Deck 22: Inorganic Materials

Question 1

The primary building blocks in silicates are

A) C-O bonds
B) Si-C bonds
C) Si-O bonds
D) Si-Si bonds
E) None of the above

Answer 1

C

Question 2

Feldspars are a type of

A) aluminosilicate
B) clay
C) silicate
D) zeolite
E) none of the above

Answer 2

A

Question 3

Asbestos is a type of

A) aluminosilicate
B) clay
C) silicate
D) zeolite
E) none of the above

Answer 3

C

Question 4

Of the following, which is most likely to be used as a catalyst?

A) aluminosilicate
B) clays
C) silicates
D) zeolites
E) none of the above

Question 5

Which of the following is the result of firing a ceramic?

A) densification
B) sintering
C) doping
D) a and b
E) b and c

Question 6

Slowly heating an object under strain so that it cools slowly is called

A) densification
B) sintering
C) doping
D) annealing
E) a and b

Question 7

Which of the following has the highest conductivity?

A) silver
B) gold
C) platinum

Question 8

Hydraulic cement hardens by

A) forcing water out of the structure with great pressure.
B) Incorporating water into the structure
C) Forming hydroxides
D) b and c
E) none of the above

Question 9

A refractory is

A) a ceramic material that withstands temperatures of up to 1500°C without melting.
B) a conducting material that dissipates small amounts of heat.
C) a device used to separate various types of silicates.
D) a device for converting AC current to DC current.
E) none of the above

Question 10

Conductivity, L_m, has units of

A) V·A^-1
B) W·m
C) W^-1·m^-1
D) A·m^-2

Question 11

Mobility, m, has units of

A) A·m²
B) m²·V^-1·s^-1
C) m²·V^-2·s^-1
D) V·m^-2·s^-1

Question 12

Which lies energetically lower?

A) conduction band
B) valence band

Question 13

The conductivity of semiconductors can be increased by

A) increasing the temperature.
B) decreasing the temperature.
C) using electromagnetic radiation for move electrons from the conduction band to the valence band.
D) a and c
E) b and c

Question 14

When silicon is doped with a group V element

A) electrons move slower across the band gap.
B) more electrons than those needed for bonding are added to the crystal.
C) the donor impurity decreases the conductivity.
D) all of the above
E) none of the above

Question 15

When either n- or p-type doping is used with silicon, conductivity decreases compared to that of pure silicon at the same temperature.

Question 16

Perovskites typically have ________ different metals for every 3 oxygen atoms.

A) 1
B) 2
C) 3
D) 4

Question 17

Perovskites can become superconductors at

A) high temperatures
B) low temperatures
C) room temperature
D) a and b
E) none of the above

Question 18

Exhibit 22-1
The following question(s) pertain to GaAs, which has a band gap of 140 kJ·mol.
Refer to Exhibit 22-1. What temperature is required to thermally excite electrons from the valence band to the conduction band?

A) 14000 K
B) 15890 K
C) 16840 K
D) 22180 K

Question 19

Exhibit 22-1
The following question(s) pertain to GaAs, which has a band gap of 140 kJ·mol.
Refer to Exhibit 22-1. What is the longest wavelength of radiation is required to cause this transition?

A) 932 nm
B) 854 nm
C) 727 nm
D) 595 nm

Question 20

A sample of CdS has to be heated to 30411 K to thermally excite electrons from the valence band to the conduction band. What is the value of E_g based on these experiments?

A) 3.2×10^-19 J
B) 6.3×10^-19 J
C) 4.2×10^-19 J
D) 8.7×10^-19 J

Question 21

A sample of CdS is doped with Tellurium. This will

A) form an n-type semiconductor.
B) form a p-type semiconductor.
C) create a "hole" in the valence band.
D) a and c
E) b and c

Question 22

Which of the following will have the greatest mobility?

A) Li⁺
B) Mg²⁺
C) Ca²⁺
D) Ba²⁺

Question 23

Compared to a semiconductor, the band gap in an insulator is

A) larger
B) approximately the same
C) smaller, but still present
D) negligible

Question 24

Exhibit 22-2
The following question(s) pertain to the following equation which estimates the number of electrons per cubic centimeter excited to the conduction band as a function of temperature and the band gap energy. Refer to Exhibit 22-2. Based solely on the equation above, which set of conditions will result in the most electrons being excited to the conduction band.

A) Low temperature, low band gap energy
B) Low temperature, high band gap energy
C) High temperature, low band gap energy
D) High temperature, high band gap energy

Question 25

Exhibit 22-2
The following question(s) pertain to the following equation which estimates the number of electrons per cubic centimeter excited to the conduction band as a function of temperature and the band gap energy. Refer to Exhibit 22-2. The band gap of pure crystalline silicon is 1.94×10^-19 J at 300 K. How many electrons are excited from the valence band to the conduction band at this temperature in a 1.00 cm³ silicon crystal?

A) 1.70×10⁹
B) 4.80×10¹⁵
C) 0.555 N_A
D) 1.46×10⁷

Question 26

Silicon, a semiconductor, has four valence electrons. Titanium, a conductor, also has four valence electrons. Despite both having four electrons, the elements differ in their conductivity because

A) Ti atoms are smaller than Si atoms
B) The band gap energies fall sharply in from the third period to the fourth period on the periodic table
C) Ti has low-lying d orbitals that form a conduction band, Si does not
D) Ti has a larger ionization energy that Si
E) None of the above.

Question 27

The silicon to oxygen bonds in silicates are

A) Purely ionic
B) Purely covalent
C) Mainly covalent with partial ionic character
D) Mainly ionic with partial covalent character
E) metallic

Question 28

Portland cement hardens through a series of complex reactions. It normally sets in a matter of ______ but may take as long as a ______ to attain its final strength.

A) minute, day
B) hours, month
C) hours, week
D) hours, year
E) week, month

Question 29

The high conductivity of metals is ascribed to

A) empty conduction bands
B) filled conduction bands
C) empty valence orbitals
D) filled valence orbitals
E) partially filled conduction band

Question 30

Doping silicon with indium increases its conductivity by creating

A) an n-type semiconductor
B) holes in the conduction band
C) holes in the valence band
D) None of these

Question 31

Glasses can be described as

A) anisotropic
B) isotropic
C) doped
D) B and C
E) none of the above

Question 32

The higher silicate structures are formed from the orthosilicate ion that has a _________ geometry.

A) square planar
B) trigonal bipyramid
C) octahedral
D) triangular
E) none of the above

Question 33

In quartz crystals, what is the formal charge on the Si atom?

A) 0
B) 8
C) -2
D) 4
E) none of the above