Chapter Questions
Define mineral, ore, and metallurgy.
List three metals that are usually found in an uncombined state in nature and three metals that are always found in a combined state in nature.
Write chemical formulas for the following minerals:(a) calcite, (b) dolomite, (c) fluorite, (d) halite, (e) corundum, (f) magnetite, (g) beryl, (h) galena, (i) epsomite, (j) anhydrite.
Name the following minerals: $(a) M g C O_{3}$,$(b) N a_{3} A I F_{6}$$(c) \mathrm{Al}_{2} \mathrm{O}_{3},$ $(d) \mathrm{Ag}_{2} \mathrm{S},$ $(e) \mathrm{HgS},$ $(f) \mathrm{ZnS},$ $ (g) \mathrm{SrSO}_{4}$ $(h) \mathrm{PbCO}_{3},$ $(i) \mathrm{MnO}_{2},$$(\mathrm{j}) \mathrm{Ti} \mathrm{O}_{2}$
Describe the main steps involved in the preparation of an ore.
What does roasting mean in metallurgy? Why is roasting a major source of air pollution and acid rain?
Describe with examples the chemical and electrolytic reduction processes used in the production of metals.
Describe the main steps used to purify metals.
Describe the extraction of iron in a blast furnace.
Briefly discuss the steelmaking process.
In the Mond process for the purification of nickel, CO is passed over metallic nickel to give $\mathrm{Ni}(\mathrm{CO})_{4}$$$\mathrm{Ni}(s)+4 \mathrm{CO}(g) \rightleftharpoons \mathrm{Ni}(\mathrm{CO})_{4}(g)$$Given that the standard free energies of formation of $\mathrm{CO}(g)$ and $\mathrm{Ni}(\mathrm{CO})_{4}(g)$ are $-137.3 \mathrm{kJ} / \mathrm{mol}$ and $-587.4 \mathrm{kJ} / \mathrm{mol},$ respectively, calculate the equilibrium constant of the reaction at $80^{\circ} \mathrm{C}$. (Assume $\Delta G_{\mathrm{f}}^{\circ}$ to be independent of temperature.)
Copper is purified by electrolysis (see Figure 21.6 ).A $5.00-\mathrm{kg}$ anode is used in a cell where the current is 37.8 A. How long (in hours) must the current run to dissolve this anode and electroplate it onto the cathode?
Consider the electrolytic procedure for purifying copper described in Figure $21.6 .$ Suppose that a sample of copper contains the following impurities:$Fe, A g, Z n, A u, C o, P t,$ and $P b .$ Which of the metals will be oxidized and dissolved in solution and which will be unaffected and simply form the sludge that accumulates at the bottom of the cell?
How would you obtain zinc from sphalerite (ZnS)?
Starting with rutile (TiO_), explain how you would obtain pure titanium metal. (Hint: First convert $\mathrm{Ti} \mathrm{O}_{2}$ to TiCl_t. Next, reduce TiCl_ with Mg. Look up physical properties of $\mathrm{TiCl}_{4}, \mathrm{Mg},$ and $\mathrm{MgCl}_{2}$ in a chemistry handbook.)
A certain mine produces $2.0 \times 10^{8} \mathrm{kg}$ of copper from chalcopyrite (CuFeS_) each year. The ore contains only 0.80 percent Cu by mass. (a) If the density of the ore is $2.8 \mathrm{g} / \mathrm{cm}^{3}$, calculate the volume (in $\mathrm{cm}^{3}$ ) of ore removed each year. (b) Calculate the mass (in $\mathrm{kg}$ ) of $\mathrm{SO}_{2}$ produced by roasting (assume chalcopyrite to be the only source of sulfur).
Which of the following compounds would requi electrolysis to yield the free metals? $\mathrm{Ag}_{2} \mathrm{S}, \mathrm{CaC} \mathrm{NaCl}, \mathrm{Fe}_{2} \mathrm{O}_{3}, \mathrm{Al}_{2} \mathrm{O}_{3}, \mathrm{TiCl}$
Although iron is only about two-thirds as abundant as aluminum in Earth's crust, mass for mass it costs only about one-quarter as much to produce. Why?
Define the following terms: conductor, insulator, semiconducting elements, donor impurities, acceptor impurities, $n$ -type semiconductors, $p$ -type semiconductors.
Briefly discuss the nature of bonding in metals, insulators, and semiconducting elements.
Describe the general characteristics of $n$ -type and $p$ -type semiconductors.
State whether silicon would form $n$ -type or $p$ -type semiconductors with the following elements: Ga, $\mathrm{Sb}, \mathrm{Al}, \mathrm{As}$
How is sodium prepared commercially?
Why is potassium usually not prepared electrolytically from one of its salts?
