Chemistry

Raymond Chang, Jason Overby

Chapter 21 Metallurgy and the Chemistry of Metals - all with Video Answers

Educators

Chapter Questions

01:20

Problem 1

Define mineral, ore, and metallurgy.

Elham Kordzadeh

Numerade Educator

00:39

Problem 2

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.

Elham Kordzadeh

Numerade Educator

02:51

Problem 3

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.

Elham Kordzadeh

Numerade Educator

02:07

Name the following minerals: (a) $\mathrm{MgCO}_3$, (b) $\mathrm{Na}_3 \mathrm{AlF}_6$, (c) $\mathrm{Al}_2 \mathrm{O}_3$, (d) $\mathrm{Ag}_2 \mathrm{~S}$, (e) HgS, (f) ZnS , (g) $\mathrm{SrSO}_4$, (h) $\mathrm{PbCO}_3$, (i) $\mathrm{MnO}_2$, (j) $\mathrm{TiO}_2$.

Marissa Turner

Numerade Educator

05:02

Problem 5

Describe the main steps involved in the preparation of an ore.

Elham Kordzadeh

Numerade Educator

01:41

Problem 6

What does roasting mean in metallurgy? Why is roasting a major source of air pollution and acid rain?

Elham Kordzadeh

Numerade Educator

04:37

Problem 7

Describe with examples the chemical and electrolytic reduction processes used in the production of metals.

Elham Kordzadeh

Numerade Educator

05:04

Problem 8

Describe the main steps used to purify metals.

Elham Kordzadeh

Numerade Educator

05:00

Problem 9

Describe the extraction of iron in a blast furnace.

Elham Kordzadeh

Numerade Educator

01:22

Problem 10

Briefly discuss the steelmaking process.

Harshit Mawandia

Numerade Educator

03:53

Problem 11

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 $\mathrm{CO}(\mathrm{g})$ and $\mathrm{Ni}(\mathrm{CO})_4(\mathrm{~g})$ 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 $\Delta G_Y$ to be independent of temperature.)

Elham Kordzadeh

Numerade Educator

04:05

Problem 12

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?

Elham Kordzadeh

Numerade Educator

00:50

Problem 13

Consider the electrolytic procedure for purifying copper described in Figure 21.6. Suppose that a sample of copper contains the following impurities: $\mathrm{Fe}, \mathrm{Ag}, \mathrm{Zn}, \mathrm{Au}, \mathrm{Co}, \mathrm{Pt}$, and Pb . 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?

Marissa Turner

Numerade Educator

03:31

Problem 14

How would you obtain zinc from sphalerite ( ZnS )?

Elham Kordzadeh

Numerade Educator

02:40

Problem 15

Starting with rutile ( $\mathrm{TiO}_2$ ), explain how you would obtain pure titanium metal. (Hint: First convert $\mathrm{TiO}_2$ to $\mathrm{TiCl}_4$. Next, reduce $\mathrm{TiCl}_4$ with Mg . Look up physical properties of $\mathrm{TiCl}_4, \mathrm{Mg}$, and $\mathrm{MgCl}_2$ in a chemistry handbook.)

Marissa Turner

Numerade Educator

01:01

Problem 16

A certain mine produces $2.0 \times 10^8 \mathrm{~kg}$ of copper from chalcopyrite ( $\mathrm{CuFeS}_2$ ) 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 kg ) of $\mathrm{SO}_2$ produced by roasting (assume chalcopyrite to be the only source of sulfur).

Manik Pulyani

Numerade Educator

00:43

Problem 17

Which of the following compounds would require electrolysis to yield the free metals: $\mathrm{Ag}_2 \mathrm{~S}, \mathrm{CaCl}_2, \mathrm{NaCl}, \mathrm{Fe}_2 \mathrm{O}_3, \mathrm{Al}_2 \mathrm{O}_3, \mathrm{TiCl}_4$ ?

Marissa Turner

Numerade Educator

00:32

Problem 18

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?
21.3 Band Theory of Electrical Conductivity

Elham Kordzadeh

Numerade Educator

02:14

Problem 19

Define the following terms: conductor, insulator, semiconducting elements, donor impurities, acceptor impurities, n-type semiconductors, and p-type semiconductors.

Marissa Turner

Numerade Educator

02:35

Problem 20

Briefly discuss the nature of bonding in metals, insulators, and semiconducting elements.

