Deck 20: Metallurgy and the Chemistry of Metals

Question 1

A naturally occurring substance with a range of chemical composition is

A)an element.
B)a mineral.
C)gangue.
D)an ore.
E)an amalgam.

Answer 1

a mineral.

Question 2

The flotation process used in metallurgy involves

A)the roasting of sulfides.
B)separation of gangue from ore.
C)electrolytic reduction..
D)chemical reduction of a metal.
E)zone refining.

Answer 2

separation of gangue from ore.

Question 3

According to the band theory, which of these statements provide(s)an explanation for the high electrical conductivity of metals? I.a partly filled conduction band
II.a valence band overlapping an empty conduction band
III.a filled valence band
IV.a large gap between the valence band and the conduction band

A)I and II
B)I and III
C)III
D)III and IV
E)IV

Answer 3

I and II

Question 4

The naturally occurring form of a metal that is concentrated enough to allow economical recovery of the metal is know as

A)an element.
B)a mineral.
C)gangue.
D)an ore.
E)an amalgam.

Question 5

Alloys of iron that contain 1.0-1.5% carbon and some manganese, phosphorus, silicon, and sulfur are called

A)steel.
B)cast iron.
C)coke.
D)pig iron.
E)hematite.

Question 6

Volatile impurities are removed from ores by means of

A)roasting.
B)amalgamation.
C)electrolysis.
D)flotation.
E)zone refining.

Question 7

Metallic sodium is obtained commercially from molten sodium chloride by

A)chemical reduction with magnesium.
B)flotation.
C)electrolysis.
D)zone refining.
E)roasting.

Question 8

In p-type semiconductors,

A)the semiconductors are "ultra purified" to increase conductivity.
B)the valence and conduction bands are formed exclusively from "p orbitals."
C)the semiconductors are "patented" for use in commercial applications.
D)acceptor impurities are added to provide "positive holes" that increase the electrical conductivity of the semiconductor.

Question 9

Which one of these elements would give a p-type semiconductor when added to a silicon crystal?

A)C
B)P
C)As
D)Ga
E)Sb

Question 10

In the Mond process, nickel is purified by

A)dissolving the crude ore in sulfuric acid, and precipitating the nickel(II)ion as the sulfate salt.
B)dissolving the crude ore in a lye (NaOH)solution, and precipitating the nickel(II)ion as the hydroxide salt.
C)heating the crude ore to its melting point and electrolytically reducing the nickel(II)ions to form the metal.
D)passing sodium gas over the crude ore at high temperatures, chemically reducing the nickel(II)to nickel metal.
E)passing carbon monoxide over the impure metal at high temperature, forming the volatile Ni(CO)₄ which is removed as a gas.

Question 11

In n-type semiconductors

A)the energy gap between the valence band and the conduction band is very large.
B)impurities that donate electrons are added to provide conduction electrons.
C)a valence band overlaps the empty conduction band.
D)impurities that provide "positive holes" are added to a pure semiconductor.

Question 12

Which one of these metals would normally be obtained by chemical reduction?

A)aluminum
B)calcium
C)lithium
D)sodium
E)vanadium

Question 13

Which of these reactions represents the removal of silica from iron ore in a blast furnace?

A)SiO₂(s) $\to$ SiO₂(g)
B)SiO₂(s)+ CaO(s) $\to$ CaSiO₃(l)
C)SiO₂(s)+ 4HF(g) $\to$ SiF₄(g)+ 2H₂O(g)
D)SiO₂(s)+ C(s) $\to$ Si(l)+ CO₂(g)
E)SiO₂(s)+ CO(g) $\to$ SiCO₃(l)

Question 14

Which of these elements when doped into silicon would give an n-type semiconductor?

A)C
B)Ga
C)P
D)Ge
E)B

Question 15

What effect does increasing temperature have on the conductivities of semiconductors?

A)increases
B)decreases
C)no change
D)cannot be predicted

Question 16

Which one of these metals would normally be obtained by electrolytic reduction?

A)aluminum
B)chromium
C)copper
D)iron
E)zinc

Question 17

In the Hall process, ____________ is reduced ____________.

A)nickel; electrolytically
B)aluminum; electrolytically
C)nickel; by reaction with metallic sodium
D)aluminum; by reaction with metallic sodium
E)copper; electrolytically

Question 18

All metals are solids at room temperature (25°C)except

A)Cs.
B)Cd.
C)Ga.
D)Hg.
E)Rb.

Question 19

According to the band theory, a band is

A)an elastic force that holds electrons close to atoms in an insulator.
B)the energy gap associated with semiconductors.
C)a large number of molecular orbitals that are close together in energy.
D)a large number of atoms in a crystal.

Question 20

The principal reducing agent in a blast furnace is

A)CaO(s)
B)CaSiO₃(l)
C)CO(g)
D)O₂(g)
E)CO₂(g)

Question 21

The mineral cryolite, Na₃AlF₆, is used in the Hall process for aluminum production as

A)the source of aluminum (the ore).
B)a chemical reducing agent.
C)a material that forms a slag and thus removes impurities.
D)a solvent for alumina, Al₂O₃.

Question 22

The Hall process involves the reduction of Al₂O₃ to aluminum by

A)carbon (coke).
B)carbon monoxide.
C)molecular hydrogen.
D)sodium.
E)electrolysis.

Question 23

In Al₂Cl₆, the geometry of the molecule at each aluminum atom is

A)trigonal planar
B)tetrahedral
C)trigonal pyramidal
D)square planar
E)octahedral

Question 24

Which of the following it not true comparing aluminum to copper?

