\mathrm{O}_{2} .\) Specify which metal forms an oxide, which forms a peroxide, and which forms a superoxide.

(a) Write equations for the half-reactions that occur at the cathode and the anode when an aqueous solution of KCl is electrolyzed. Which chemical species is oxidized, and which chemical species is reduced in this reaction? (b) Predict the products formed when an aqueous solution of CsI is electrolyzed.

Which of the following insoluble calcium compounds does not dissolve in hydrochloric acid? (a) limestone, \(\mathrm{CaCO}_{3}\) (b) slaked lime, \(\mathrm{Ca}(\mathrm{OH})_{2}\) (c) gypsum, \(\mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}\) (d) hydroxyapatite, \(\mathrm{Ca}_{5}(\mathrm{OH})\left(\mathrm{PO}_{4}\right)_{3}\)

Calcium minerals are the raw materials for a variety of large-scale industrial processes. Which of the following is not an industrial process? (a) Converting limestone, \(\mathrm{CaCO}_{3}\), to lime (b) Converting fluorite, \(\mathrm{CaF}_{2},\) to HF (c) Converting slaked lime, \(\mathrm{Ca}(\mathrm{OH})_{2}\), to lime (d) Converting apatite minerals to phosphate fertilizers

When magnesium burns in air, it forms both an oxide and a nitride. Write balanced equations for the formation of both compounds.

Calcium reacts with hydrogen gas at \(300-400^{\circ} \mathrm{C}\) to form a hydride. This compound reacts readily with water, so it is an excellent drying agent for organic solvents. (a) Write a balanced equation showing the formation of calcium hydride from Ca and \(\mathrm{H}_{2}\). (b) Write a balanced equation for the reaction of calcium hydride with water (Figure 21.7 ).

Name three uses of limestone. Write a balanced equation for the reaction of limestone with \(\mathrm{CO}_{2}\) in water.

Explain what is meant by "hard water." What causes hard water, and what problems are associated with it?

Calcium oxide, \(\mathrm{CaO}\), is used to remove \(\mathrm{SO}_{2}\) from ower plant exhaust. These two compounds react o give solid \(\mathrm{CaSO}_{3} .\) What mass of \(\mathrm{SO}_{2}\) can be emoved using \(1.2 \times 10^{3} \mathrm{kg}\) of \(\mathrm{CaO} ?\)

\(\mathrm{Ca}(\mathrm{OH})_{2}\) has a \(K_{\mathrm{sp}}\) of \(5.5 \times 10^{-5},\) whereas \(K_{\mathrm{sp}}\) for \(\mathrm{Mg}(\mathrm{OH})_{2}\) is \(5.6 \times 10^{-12} .\) Calculate the equilibrium constant for the reaction \(\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s})+\mathrm{Mg}^{2+}(\mathrm{aq}) \rightleftharpoons \mathrm{Ca}^{2+}(\mathrm{aq})+\mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s})\) Explain why this reaction can be used in the commercial isolation of magnesium from seawater.

In terms of abundance of the elements in the Earth's crust, aluminum ranks (a) first (c) third (b) second (d) fourth

The element below aluminum in Group \(3 \mathrm{A}\) is gallium, and there are numerous similarities in the chemistry of these two elements. For example, the hydroxides of both elements are amphoteric. A consequence of this is that both gallium hydroxide and aluminum hydroxide (a) are insoluble in water (b) dissolve only in acid (c) dissolve only in base (d) dissolve in acid and in base

Write balanced equations for the reactions of aluminum with HCl(aq), \(\mathrm{Cl}_{2},\) and \(\mathrm{O}_{2}\)

Aluminum dissolves readily in hot aqueous NaOH to give the aluminate ion, \(\left[\mathrm{Al}(\mathrm{OH})_{4}\right]^{-},\) and \(\mathrm{H}_{2} .\) Write a balanced equation for this reaction. If you begin with \(13.2 \mathrm{g}\) of \(\mathrm{Al}\), what volume (in liters) of \(\mathrm{H}_{2}\) gas is produced when the gas is measured at \(22.5^{\circ} \mathrm{C}\) and a pressure of \(735 \mathrm{mm} \mathrm{Hg} ?\)

Alumina, \(\mathrm{Al}_{2} \mathrm{O}_{3},\) is amphoteric. Among examples of its amphoteric character are the reactions that occur when \(\mathrm{Al}_{2} \mathrm{O}_{3}\) is heated strongly or "fused" with acidic oxides and basic oxides. (a) Write a balanced equation for the reaction of alumina with silica, an acidic oxide, to give aluminum metasilicate, \(\mathrm{Al}_{2}\left(\mathrm{SiO}_{3}\right)_{3}\) (b) Write a balanced equation for the reaction of alumina with the basic oxide CaO to give calcium aluminate, \(\operatorname{Ca}\left(\mathrm{AlO}_{2}\right)_{2}\)