Describe the uses of the following compounds:$\mathrm{NaCl}, \mathrm{Na}_{2} \mathrm{CO}_{3}, \mathrm{NaOH}, \mathrm{KOH}, \mathrm{KO}_{2}$
Under what conditions do sodium and potassium form $\mathrm{Na}^{-}$ and $\mathrm{K}^{-}$ ions?
Complete and balance the following equations:(a) $\mathrm{K}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow$(b) $\operatorname{NaH}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow$(c) $\mathrm{Na}(s)+\mathrm{O}_{2}(g) \longrightarrow$(d) $\mathrm{K}(s)+\mathrm{O}_{2}(g) \longrightarrow$
Write a balanced equation for each of the following reactions: (a) sodium reacts with water; (b) an aqueous solution of $\mathrm{NaOH}$ reacts with $\mathrm{CO}_{2} ;$ (c) solid $\mathrm{Na}_{2} \mathrm{CO}_{3}$ reacts with a HCl solution; (d) solid $\mathrm{NaHCO}_{3}$ reacts with a HCl solution; (e) solid $\mathrm{NaHCO}_{3}$ is heated; (f) solid $\mathrm{Na}_{2} \mathrm{CO}_{3}$ is heated.
Sodium hydride (NaH) can be used as a drying agent for many organic solvents. Explain how it works.
Calculate the volume of $\mathrm{CO}_{2}$ at $10.0^{\circ} \mathrm{C}$ and $746 \mathrm{mmHg}$ pressure obtained by treating $25.0 \mathrm{g}$ of $\mathrm{Na}_{2} \mathrm{CO}_{3}$ with an excess of hydrochloric acid.
List the common ores of magnesium and calcium.
How are the metals magnesium and calcium obtained commercially?
From the thermodynamic data in Appendix $3,$ calculate the $\Delta H^{\circ}$ values for the following decompositions:(a) $\operatorname{MgCO}_{3}(s) \longrightarrow \operatorname{MgO}(s)+\mathrm{CO}_{2}(g)$(b) $\mathrm{CaCO}_{3}(s) \longrightarrow \mathrm{CaO}(s)+\mathrm{CO}_{2}(g)$Which of the two compounds is more easily decomposed by heat?
Starting with magnesium and concentrated nitric acid, describe how you would prepare magnesium oxide. [Hint: First convert Mg to Mg(NO_)_2. Next, $\left.\mathrm{MgO} \text { can be obtained by heating } \mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2} .\right]$
Describe two ways of preparing magnesium chloride.
The second ionization energy of magnesium is only about twice as great as the first, but the third ionization energy is 10 times as great. Why does it take so much more energy to remove the third electron??
List the sulfates of the Group 2 A metals in order of increasing solubility in water. Explain the trend. (Hint: You need to consult a chemistry handbook.)
Helium contains the same number of electrons in its outer shell as do the alkaline earth metals. Explain why helium is inert whereas the Group 2 A metals are not.
When exposed to air, calcium first forms calcium oxide, which is then converted to calcium hydroxide, and finally to calcium carbonate. Write a balanced equation for each step.
Write chemical formulas for (a) quicklime, (b) slaked lime, (c) limewater.
Describe the Hall process for preparing aluminum.
What action renders aluminum inert?
Before Hall invented his electrolytic process, aluminum was produced by the reduction of its chloride with an active metal. Which metals would you use for the production of aluminum in that way?
With the Hall process, how many hours will it take to deposit 664 g of Al at a current of $32.6 \mathrm{A} ?$
Aluminum forms the complex ions $\mathrm{AlCl}_{4}^{-}$ and $\mathrm{AlF}_{6}^{3-}$ Describe the shapes of these ions. $\mathrm{AlCl}_{6}^{3-}$ does not form. Why? (Hint: Consider the relative sizes of $\mathrm{Al}^{3+}$ $F^{2}$ and $C I^{2}$ ions.
The overall reaction for the electrolytic production of aluminum by means of the Hall process may be represented as $$\mathrm{Al}_{2} \mathrm{O}_{3}(s)+3 \mathrm{C}(s) \longrightarrow 2 \mathrm{Al}(l)+3 \mathrm{CO}(g)$$At $1000^{\circ} \mathrm{C},$ the standard free-energy change for this process is $594 \mathrm{kJ} / \mathrm{mol} .$ (a) Calculate the minimum voltage required to produce 1 mole of aluminum at this temperature. (b) If the actual voltage applied is exactly three times the ideal value, calculate the energy required to produce $1.00 \mathrm{kg}$ of the metal.
In basic solution, aluminum metal is a strong reducing agent and is oxidized to $\mathrm{AlO}_{2}^{-}$. Give balanced equations for the reaction of $\mathrm{Al}$ in basic solution with the following: (a) $\mathrm{NaNO}_{3},$ to give ammonia; (b) water, to give hydrogen; (c) $\mathrm{Na}_{2} \mathrm{SnO}_{3}$ to give metallic tin.