A)Aluminum is cheaper than copper.
B)Aluminum is lighter than copper.
C)Aluminum is a better conductor of electricity than copper.
D)Aluminum is easier to oxidize than copper.

Question 25

Aluminum hydroxide, Al(OH)₃, is

A)an acid.
B)an amphoteric hydroxide.
C)a base.
D)an explosive hydroxide.
E)used to make amalgams.

Question 26

Which one of these elements has seawater as its commercial source?

A)Mg
B)Al
C)Ca
D)Sn
E)Cd

Question 27

For the reaction 3Fe(s)+ C(s) Fe₃C(s), $\Delta$ H° = 21 kJ/mol and $\Delta$ S° = 20.4 J/mol·K at 25°C. Estimate the minimum temperature above which the formation of cementite (Fe₃C)is favored.

A)1.0°C
B)970°C
C)700°C
D)1000°C
E)760°C

Question 28

Which of these statements does not describe a property of aluminum?

A)Al is an efficient electrical conductor.
B)Al has a low density compared to other metals.
C)Al forms an amphoteric hydroxide.
D)Al is generally considered toxic to humans.
E)Al has a great affinity for oxygen.

Question 29

Calcium metal is produced by electrolysis of

A)CaSO₄
B)CaF₂
C)CaCO₃
D)Ca(OH)₂
E)CaCl₂

Question 30

Basic properties are characteristic of all alkaline earth metal oxides except one. The formula of this exception is

A)BeO
B)MgO
C)SO₂
D)B₂O₃
E)CaO

Question 31

Which element group includes the most reactive of all the metallic elements?

A)alkali metals
B)alkaline earth metals
C)coinage metals (Group 1B)
D)transition metals
E)Group 2B metals

Question 32

Write the chemical formula of calcite.

Question 33

Which two compounds are produced by the Solvay process?

A)CaCO₃ and CaO
B)CaCO₃ and Na₂CO₃
C)NaHCO₃ and NaCl
D)NH₃ and NH₄Cl
E)NaHCO₃ and Na₂CO₃

Question 34

The equilibrium 3Fe(s)+ C(s) Fe₃C(s)is established in a solid solution. For such a solution, one can write an equilibrium constant in the usual way except that here one has concentrations that refer to solids in the solid solution. Determine the equilibrium constant for the formation of cementite from iron and carbon at 680°C.(Given: for this reaction at 25°C, $\Delta$ H° = 21 kJ/mol and $\Delta$ S° = 20.4 J/mol·K)

A)0.75
B)0.33
C)3.1
D)0.82
E)1.2

Question 35

Which one of these species is an example of a basic oxide?

A)SO₃(g)
B)BaO(s)
C)Al₂O₃(s)
D)Fe₂O₃(s)
E)SiO₂(s)

Question 36

Aluminum is an active metal, but does not corrode as iron does because

A)Al does not react with O₂.
B)a protective layer of Al₂O₃ forms on the metal surface.
C)Al is harder to oxidize than is Fe.
D)the enthalpy of formation of aluminum oxide is negative.
E)aluminum has a high tensile strength.

Question 37

Which choice gives two raw materials used in the Solvay process?

A)NaHCO₃ and NaCl
B)CaCO₃ and Na₂CO₃
C)NaCl and NaCO₃
D)NH₃ and NaCl
E)Na₂CO₃ and NH₄Cl

Question 38

In the production of potassium metal, the source of electrons in the reduction of K⁺ ions is

A)H₂(g)
B)Na(g)
C)CO(g)
D)CaO(s)
E)electrolysis

Question 39

Write the chemical formula of epsomite (sold in pharmacies as Epsom salts).

Question 40

Which of these ions is most likely to substitute for Ca²⁺ in the human body?

A)Cl^-
B)Sr²⁺
C)K⁺
D)S^2-
E)Pb²⁺

Question 41

Write a balanced chemical equation illustrating roasting.

Question 42

The following reaction is used to produce titanium metal at high temperature.
TiCl₄(g)+ 2Mg(l) $\to$ Ti(s)+ 2MgCl₂(l)
Which element is oxidized and which is reduced?

Question 43

Beryllium, the first element in Group 2A, is the most metallic element in the group.

Question 44

Write the chemical formula of corundum.

Question 45

Write a balanced chemical equation illustrating chemical reduction.

Question 46

Cast iron as it is prepared in a blast furnace is a product of high purity.

Question 47

Mercury, magnesium, and zinc have low enough boiling points that they can be purified by distillation.

Question 48

Write the chemical formula of dolomite that provides a source for both magnesium and calcium.

Question 49

Potassium superoxide, KO₂(s), is used in the breathing systems of biohazard suits.Write separate chemical equations showing how KO₂(s)reacts with moisture and carbon dioxide in exhaled air to generate oxygen gas.

Question 50

Write the chemical formula of fluorite.

Question 51

Write the chemical formula of magnetite.

Question 52

The following reaction is used to produce chromium metal at high temperature.
Cr₂O₃(s)+ 2Al(s) $\to$ 2Cr(l)+ Al₂O₃(s)
Which element is oxidized and which is reduced?

Question 53

Write two balanced chemical equations for the burning of magnesium in air.

Question 54

Three means used to concentrate ores are flotation, ferromagnetic separation, and amalgamation.

Question 55

Write the chemical formula of halite.

Question 56

Why is cryolite, Na₃AlF₆, mixed with alumina prior to electrolysis in the production of Al?

Question 57

Write the chemical formula of pyrite.

Question 58

Bauxite (Al₂O₃·2H₂O)ore is the principal commercial source of aluminum metal.