Chapter 22: The Elements in Nature and Industry
1. The Earth’s core consists mainly of
A) Ni. B) O. C) Al. D) Si. E) Fe.
2. The main effect of the biosphere on the chemistry of the earth’s crust has been to
A) create a reducing atmosphere.
B) create an oxidizing atmosphere.
C) increase the relative humidity.
D) decrease the relative humidity.
E) increase the level of atmospheric carbon dioxide.
3. The most abundant element in the Earth’s crust is
A) H. B) Fe. C) Al. D) Si. E) O.
4. Transition elements from the left side of the periodic table are generally found as
A) sulfides because they tend to give up bonding electrons and form crystals with
high lattice energies with sulfur.
B) sulfides because their electronegativities favor formation of covalent bonds with
the polarizable sulfide anion.
C) oxides because they tend to give up bonding electrons and form crystals with high
lattice energies with oxygen.
D) oxides because oxygen, with its high electronegativity, forms strong covalent
bonds with them.
E) the uncombined elements, because they are noble metals.
5. Transition elements from the right side of the periodic table are generally found as
A) sulfides because they tend to give up bonding electrons and form crystals with
high lattice energies with sulfur.
B) sulfides because their electronegativities favor formation of covalent bonds with
the polarizable sulfide anion.
C) oxides because they tend to give up bonding electrons and form crystals with high
lattice energies with oxygen.
D) oxides because oxygen, with its high electronegativity, forms strong covalent
bonds with them.
E) none of the above
Chapter 22: The Elements in Nature and Industry
6. The process in which a gaseous substance is converted into a condensed, more usable
chemical substance is called
A) differentiation. D) deposition.
B) liquefaction. E) remediation.
C) fixation.
7. The atmosphere contains about 700. billion metric tons of carbon in the form of carbon
dioxide. In the carbon cycle, about 200. billion metric tons of carbon (as carbon dioxide) enters
the atmosphere each year. Assuming that 200. billion metric tons of carbon also leaves the
atmosphere annually, how many years does the average carbon atom spend in the atmosphere in
each cycle?
A) 0.29 years
B) 3.5 years
C) 500. years
D) 140,000 years
E) More information is needed in order to calculate the answer.
8. Nitrogen fixation occurs through atmospheric, industrial, and biological processes.
Which of these fixes the most nitrogen?
A) biological D) industrial atmospheric
B) atmospheric E) industrial biological
C) industrial
9. When nitrogen undergoes atmospheric fixation, it enters the sea and land in the form of
A) NO. B) NO2. C) NH3. D) NO3–. E) NH4+.
10. What are the main mineral sources of phosphorus?
A) phosphides D) phosphates
B) phosphites E) elemental phosphorus
C) phosphors
11. Plants extract phosphate from the soil
A) by converting it to the dihydrogen phosphate ion by addition of acid to the soil
near roots.
B) by converting it to phosphoric acid.
C) by osmosis.
D) by leaching.
E) by fixation.
Chapter 22: The Elements in Nature and Industry
12. The most common source for commercial production of aluminum is called
A) aluminite. B) hematite. C) galena. D) cinnabar. E) bauxite.
13. The most common source for commercial production of sodium is called
A) sodalite. B) limestone. C) halite. D) galena. E) pyrite.
14. The process that selectively extracts a metal from its ore, by dissolving it, is called
A) roasting. B) leaching. C) smelting. D) flotation. E) hydration.
15. The process of converting metal sulfides to metal oxides is called
A) roasting. B) smelting. C) reduction. D) leaching. E) oxidation.
16. The debris accompanying a mineral is called
A) slag. B) gangue. C) ore. D) halite. E) ash.
17. The process used to produce silicon with a purity of more than 99.999999% is called
A) zone refining. D) sublimation.
B) electrorefining. E) alloying.
C) distillation.
18. Pyrometallurgy uses __________________ to separate a metal from its ore.
A) solid phase chemical properties D) aqueous chemical processes
B) electrical processes E) explosives
C) thermal processes
19. Electrometallurgy uses _________________ to separate a metal from its ore.
A) solid phase chemical properties D) aqueous chemical processes
B) electrical processes E) molten salt processes
C) thermal processes
20. Hydrometallurgy uses __________________ to separate a metal from its ore.
A) solid phase chemical properties D) aqueous chemical processes
B) electrical processes E) molten salt processes
C) thermal processes
Chapter 22: The Elements in Nature and Industry
21. Alloying a metal is done to
A) make its extraction from its ore easier.