Write a balanced equation for the thermal decomposition of aluminum nitrate to form aluminum oxide, nitrogen dioxide, and oxygen gas.
Describe some of the properties of aluminum that make it one of the most versatile metals known.
The pressure of gaseous $\mathrm{Al}_{2} \mathrm{Cl}_{6}$ increases more rapidly with temperature than predicted by the ideal gas equation even though $\mathrm{Al}_{2} \mathrm{Cl}_{6}$ behaves like an ideal gas. Explain.
Starting with aluminum, describe with balanced equations how you would prepare $(a) \mathrm{Al}_{2} \mathrm{Cl}_{6}, (b) \mathrm{Al}_{2} \mathrm{O}_{3} (c) \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3},(\mathrm{d}) \mathrm{NH}_{4} \mathrm{Al}\left(\mathrm{SO}_{4}\right)_{2} \cdot 12 \mathrm{H}_{2} \mathrm{O}$
Explain the change in bonding when $\mathrm{Al}_{2} \mathrm{Cl}_{6}$ dissociates to form $\mathrm{AlCl}_{3}$ in the gas phase.
In steelmaking, nonmetallic impurities such as $\mathrm{P}, \mathrm{S}$ and Si are removed as the corresponding oxides. The inside of the furnace is usually lined with $\mathrm{CaCO}_{3}$ and $\mathrm{MgCO}_{3},$ which decompose at high temperatures to yield $\mathrm{CaO}$ and $\mathrm{MgO}$. How do $\mathrm{CaO}$ and $\mathrm{MgO}$ help in the removal of the nonmetallic oxides?
When $1.164 \mathrm{g}$ of a certain metal sulfide was roasted in air, $0.972 \mathrm{g}$ of the metal oxide was formed. If the oxidation number of the metal is $+2,$ calculate the molar mass of the metal.
An early view of metallic bonding assumed that bonding in metals consisted of localized, shared electron-pair bonds between metal atoms. What evidence would help you to argue against this viewpoint?
Referring to Figure $21.6,$ would you expect $\mathrm{H}_{2} \mathrm{O}$ and $\mathrm{H}^{+}$ to be reduced at the cathode and $\mathrm{H}_{2} \mathrm{O}$ oxidized at the anode?
A 0.450 -g sample of steel contains manganese as an impurity. The sample is dissolved in acidic solution and the manganese is oxidized to the permanganate ion $\mathrm{MnO}_{4}^{-}$. The $\mathrm{MnO}_{4}^{-}$ ion is reduced to $\mathrm{Mn}^{2+}$ by reacting with $50.0 \mathrm{mL}$ of $0.0800 \mathrm{M}$ $\mathrm{FeSO}_{4}$ solution. The excess $\mathrm{Fe}^{2+}$ ions are then oxidized to $\mathrm{Fe}^{3+}$ by $22.4 \mathrm{mL}$ of $0.0100 \mathrm{M} \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ Calculate the percent by mass of manganese in the sample.
Given that $\Delta G_{f}^{\circ}\left(\mathrm{Fe}_{2} \mathrm{O}_{3}\right)=-741.0 \mathrm{kJ} / \mathrm{mol}$ and that $\Delta G_{\mathrm{f}}^{\circ}\left(\mathrm{Al}_{2} \mathrm{O}_{3}\right)=-1576.4 \mathrm{kJ} / \mathrm{mol},$ calculate $\Delta G^{\circ}$ forthe following reactions at $25^{\circ} \mathrm{C}:$(a) $2 \mathrm{Fe}_{2} \mathrm{O}_{3}(s) \longrightarrow 4 \mathrm{Fe}(s)+3 \mathrm{O}_{2}(g)$(b) $2 \mathrm{Al}_{2} \mathrm{O}_{3}(s) \longrightarrow 4 \mathrm{Al}(s)+3 \mathrm{O}_{2}(g)$
Use compounds of aluminum as an example to explain what is meant by amphoterism.
When an inert atmosphere is needed for a metallurgical process, nitrogen is frequently used. However, in the reduction of $\mathrm{TiCl}_{4}$ by magnesium, helium is used. Explain why nitrogen is not suitable for this process.
It has been shown that $\mathrm{Na}_{2}$ species form in the vapor phase. Describe the formation of the "disodium molecule" in terms of a molecular orbital energylevel diagram. Would you expect the alkaline earth metals to exhibit a similar property?
Explain each of the following statements: (a) An aqueous solution of $\mathrm{AlCl}_{3}$ is acidic. (b) $\mathrm{Al}(\mathrm{OH})_{3}$ is soluble in NaOH solutions but not in $\mathrm{NH}_{3}$ solution.