"Aerated" concrete bricks are widely used building materials. They are obtained by mixing gasforming additives with a moist mixture of lime, cement, and possibly sand. Industrially, the following reaction is important:\(2 \mathrm{Al}(\mathrm{s})+3 \mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s})+6 \mathrm{H}_{2} \mathrm{O}(\ell) \rightarrow\) \(3 \mathrm{CaO} \cdot \mathrm{Al}_{2} \mathrm{O}_{3} \cdot 6 \mathrm{H}_{2} \mathrm{O}(\mathrm{s})+3 \mathrm{H}_{2}(\mathrm{g})\) Assume the mixture of reactants contains \(0.56 \mathrm{g}\) of Al (as well as excess calcium hydroxide and water) for each brick. What volume of hydrogen gas do you expect at \(26^{\circ} \mathrm{C}\) and a pressure of \(745 \mathrm{mm} \mathrm{Hg} ?\)

Elemental silicon is oxidized by \(\mathrm{O}_{2}\) to give unknown A. Compound \(A\) is dissolved in molten \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) giving \(\mathrm{B}\). When \(\mathrm{B}\) was treated with aqueous hydrochloric acid, \(\mathrm{C}\) is produced. Identify compound C. (a) \(\mathrm{SiH}_{4}\) (b) \(\mathrm{H}_{4} \mathrm{SiO}_{4}\) (c) \(\mathrm{SiO}_{2}\) (d) \(\operatorname{sicl}_{4}\)

Silicon and oxygen form a six-membered ring in the silicate anion \(\left[\mathrm{Si}_{3} \mathrm{O}_{9}\right]^{6-} .\) What is the oxidation state of silicon in this anion? (The rare blue mineral benitoite, the California state gemstone, has the formula \(\mathrm{BaTiSi}_{3} \mathrm{O}_{9 .}\) ) (a) 0 (b) +2 \((c)+4\) (d) -4

Silicate structures: Draw a structure, and give the charge for a cyclic silicate anion with the formula \(\left[\mathrm{Si}_{6} \mathrm{O}_{18}\right]^{\mathrm{n}-}\)

Construct Lewis structures for the several resonance forms of \(\mathrm{N}_{2}\) O. What is the predicted \(\mathrm{N}-\mathrm{N}\) bond order? (a) 1 (b) 2 (c) between 2 and 3 (d) 3

Which statement about ammonia is not correct? (a) Ammonia can be made by a direct reaction of the elements. (b) Aqueous solutions of ammonia are acidic. (c) Ammonia is a gas at room temperature and atmospheric pressure. (d) Ammonia is used as a reactant in the synthesis of nitric acid.

A major use of hydrazine, \(\mathrm{N}_{2} \mathrm{H}_{4},\) is in steam boilers in power plants. (a) The reaction of hydrazine with \(\mathrm{O}_{2}\) dissolved in water gives \(\mathrm{N}_{2}\) and water. Write a balanced equation for this reaction. (b) \(\mathrm{O}_{2}\) dissolves in water to the extent of \(0.0044 \mathrm{g}\) in \(100 .\) mL of water at \(20^{\circ}\) C. What mass of \(\mathrm{N}_{2} \mathrm{H}_{4}\) is needed to consume all of the dissolved \(\mathrm{O}_{2}\) in \(3.00 \times 10^{4} \mathrm{L}\) of water (enough to fill a small swimming pool)?

Unlike carbon, which can form extended chains of atoms, nitrogen can form chains of very limited length. Draw the Lewis electron dot structure of the azide ion, \(\mathrm{N}_{3}^{-} .\) Is the ion linear or bent?

Which of the following is not a common oxidation number for sulfur in its compounds? (a) -2 \((b)+6\) \((c)+3\) \((d)+4\)

Which statement about oxygen is not true? (a) Liquid oxygen is attracted to a magnet. (b) The allotropes of oxygen are \(\mathrm{O}_{2}\) and \(\mathrm{O}_{3}\) (c) Oxygen is the most abundant element in the Earth's crust. (d) All electrons in \(\mathrm{O}_{2}\) are paired.

In the "contact process" for making sulfuric acid, sulfur is first burned to \(\mathrm{SO}_{2}\). Environmental restrictions allow no more than \(0.30 \%\) of this \(\mathrm{SO}_{2}\) to be vented to the atmosphere. (a) If enough sulfur is burned in a plant to produce \(1.80 \times 10^{6} \mathrm{kg}\) of pure, anhydrous \(\mathrm{H}_{2} \mathrm{SO}_{4}\) per day, what is the maximum amount of \(\mathrm{SO}_{2}\) that is allowed to be exhausted to the atmosphere? (b) One way to prevent any \(\mathrm{SO}_{2}\) from reaching the atmosphere is to "scrub" the exhaust gases with slaked lime, \(\mathrm{Ca}(\mathrm{OH})_{2}\) \(\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s})+\mathrm{SO}_{2}(\mathrm{g}) \rightarrow \mathrm{CaSO}_{3}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\ell)\) $$ 2 \mathrm{CaSO}_{3}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow 2 \mathrm{CaSO}_{4}(\mathrm{s}) $$ What mass of \(\mathrm{Ca}(\mathrm{OH})_{2}\) (in kilograms) is needed to remove the \(\mathrm{SO}_{2}\) calculated in part (a)?