B) convert the metal to an oxide.
C) disguise the true identity of the metal.
D) prepare ultrapure metal samples.
E) enhance properties like conductivity.
22. What elements are alloyed to make stainless steel?
A) Fe and C
B) Fe and Mn
C) Fe and Ni
D) Cr and C
E) Fe, Cr, and Ni
23. The final step of the purification of copper involves electrorefining in which copper is
separated from nickel and iron by being reduced at the cathode of a cell. Why are nickel and
iron not reduced?
A) Their reduction potentials are more positive than copper’s.
B) Their reduction potentials are more negative than copper’s.
C) They cannot be deposited on a copper electrode.
D) Their reduction potentials are more negative than water’s.
E) Their reduction requires large overvoltages.
24. The ______________ process uses a boiling 30% sodium hydroxide solution to treat
bauxite.
A) Bayer B) Hall-Heroult C) Dow D) Frasch E) Haber
25. The Hall-Heroult process refers to
A) the production of aluminum by electrolysis.
B) the recovery of sulfur from underground deposits.
C) the manufacture of sulfuric acid.
D) the production of ammonia from nitrogen and hydrogen gases.
E) the isolation of Al2O3 from bauxite.
Chapter 22: The Elements in Nature and Industry
26. Cryolite, Na3AlF6, is used in the electrolysis of aluminum oxide because
A) it is a good source of fluoride ions.
B) it reduces the energy requirement of the process, due to its low melting point.
C) it provides a source of fluorine, an oxidizing agent.
D) it provides a source of sodium, a reducing agent.
E) it is very soluble in water.
27. Which one of the following species or compounds reacts at the cathode in the Hall-
Héroult process?
A) Al2O3 B) Al(OH)3 C) F– D) AlF63- E) C
28. What gas is produced during the Hall-Héroult process for production of aluminum?
A) chlorine, Cl2 D) ammonia, NH3
B) oxygen, O2 E) carbon dioxide, CO2
C) hydrogen, H2
29. The kinetic isotope effect is the basis for
A) the radioactivity of tritium.
B) isolation of pure D2O.
C) tritium’s high reactivity.
D) the increase in boiling point when comparing hydrogen, deuterium, and tritium.
E) nuclear power generation.
30. Which of the following reactions is a good small-scale laboratory method for preparation
of hydrogen?
A) CH4(g) + H2O(g) → CO(g) + 3H2(g)
B) 3FeCl2(s) + 4H2O(g) → Fe3O4(s) + 6HCl(g) + H2(g)
C) NaH(s) + H2O(l) → NaOH(aq) + H2(g)
D) CO(g) + H2O (g) → CO2(g) + H2(g)
E) None of the above methods is useful.
31. The Downs cell is used in the production of
A) copper. B) hydrogen. C) iron. D) magnesium. E) sodium.
Chapter 22: The Elements in Nature and Industry
32. Calcium oxide is added to molten iron in the production of carbon steel in order to
A) convert silicon and phosphorus oxides to slag which can be decanted from the
molten steel.
B) serve as a scrubber to remove sulfur dioxide from the gases leaving the furnace.
C) remove any traces of acid which could weaken the steel.
D) add a small amount of oxygen to the steel to prevent corrosion and increase its
strength.
E) create gangue.
33. The alkali metals are isolated from non-aqueous systems. Why is this necessary?
A) The electrolysis of aqueous solutions of the alkali metals requires more energy
than electrolysis of the molten salts.
B) The dissolved alkali earth halides are too reactive to be electrolyzed.
C) The aqueous metal ions are more difficult to reduce than water.
D) The reduction potentials of the alkali metals are more positive than the reduction
potential of water.
E) The aqueous metal ions react violently with water.
34. Electrolysis is used as the last step in isolating pure __________________.
A) iron B) boron C) aluminum D) selenium E) carbon
35. The Frasch process is used to
A) convert aluminum oxide to metallic aluminum.
B) convert copper ore to copper sulfide.
C) mine magnesium.
D) mine elemental sulfur.