Elham Kordzadeh

Numerade Educator

00:52

Problem 21

Describe the general characteristics of $n$-type and $p$-type semiconductors.

Elham Kordzadeh

Numerade Educator

01:08

Problem 22

State whether silicon would form $n$-type or $p$-type semiconductors with the following elements: $\mathrm{Ga}, \mathrm{Sb}, \mathrm{Al}, \mathrm{As}$.

Marissa Turner

Numerade Educator

01:39

Problem 23

How is sodium prepared commercially?

Elham Kordzadeh

Numerade Educator

00:12

Problem 24

Why is potassium usually not prepared electrolytically from one of its salts?

Elham Kordzadeh

Numerade Educator

01:48

Problem 25

Describe the uses of the following compounds: $\mathrm{NaCl}, \mathrm{Na}_2 \mathrm{CO}_3, \mathrm{NaOH}, \mathrm{KOH}, \mathrm{KO}_2$.

Elham Kordzadeh

Numerade Educator

01:56

Problem 26

Under what conditions do sodium and potassium form $\mathrm{Na}^{-}$and $\mathrm{K}^{-}$ions?

Susan Hallstrom

Numerade Educator

02:09

Problem 27

Complete and balance the following equations:
(a) $\mathrm{K}(s)+\mathrm{H}_2 \mathrm{O}(l) \rightarrow$
(b) $\mathrm{NaH}(s)+\mathrm{H}_2 \mathrm{O}(l) \rightarrow$
(c) $\mathrm{Na}(s)+\mathrm{O}_2(g) \rightarrow$
(d) $\mathrm{K}(s)+\mathrm{O}_2(g) \rightarrow$

Marissa Turner

Numerade Educator

06:36

Problem 28

Write a balanced equation for each of the following reactions: (a) Sodium reacts with water; (b) an aqueous solution of 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.

Elham Kordzadeh

Numerade Educator

01:26

Problem 29

Sodium hydride $(\mathrm{NaH})$ can be used as a drying agent for many organic solvents. Explain how it works.

Elham Kordzadeh

Numerade Educator

03:23

Problem 30

Calculate the volume of $\mathrm{CO}_2$ at $10.0^{\circ} \mathrm{C}$ and 746 mmHg pressure obtained by treating 25.0 g of $\mathrm{Na}_2 \mathrm{CO}_3$ with an excess of hydrochloric acid.

Elham Kordzadeh

Numerade Educator

03:41

Problem 31

List the common ores of magnesium and calcium.

Elham Kordzadeh

Numerade Educator

02:37

Problem 32

How are the metals magnesium and calcium obtained commercially?

Elham Kordzadeh

Numerade Educator

02:59

Problem 33

From the thermodynamic data in Appendix 2, calculate the $\Delta H^{\circ}$ values for the following decompositions:
(a) $\mathrm{MgCO}_3(s) \rightarrow \mathrm{MgO}(s)+\mathrm{CO}_2(g)$
(b) $\mathrm{CaCO}_3(s) \rightarrow \mathrm{CaO}(s)+\mathrm{CO}_2(g)$

Which of the two compounds is more easily decomposed by heat?

Jorge Villanueva

Numerade Educator

02:37

Problem 34

Starting with magnesium and concentrated nitric acid, describe how you would prepare magnesium oxide. [Hint: First convert Mg to $\mathrm{Mg}\left(\mathrm{NO}_3\right)_2$. Next, MgO can be obtained by heating $\mathrm{Mg}\left(\mathrm{NO}_3\right)_2$.]

Marissa Turner

Numerade Educator

02:46

Problem 35

Describe two ways of preparing magnesium chloride.

Elham Kordzadeh

Numerade Educator

01:25

Problem 36

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?

Marissa Turner

Numerade Educator

01:12

Problem 37

List the sulfates of the Group 2 metals in order of increasing solubility in water. Explain the trend. (Hint: You need to consult a chemistry handbook.)

Elham Kordzadeh

Numerade Educator

01:04

Problem 38

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 metals are not.

Marissa Turner

Numerade Educator

01:41

Problem 39

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.

Elham Kordzadeh

Numerade Educator

00:47

Problem 40

Write chemical formulas for (a) quicklime, (b) slaked lime, (c) limewater.

Elham Kordzadeh

Numerade Educator

02:18

Problem 41

Describe the Hall process for preparing aluminum.

