Q&A Hero

Q: What is a principal commercial ore for the element aluminum? A) bauxite B) chalcopyrite C) chromite D) hematite

Q: What minerals are important commercial sources of metals? A) aluminosilicates and silicates B) chlorides and iodides C) nitrates and phosphates D) oxides and sulfides

Q: What are the most abundant minerals in the earth's crust? A) aluminosilicates and silicates B) chlorides and iodides C) nitrates and phosphates D) oxides and sulfides

Q: 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.

Q: 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 ________.

Q: Composite materials can be classified as ceramic-ceramic, ceramic-metal, or ceramic-polymer. Boron nitride/epoxy is classified as ________.

Q: 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 ________.

Q: Nonoxide ceramics include silicon nitride, the formula of which is ________.

Q: 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.

Q: 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.

Q: An AlGaAs diode laser pointer emits 532 nm light and appears ________ (blue, green, red) in color.

Q: The wavelength of light emitted by the GaP0.40As0.60 LED, which has a band gap of 181 kJ/mol, is ________ nm.

Q: 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.

Q: A diode has a negative bias when the p-type semiconductor is attached to the ________ (negative, positive) battery terminal, which ________ (inhibits, permits) electron flow.

Q: A diode has a positive bias when the p-type semiconductor is attached to the ________ (negative, positive) battery terminal, which ________ (inhibits, permits) electron flow.

Q: 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.

Q: 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.

Q: 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.

Q: 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 ________.

Q: The number of electrons that half fill a composite s-d band is ________.

Q: 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 ________.

Q: 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.

Q: Write a balanced chemical equation for obtaining iron metal by the reduction of hematite, Fe2O3, by hydrogen gas.

Q: Copper can be obtained from its copper(I) sulfide ore by roasting. What is the balanced equation for the roasting of copper(I) sulfide?

Q: The balanced chemical equation for the production of silver by roasting of its sulfide is ________.

Q: One source of scandium is kolbeckite, which is a dihydrated phosphate of scandium. What is the formula of kolbeckite?

Q: One source of titanium is illmenite, FeTiO3. Other ores containing titanium are geikielite, MgTiO3, and pyrophanite, MnTiO3. The oxidation states of iron and titanium in illmentite are ________ and ________, respectively.

Q: The principal source of chromium is chromite, FeCr2O4 in which chromium has an oxidation state of ________ and iron has an oxidation state of ________.

Q: Which one of the following is an electrical insulator?A) phosphorusB) platinumC) potassiumD) ruthenium

Q: Which element has the smallest energy band gap? A) B B) I C) K D) S

Q: Which one of the following metals is expected to have the highest melting point? A) La B) Nb C) Hg D) Pd

Q: Which substance is the best conductor of electricity? A) arsenic B) boron C) silver D) tellurium

Q: Which schematic best represents the electrical resistance versus temperature curve for a superconductor?A) AB) BC) CD) none of these

Q: Which picture (1)-(4) shows the electron populations when the silicon is doped with arsenic? A) picture (1) B) picture (2) C) picture (3) D) picture (4)

Q: Which picture (1)-(4) shows the electron populations when the silicon is doped with gallium? A) picture (1) B) picture (2) C) picture (3) D) picture (4)

Q: Which picture represents an n-type Si semiconductor? A) picture (A) B) picture (B) C) both picture (A) and picture (B) D) neither picture (A) nor picture (B)

Q: Which picture represents a p-type Si semiconductor? A) picture (A) B) picture (B) C) both picture (A) and picture (B) D) neither picture (A) nor picture (B)

Q: In this picture the valence band is given by letter(s) A) a. B) b. C) c. D) a and b.

Q: In this picture the conduction band is given by letter(s) A) a. B) b. C) c. D) a and b.

Q: In this picture the band gap is given by letter(s) A) a. B) b. C) c. D) a and b.

