Deck 22: The Elements in Nature and Industry

Question 1

Pyrometallurgy uses __________________ to separate a metal from its ore.

A) solid phase chemical properties
B) electrical processes
C) thermal processes
D) aqueous chemical processes
E) explosives

Answer 1

thermal processes

Question 2

Hydrometallurgy uses __________________ to separate a metal from its ore.

A) solid phase chemical properties
B) electrical processes
C) thermal processes
D) aqueous chemical processes
E) molten salt processes

Answer 2

aqueous chemical processes

Question 3

The Earth's core consists mainly of

A) Ni.
B) O.
C) Al.
D) Si.
E) Fe.

Answer 3

Fe.

Question 4

Electrometallurgy uses _________________ to separate a metal from its ore.

A) solid phase chemical properties
B) electrical processes
C) thermal processes
D) aqueous chemical processes
E) molten salt processes

Question 5

The process used to produce silicon with a purity of more than 99.999999% is called

A) zone refining.
B) electrorefining.
C) distillation.
D) sublimation.
E) alloying.

Question 6

The most common source for commercial production of sodium is called

A) sodalite.
B) limestone.
C) halite.
D) galena.
E) pyrite.

Question 7

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

Question 8

What are the main mineral sources of phosphorus?

A) phosphides
B) phosphites
C) phosphors
D) phosphates
E) elemental phosphorus

Question 9

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.

Question 10

Nitrogen fixation occurs through atmospheric, industrial, and biological processes. Which of these fixes the most nitrogen?

A) biological
B) atmospheric
C) industrial
D) industrial $\approx$ atmospheric
E) industrial $\approx$ biological

Question 11

The debris accompanying a mineral is called

A) slag.
B) gangue.
C) ore.
D) halite.
E) ash.

Question 12

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.

Question 13

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⁺.

Question 14

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.

Question 15

The most abundant element in the Earth's crust is

A) H.
B) Fe.
C) Al.
D) Si.
E) O.

Question 16

The most common source for commercial production of aluminum is called

A) aluminite.
B) hematite.
C) galena.
D) cinnabar.
E) bauxite.

Question 17

The process of converting metal sulfides to metal oxides is called

A) roasting.
B) smelting.
C) reduction.
D) leaching.
E) oxidation.

Question 18

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.

Question 19

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.

Question 20

The process in which a gaseous substance is converted into a condensed, more usable chemical substance is called

A) differentiation.
B) liquefaction.
C) fixation.
D) deposition.
E) remediation.

Question 21

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)

Question 22

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.

Question 23

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.

Question 24

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)
B) H₂(g), O₂(g)
C) Hg(l), NaCl(s)
D) Na(s), O₂(g)
E) NaOH(aq), H₂(g)

Question 25

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.

Question 26

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.

Question 27

The ______________ process uses a boiling 30% sodium hydroxide solution to treat bauxite.

A) Bayer
B) Hall-Heroult
C) Dow
D) Frasch
E) Haber

Question 28

What gas is produced during the Hall-Héroult process for production of aluminum?

A) chlorine, Cl₂
B) oxygen, O₂
C) hydrogen, H₂
D) ammonia, NH₃
E) carbon dioxide, CO₂

Question 29

Give two important reasons why there is so much more Na⁺ in the oceans than K⁺, despite their similar abundances in the earth's crust.

Question 30

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.

Question 31

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) AlF₆^3-
E) C

Question 32

Describe, and give reasons for, the fundamental bonding differences between transition metal sulfides and transition metal oxides.

Question 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.

Question 34

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.

Question 35

Electrolysis is used as the last step in isolating pure __________________.

A) iron
B) boron
C) aluminum
D) selenium
E) carbon

Question 36

Which of the following reactions is a good small-scale laboratory method for preparation of hydrogen?

A) CH₄(g) + H₂O(g) $\to$ CO(g) + 3H₂(g)
B) 3FeCl₂(s) + 4H₂O(g) $\to$ Fe₃O₄(s) + 6HCl(g) + H₂(g)
C) NaH(s) + H₂O(l) $\to$ NaOH(aq) + H₂(g)
D) CO(g) + H₂O (g) $\to$ CO₂(g) + H₂(g)
E) None of the above methods is useful.

Question 37

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

Question 38

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.

Question 39

The Downs cell is used in the production of

A) copper.
B) hydrogen.
C) iron.
D) magnesium.
E) sodium.

Question 40

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.

Question 41

What gas is produced at the anode in the Downs cell, in which molten NaCl is electrolyzed?

Question 42

Carbon atoms in the carbon cycle spend most of their time in the oceans.

Question 43

The leaching of gold can be represented by the equation
4Au(s) + O₂(s) + 8CN^-(aq) + 2H₂O(l) $\to$ 4Au(CN)₂^-(aq) + 4OH^-(aq)
In this reaction, identify the oxidant, the reductant and the oxidation numbers of the elements which change.

Question 44

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.

Question 45

Briefly describe the three main pathways for nitrogen fixation.

Question 46

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).

Question 47

Hydrogen displays the largest kinetic isotope effect of all the elements.

Question 48

Sulfide ores are frequently treated by flotation in order to concentrate them.

Question 49

What gas is produced at the anode in the Hall-Heroult process for the electrolytic production of aluminum?

Question 50

In the commercial production of aluminum metal, the final stage involves the reaction
2Al₂O₃(in molten Na₃AlF₆) + 3C(graphite) $\to$ 4Al(l) + 3CO₂(g)
Briefly outline the method and equipment with which the reaction is accomplished.

Question 51

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.

Question 52

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.

Question 53

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?

Question 54

The bond energy in the hydrogen molecule (H₂) is greater than that of the tritium molecule (T₂).

Question 55

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 K_c constant strongly favors the reactants. Explain how the conditions are manipulated to ensure a good yield of potassium despite the small value of K_c.

Question 56

Lightning, fires, and other atmospheric processes result in the formation of nitric acid, 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.

Question 57

The purpose of anodizing aluminum is to remove the oxide layer from the metal's surface.