Elham Kordzadeh

Numerade Educator

00:42

Problem 42

What action renders aluminum inert?

Elham Kordzadeh

Numerade Educator

00:36

Problem 43

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?

Elham Kordzadeh

Numerade Educator

02:39

Problem 44

With the Hall process, how many hours will it take to deposit 664 g of Al at a current of 32.6 A ?

Elham Kordzadeh

Numerade Educator

03:06

Problem 45

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 $\mathrm{Al}^{3+}, \mathrm{F}^{-}$, and $\mathrm{Cl}^{-}$ions.)

Marissa Turner

Numerade Educator

04:24

Problem 46

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 Gibbs-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 kg of the metal.

Elham Kordzadeh

Numerade Educator

04:56

Problem 47

In basic solution, aluminum metal is a strong reducing agent and is oxidized to $\mathrm{AlO}_2^{-}$. Give balanced equations for the reaction of 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.

Elham Kordzadeh

Numerade Educator

01:07

Problem 48

Write a balanced equation for the thermal decomposition of aluminum nitrate to form aluminum oxide, nitrogen dioxide, and oxygen gas.

Elham Kordzadeh

Numerade Educator

00:28

Problem 49

Describe some of the properties of aluminum that make it one of the most versatile metals known.

Elham Kordzadeh

Numerade Educator

01:15

Problem 50

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.

Elham Kordzadeh

Numerade Educator

05:32

Problem 51

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) $\mathrm{Al}_2\left(\mathrm{SO}_4\right)_3$, (d) $\mathrm{NH}_4 \mathrm{Al}\left(\mathrm{SO}_4\right)_2 \cdot 12 \mathrm{H}_2 \mathrm{O}$.

Marissa Turner

Numerade Educator

View

Problem 52

Explain the change in bonding when $\mathrm{Al}_2 \mathrm{Cl}_6$ dissociates to form $\mathrm{AlCl}_3$ in the gas phase.

Elham Kordzadeh

Numerade Educator

02:10

Problem 53

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 CaO and MgO . How do CaO and MgO help in the removal of the nonmetallic oxides?

Elham Kordzadeh

Numerade Educator

01:46

Problem 54

When 1.164 g of a certain metal sulfide was roasted in air, 0.972 g of the metal oxide was formed. If the oxidation number of the metal is +2 , calculate the molar mass of the metal.

Elham Kordzadeh

Numerade Educator

00:22

Problem 55

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?

Elham Kordzadeh

Numerade Educator

00:16

Problem 56

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?

Elham Kordzadeh

Numerade Educator

02:33

Problem 57

A $0.450-\mathrm{g}$ 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 mL of $0.0800 M \mathrm{FeSO}_4$ solution. The excess $\mathrm{Fe}^{2+}$ ions are then oxidized to $\mathrm{Fe}^{3+}$ by 22.4 mL of $0.0100 M \mathrm{~K}_2 \mathrm{Cr}_2 \mathrm{O}_7$. Calculate the percent by mass of manganese in the sample.

Manik Pulyani

Numerade Educator

03:08

Problem 58

Given that $\Delta G_{\mathrm{r}}^{\mathrm{r}}\left(\mathrm{Fe}_2 \mathrm{O}_3\right)=-741.0 \mathrm{~kJ} / \mathrm{mol}$ and that $\Delta G_{\mathrm{i}}^{\mathrm{z}}\left(\mathrm{Al}_2 \mathrm{O}_3\right)=-1576.4 \mathrm{~kJ} / \mathrm{mol}$, calculate $\Delta G^{\circ}$ for the 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) $2 \mathrm{Al}_2 \mathrm{O}_3(s) \longrightarrow 4 \mathrm{Al}(s)+3 \mathrm{O}_2(g)$

Elham Kordzadeh

Numerade Educator

01:30

Problem 59

Use compounds of aluminum as an example to explain what is meant by amphoterism.

Elham Kordzadeh

Numerade Educator

00:26

Problem 60

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.

Elham Kordzadeh

Numerade Educator

02:17

Problem 61

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 energy-level diagram. Would you expect the alkaline earth metals to exhibit a similar property?

Marissa Turner

Numerade Educator

02:10

Problem 62

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.