E) produce sodium metal.
36. Sulfur trioxide is the anhydride of sulfuric acid. However, SO3 is not added directly to
water during the synthesis of sulfuric acid because
A) hydration of SO3 is very exothermic and difficult to control.
B) hydration of SO3 is very endothermic and proceeds too slowly to be profitable.
C) at high temperatures water vapor catalyzes polymerization of SO3.
D) vapor phase sulfuric acid is corrosive and limits the useful life of the reactor.
E) the water would decompose under such conditions.
Chapter 22: The Elements in Nature and Industry
37. The main end use of sulfuric acid is
A) manufacture of iron and steel.
B) processing of petroleum.
C) production of fertilizers.
D) production of explosives.
E) production of various other chemicals.
38. The chlor-alkali process produces chlorine, Cl2(g), in large quantities. What other
industrially important substances are produced in this process?
A) Na(s), H2(g) D) Na(s), O2(g)
B) H2(g), O2(g) E) NaOH(aq), H2(g)
C) Hg(l), NaCl(s)
39. Describe, and give reasons for, the fundamental bonding differences between transition
metal sulfides and transition metal oxides.
40. Give two important reasons why there is so much more Na+ in the oceans than K+,
41. The mass of the atmosphere has been estimated to be 5.2 × 1021 g, while the average
molar mass of atmospheric gases is 28.9 g/mol. If the concentration of carbon dioxide in the
atmosphere is 360 ppm by volume, calculate the mass of this gas in the atmosphere, in billions
of metric tons, bmt. (1 bmt = 1012 kg)
Chapter 22: The Elements in Nature and Industry
42. Briefly describe the three main pathways for nitrogen fixation.
HNO3, from atmospheric N2, O2, and H2O. Write balanced chemical equations to represent the
three reactions involved in the formation of HNO3 by this route.
44. The leaching of gold can be represented by the equation
4Au(s) + O2(s) + 8CN–(aq) + 2H2O(l) → 4Au(CN)2–(aq) + 4OH–(aq)
In this reaction, identify the oxidant, the reductant and the oxidation numbers of the elements
which change.
45. What gas is produced at the anode in the Downs cell, in which molten NaCl is
electrolyzed?
46. Potassium is produced industrially by the reaction
Na(l) + K+(l) Na+(l) + K(g)
The reaction is carried out at 850°C, but the equilibrium Kc constant strongly favors the
reactants. Explain how the conditions are manipulated to ensure a good yield of potassium
despite the small value of Kc.
Chapter 22: The Elements in Nature and Industry
47. In the commercial production of aluminum metal, the final stage involves the reaction
2Al2O3(in molten Na3AlF6) + 3C(graphite) → 4Al(l) + 3CO2(g)
Briefly outline the method and equipment with which the reaction is accomplished.
48. What gas is produced at the anode in the Hall-Heroult process for the electrolytic
production of aluminum?
49. Aluminum and magnesium form are light metals which are used in many structural
applications. Although they are highly active metals (as their electrode potentials suggest), they
can often be used without the use of paint or other applied finishes to protect them against
corrosion. How is this possible?
50. Compared to the asbestos diaphragm-cell used in the chlor-alkali process, list
a. one main advantage and one disadvantage of mercury cells.
b. two important advantages of polymer membrane-cells.
51. Sulfide ores are frequently treated by flotation in order to concentrate them.
52. Carbon atoms in the carbon cycle spend most of their time in the oceans.
53. The industrial production of ammonia from nitrogen and hydrogen accounts for a greater
amount of nitrogen fixation than either the atmospheric or the biological pathways.
54. The purpose of anodizing aluminum is to remove the oxide layer from the metal’s
surface.
Chapter 22: The Elements in Nature and Industry
55. In the electrolysis of water, the hydrogen gas evolved at the cathode is enriched in
deuterium (hydrogen-2), compared to the more common isotope, protium (hydrogen-1).
56. The bond energy in the hydrogen molecule (H2) is greater than that of the tritium
molecule (T2).
57. Hydrogen displays the largest kinetic isotope effect of all the elements.
58. In the industrial electrolysis of aqueous NaCl (the chlor-alkali process), the modern trend
is toward the use of cells incorporating polymer membranes to separate the anode and cathode
solutions.