Question 1

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

Accepted Answer

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

Question 2

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.

Accepted Answer

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

Question 3

The Hall process involves the reduction of Al2O3 to aluminum by

Accepted Answer

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

Question 4

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

Accepted Answer

It acts is

Question 5

In n-type semiconductors

Accepted Answer

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. 
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 6

In p-type semiconductors,

Accepted Answer

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. 
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 7

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)

Accepted Answer

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

Question 8

Write the chemical formula of fluorite.

Accepted Answer

The answer of Write the chemical formula of fluorite....

Question 9

Write the chemical formula of corundum.

Accepted Answer

The answer of Write the chemical formula of corundum....

Question 10

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

Accepted Answer

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

Question 11

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

Accepted Answer

A) Cl- 
B) Sr2+ 
C) K+ 
D) S2- 
E) Pb2+ 
A) Cl- 
B) Sr2+ 
C) K+ 
D) S2- 
E) Pb2+

Question 12

The principal reducing agent in a blast furnace is

Accepted Answer

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

Question 13

In the Mond process, nickel is purified by

Accepted Answer

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. 
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 14

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

Accepted Answer

A) True 
 B)False

Question 15

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

Accepted Answer

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

Question 16

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

Accepted Answer

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

Question 17

Volatile impurities are removed from ores by means of

Accepted Answer

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

Question 18

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

Accepted Answer

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

Question 19

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

Accepted Answer

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) 
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 20

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

Accepted Answer

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

Exam 20: Metallurgy and the Chemistry of Metals

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

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

The Hall process involves the reduction of Al2O3 to aluminum by

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

In n-type semiconductors

In p-type semiconductors,

Write the chemical formula of fluorite.

Write the chemical formula of corundum.

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

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

The principal reducing agent in a blast furnace is

In the Mond process, nickel is purified by

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

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

Volatile impurities are removed from ores by means of

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

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

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

Chemistry: The Study of Change

Atoms, Molecules, and Ions

Mass Relationships in Chemical Reactions

Reactions in Aqueous Solution

Gases

Thermo-Chemistry

Quantum Theory and the Electronic Structure of Atoms

Periodic Relationships Among the Elements

Chemical Bonding I: Basic Concepts

Chemical Bonding Ii: Molecular Geometry and Hybridization of Atomic Orbitals

Intermolecular Forces and Liquids and Solids

Physical Properties of Solutions

Chemical Kinetics

Chemical Equilibrium

Acids and Bases

Acid-Base Equilibria and Solubility Equilibria

Chemistry in the Atmosphere

Entropy, Free Energy, and Equilibrium

Electrochemistry

Nonmetallic Elements and Their Compounds

Transition Metal Chemistry and Coordination Compounds

Nuclear Chemistry

Organic Chemistry

Synthetic and Natural Organic Polymers

Filters

The Hall process involves the reduction of Al₂O₃ to aluminum by

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

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

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