Write balanced equations for the following reactions: (a) the heating of aluminum carbonate; (b) the reaction between $\mathrm{AlCl}_{3}$ and $\mathrm{K} ;$ (c) the reaction between solutions of $\mathrm{Na}_{2} \mathrm{CO}_{3}$ and $\mathrm{Ca}(\mathrm{OH})_{2}$
Write a balanced equation for the reaction between calcium oxide and dilute HCl solution.
What is wrong with the following procedure for obtaining magnesium?$$\begin{array}{r}\mathrm{MgCO}_{3} \longrightarrow \mathrm{MgO}(s)+\mathrm{CO}_{2}(g) \\\mathrm{MgO}(s)+\mathrm{CO}(g) \longrightarrow \mathrm{Mg}(s)+\mathrm{CO}_{2}(g)\end{array}$$
Explain why most metals have a flickering appearance.
Predict the chemical properties of francium, the last member of Group 1A.
Describe a medicinal or health-related application for each of the following compounds: $\mathrm{NaF}, \mathrm{Li}_{2} \mathrm{CO}_{3}$ $\mathrm{Mg}(\mathrm{OH})_{2}, \mathrm{CaCO}_{3}, \mathrm{BaSO}_{4}, \mathrm{Al}(\mathrm{OH})_{2} \mathrm{NaCO}_{3}$ would need to do a Web search for some of these compounds.)
The following are two reaction schemes involving magnesium. Scheme I: When magnesium burns in oxygen, a white solid (A) is formed. A dissolves in 1 $M$ HCl to give a colorless solution (B). Upon addition of $\mathrm{Na}_{2} \mathrm{CO}_{3}$ to $\mathrm{B},$ a white precipitate is formed (C). On heating, C decomposes to D and a colorless gas is generated (E). When $\mathrm{E}$ is passed through limewater [an aqueous suspension of $\left.\mathrm{Ca}(\mathrm{OH})_{2}\right],$ a white precipitate appears (F). Scheme $I I$ Magnesium reacts with 1 $M \mathrm{H}_{2} \mathrm{SO}_{4}$ to produce a colorless solution (G). Treating G with an excess of $\mathrm{NaOH}$ produces a white precipitate (H). H dissolves in $1 M \mathrm{HNO}_{3}$ to form a colorless solution. When the solution is slowly evaporated, a white solid (I) appears. On heating I, a brown gas is given off. Identify A-I and write equations representing the reactions involved.
Lithium and magnesium exhibit a diagonal relationship in some chemical properties. How does lithium resemble magnesium in its reaction with oxygen and nitrogen? Consult a handbook of chemistry and compare the solubilities of carbonates, fluorides, and phosphates of these metals.
To prevent the formation of oxides, peroxides, and superoxides, alkali metals are sometimes stored in an inert atmosphere. Which of the following gases should not be used for lithium? Why? $Ne, Ar, \mathrm{N}_{2}, \mathrm{Kr}$
Which of the following metals is not found in the free state in nature: $\mathrm{Ag}, \mathrm{Cu}, \mathrm{Zn}, \mathrm{Au}, \mathrm{Pt} ?$
After heating, a metal surface (such as that of a cooking pan or skillet) develops a color pattern like an oil slick on water. Explain.
Chemical tests of four metals $A, B, C,$ and $D$ show the following results.(a) Only B and C react with $0.5 M$ HCl to give $\mathrm{H}_{2}$ gas.(b) When $\mathrm{B}$ is added to a solution containing the ions of the other metals, metallic A, C, and D are formed.(c) A reacts with $6 M \mathrm{HNO}_{3}$ but $\mathrm{D}$ does not. Arrange the metals in the increasing order as reducing agents. Suggest four metals that fit these descriptions.
The electrical conductance of copper metal decreases with temperature, but that of a CuSO $_{4}$ solution increases with temperature. Explain.
As stated in the chapter, potassium superoxide $\left(\mathrm{KO}_{2}\right)$ is a useful source of oxygen employed in breathing equipment. Calculate the pressure at which oxygen gas stored at $20^{\circ} \mathrm{C}$ would have the same density as the oxygen gas provided by $\mathrm{KO}_{2}$ The density of $\mathrm{KO}_{2}$ at $20^{\circ} \mathrm{C}$ is $2.15 \mathrm{g} / \mathrm{cm}^{3}$
A sample of $10.00 \mathrm{g}$ of sodium reacts with oxygen to form $13.83 \mathrm{g}$ of sodium oxide $\left(\mathrm{Na}_{2} \mathrm{O}\right)$ and sodium peroxide $\left(\mathrm{Na}_{2} \mathrm{O}_{2}\right) .$ Calculate the percent composition of the mixture.