11) Which metal is not found in nature in uncombined form?
A) Mn
B) Au
C) Os
D) Ir
12) Which of the following elements is most likely to occur as a metal sulfide ore?
A) Al
B) Hg
C) Li
D) Mn
13) Which of the following elements is most likely to naturally occur as a carbonate?
A) Ba
B) Cu
C) Au
D) Pd
14) What is the concentration process used to separate chalcopyrite (CuFeS2) from its gangue?
A) chemical treatment
B) density differences
C) floatation process
D) magnetic differences
15) The chemical process of roasting is commonly used to facilitate the reduction of which metal ores?
A) Ag, Cu, and Hg
B) Ag, Mg, and Na
C) Hg and Pt
D) Ag, Mn, and V
16) Which of the following metals is commonly obtained by electrolysis?
A) Pt
B) Ag
C) Ni
D) Na
17) Which element is likely to be a principal impurity in zinc ore?
A) lead
B) zinc
C) silver
D) cadmium
18) How many kilograms of copper sulfide must be reduced to produce 3.20 × 1010 kg of Cu? The
reduction of copper proceeds via the following reaction.
Cu2S (l) + O2 (g) 2Cu (l) + SO2 (g)
A) 3.20 × 1013 kg
B) 4.0 × 1012 kg
C) 6.4 × 1010 kg
D) 1.3 × 1011 kg
19) Steel is a mixture composed primarily of
A) iron and chromium.
B) iron and zinc.
C) iron and lead.
D) iron and gold.
20) What is a primary ingredient used in the production of iron by the blast furnace process?
A) bromide
B) sulfate
C) sulfide
D) limestone
21) Which substance is the best conductor of electricity?
A) bromine
B) diamond
C) tungsten
D) xenon
22) Which one of the following metals is expected to have the highest melting point?
A) Au
B) Fe
C) Hg
D) Zn
23) Which element has the smallest energy band gap?
A) I
B) Se
C) Sn
D) Te
24) Which one of the following is an electrical insulator?
A) alumina
B) geranium doped with antimony
C) gold
D) tellurium
25) Which of the following is a semiconductor?
A) Ca
B) B
C) K
D) Pb
26) What is the average oxidation number of Cu in the 1–2-3 superconductor YBa2Cu3O7 if Y is in the +3
oxidation state?
A) +2
B) +2.33
C) +0.67
D) +4.33
27) What element was found to be the first superconductor of electricity at 4.2 K in 1911?
A) nickel
B) aluminum
C) gallium
D) mercury
28) What substance has a rating of 10 on the Mohs hardness scale?
A) beryllia
B) silicon carbide
C) diamond
D) aluminum
29) What is not generally considered to be a ceramic?
A) silicon, Si
B) zirconia, ZiO2
C) silicon carbide, SiC
D) silicon nitride, Si3N4
30) What is the coordination number of Si in SiC that has a diamond-like structure?
A) 1
B) 2
C) 4
D) 6
21.3 Short Answer Questions
1) What is the oxidation number of mercury in cinnabar?
2) One source of titanium is pyrophanite, MnTiO3. The oxidation states of manganese and titanium in
pyrophanite are ________ and ________, respectively.
3) The principal source of chromium is chromite. What is the formula of chromite?
4) The balanced chemical equation for the production of silver by roasting of its sulfide is ________.
5) Copper can be obtained from its copper(I) sulfide ore by roasting. What is the balanced equation for
the roasting of copper(I) sulfide?
6) Write a balanced chemical equation for obtaining iron metal by the reduction of hematite, Fe2O3, by
hydrogen gas.
7) Al2O3 can be separated from iron oxide impurities in bauxite by dissolving the Al2O3 in hot aqueous
NaOH. Give the formula of the aluminum complex ion that forms, and write a balanced net ionic
equation for its formation by the reaction between Al2O3 and NaOH.
8) During the production of iron, the formation of CaSiO3 (slag) from the reaction of CaO (lime) and
SiO2 (sand), shown below, facilitates the separation of the iron from the gangue.
CaO(s) + SiO2(s) → CaSiO3(l)
In this reaction the acidic oxide is ________ and the basic oxide is ________.
9) The number of electrons that half fill a composite s–d band is ________.
10) According to band theory, the element having all of its bonding molecular orbitals filled and all of its
antibonding orbitals empty in the 4s-3d composite band is ________.
39
11) Tin exists in two forms: gray tin and white tin. The electrical conductivity of gray tin increases with an
increase in temperature, whereas the electrical conductivity of white tin decreases with an increase in
temperature. The form of tin that is a semiconductor is ________ tin.
12) Addition of a small amount of As impurity in silicon results in a(n) ________-type semiconductor that
has a conductivity that is ________ (greater, less) than silicon.
13) Addition of a small amount of Ga impurity in silicon results in a(n) ________-type semiconductor that
has a conductivity that is ________ (greater, less) than silicon.
14) A diode has a positive bias when the p-type semiconductor is attached to the ________ (negative,
positive) battery terminal, which ________ (inhibits, permits) electron flow.
15) A diode has a negative bias when the p-type semiconductor is attached to the ________ (negative,
positive) battery terminal, which ________ (inhibits, permits) electron flow.
16) Light emitting diodes (LEDs) used in automobile brake lights illuminate 200 milliseconds faster than
conventional incandescent brake lights. The faster illumination gives the driver of a trailing car an
additional stopping distance of ________ feet at 55 mph.
17) The wavelength of light emitted by the GaP0.40As0.60 LED, which has a band gap of 181 kJ/mol, is
________ nm.
18) An AlGaAs diode laser pointer emits 532 nm light and appears ________ (blue, green, red) in color.
19) In order for a photovoltaic cell to convert light to electricity, the band gap must be less than or equal
to the energy of the light absorbed. If light of 955 nm is to be absorbed, the band gap of the photovoltaic
cell must be less than or equal to ________ kJ/mol.
20) The superconductor Tl2Ba2Ca2Cu3O10 has a critical temperature Tc = 125 K. In order for each of the
atoms to have a whole-number oxidation number, the oxidation numbers of Tl, Ba, Ca, Cu, and O must
be ________, ________, ________, ________, and ________, respectively.
21) Nonoxide ceramics include silicon nitride, the formula of which is ________.
22) A silicon carbide ceramic has a unit cell with carbon atoms in a cubic closest packed arrangement with
carbon atoms occupying one-half of the tetrahedral holes. The empirical formula of this ceramic is
________.
23) Composite materials can be classified as ceramic-ceramic, ceramic-metal, or ceramic-polymer. Silicon
carbide-reinforced alumina is classified as ________.
24) Alumina-titanium is a composite material used in hip replacements. Composite materials can be
classified as ceramic-ceramic, ceramic-metal, or ceramic-polymer. Alumina-titanium is classified as
________.
25) Because nanoparticles have a larger percentage of atoms on the surface of the nanoparticle than on the
surface of bulk material, nanoparticles have ________ melting points and ________ chemical reactivity
than the bulk material.
26) A nanoparticle that exhibits a yellow color is (larger/smaller) ________ than a nanoparticle that
exhibits a red color.