Elham Kordzadeh

Numerade Educator

03:40

Problem 63

Write balanced equations for the following reactions: (a) the heating of aluminum carbonate; (b) the reaction between $\mathrm{AlCl}_3$ and K ; (c) the reaction between solutions of $\mathrm{Na}_2 \mathrm{CO}_3$ and $\mathrm{Ca}(\mathrm{OH})_2$.

Marissa Turner

Numerade Educator

00:53

Problem 64

Write a balanced equation for the reaction between calcium oxide and dilute HCl solution.

Elham Kordzadeh

Numerade Educator

00:42

Problem 65

What is wrong with the following procedure for obtaining magnesium?
$$
\begin{gathered}
\mathrm{MgCO}_3 \longrightarrow \mathrm{MgO}(s)+\mathrm{CO}_2(g) \\
\mathrm{MgO}(s)+\mathrm{CO}(g) \rightarrow \mathrm{Mg}(s)+\mathrm{CO}_2(g)
\end{gathered}
$$

Elham Kordzadeh

Numerade Educator

00:20

Problem 66

Explain why most metals have a flickering appearance.

Elham Kordzadeh

Numerade Educator

00:19

Problem 67

Predict the chemical properties of francium, the last member of Group 1.

Elham Kordzadeh

Numerade Educator

02:48

Problem 68

Describe a medicinal or health-related application for each of the following compounds: $\mathrm{NaF}, \mathrm{Li}_2 \mathrm{CO}_3, \mathrm{Mg}(\mathrm{OH})_2, \mathrm{CaCO}_3, \mathrm{BaSO}_4, \mathrm{Al}(\mathrm{OH})_2 \mathrm{NaCO}_3$. (You will need to do a Web search for some of these compounds.)

Anand Jangid

Numerade Educator

07:09

Problem 69

The following are two reaction schemes involving magnesium. Scheme I: When magnesium burns in oxygen, a white solid (A) is formed. A dissolves in $1 M \mathrm{HCl}$ to give a colorless solution (B). Upon addition of $\mathrm{Na}_2 \mathrm{CO}_3$ to B , a white precipitate is formed (C). On heating, C decomposes to D and a colorless gas is generated (E). When E is passed through limewater [an aqueous suspension of $\mathrm{Ca}(\mathrm{OH})_2$ ], a white precipitate appears (F). Scheme II: Magnesium reacts with $1 M \mathrm{H}_2 \mathrm{SO}_4$ to produce a colorless solution (G). Treating G with an excess of NaOH produces a white precipitate $(\mathrm{H}) . \mathrm{H}$ 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.

Marissa Turner

Numerade Educator

00:50

Problem 70

Lithium and magnesium exhibit a diagonal relationship in some chemical properties. How does lithium resemble magnesium in its reaction with (i) oxygen and (ii) nitrogen? Consult a handbook of chemistry and compare the solubilities of (iii) carbonates, fluorides, and phosphates of these metals.

Elham Kordzadeh

Numerade Educator

01:05

Problem 71

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: $\mathrm{Ne}, \mathrm{Ar}, \mathrm{N}_2, \mathrm{Kr}$ ? Explain why.

Marissa Turner

Numerade Educator

00:45

Problem 72

Which of the following metals is not found in the free state in nature: $\mathrm{Ag}, \mathrm{Cu}, \mathrm{Zn}, \mathrm{Au}$, Pt?

Elham Kordzadeh

Numerade Educator

00:19

Problem 73

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.

Elham Kordzadeh

Numerade Educator

01:37

Problem 74

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 B is added to a solution containing the ions of the other metals, metallic $\mathrm{A}, \mathrm{C}$, and D are formed.
(c) A reacts with $6 M \mathrm{HNO}_3$ but D does not.

Arrange the metals in the increasing order as reducing agents. Suggest four metals that fit these descriptions.

Lottie Adams

Numerade Educator

02:24

Problem 75

The electrical conductance of copper metal decreases with temperature, but that of a $\mathrm{CuSO}_4$ solution increases with temperature. Explain.

Marissa Turner

Numerade Educator

03:20

Problem 76

As stated in the chapter, potassium superoxide ( $\mathrm{KO}_2$ ) 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 $2.15 \mathrm{~g} / \mathrm{cm}^3$.

Marissa Turner

Numerade Educator

06:37

Problem 77

A sample of 10.00 g of sodium reacts with oxygen to form 13.83 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.

Marissa Turner

Numerade Educator