Q: Which picture corresponds to Cd? A) picture (1) B) picture (2) C) picture (3) D) picture (4)

Q: Which picture corresponds to Ag? A) picture (1) B) picture (2) C) picture (3) D) picture (4)

Q: Which picture corresponds to Mo? A) picture (1) B) picture (2) C) picture (3) D) picture (4)

Q: Which picture corresponds to Y? A) picture (1) B) picture (2) C) picture (3) D) picture (4)

Q: Which picture corresponds to Zn? A) picture (1) B) picture (2) C) picture (3) D) picture (4)

Q: Which picture corresponds to V? A) picture (1) B) picture (2) C) picture (3) D) picture (4)

Q: Which picture corresponds to Ti? A) picture (1) B) picture (2) C) picture (3) D) picture (4)

Q: Which picture corresponds to Sc? A) picture (1) B) picture (2) C) picture (3) D) picture (4)

Q: Which is the hardest metal? A) metal (1) B) metal (2) C) metal (3) D) metal (4)

Q: Which metal has the lowest melting point? A) metal (1) B) metal (2) C) metal (3) D) metal (4)

Q: Which metal has the highest melting point? A) metal (1) B) metal (2) C) metal (3) D) metal (4)

Q: Which of these materials has an electrical conductivity that remains constant with an increase in temperature? A) material (1) B) material (2) C) material (3) D) material (4)

Q: Which of these materials has an electrical conductivity that decreases with an increase in temperature? A) material (1) B) material (2) C) material (3) D) material (4)

Q: Which of these materials has an electrical conductivity that increases with an increase in temperature? A) materials (1) and (2) B) materials (1) and (4) C) materials (2) and (3) D) materials (3) and (4)

Q: Which of these materials has the lowest electrical conductivity? A) material (1) B) material (2) C) material (3) D) material (4)

Q: Which of these materials has the highest electrical conductivity? A) material (1) B) material (2) C) material (3) D) material (4)

Q: Which of these materials is a semiconductor? A) materials (1) and (2) B) materials (1) and (4) C) materials (2) and (3) D) materials (3) and (4)

Q: Which of these materials is a metal? A) material (1) B) material (2) C) material (3) D) material (4)

Q: Which of these materials is an insulator? A) material (1) B) material (2) C) material (3) D) material (4)

Q: Which diagram describes the molecular orbital picture for the species Na6? A) diagram (4) B) diagram (5) C) diagram (6) D) diagram (7)

Q: What diagram would describe the molecular orbital picture for the species Na4? A) diagram (1) B) diagram (2) C) diagram (3) D) diagram (4)

Q: Which of these elements is likely to be extracted from its ore by electrolysis? A) element A B) element B C) element C D) element D

Q: Which of these elements is likely to be extracted from its ore by chemical reduction of a metal oxide? A) element A B) element B C) element C D) element D

Q: Which of these elements is likely to be extracted from its ore by roasting of a metal sulfide? A) element A B) element B C) element C D) element D

Q: Which of these elements is likely to be found in nature as an oxide? A) element A B) element B C) element C D) element D

Q: Which of these elements is likely to be found in nature as a sulfide? A) element A B) element B C) element C D) element D

Q: Which of these elements is likely to be found in nature as a free metal? A) element A B) element B C) element C D) element D

Q: Which of these elements is likely to be found in nature as a carbonate? A) element A B) element B C) element C D) element D

Q: Relative to a bulk sample of gold, nanoparticles of gold have A) greater reactivity and higher melting point. B) greater reactivity and lower melting point. C) lower reactivity and higher melting point. D) lower reactivity and lower melting point.

Q: Silicon nitride/zirconia is a example of a A) ceramic-ceramic composite B) ceramic-metal composite C) ceramic-polymer composite D) superconductor

Q: What is a cermet? A) boron nitride/epoxy B) ceramic-metal composite C) ceramic-polymer composite D) silicon carbide/graphite

Q: Silica (SiO2) can be prepared from silicon ethoxide by the sol-gel process. Write a balanced equation for the hydrolysis of silicon ethoxide.A) SiCl4 + 4 HOCH2CH3 + 4 NH3 -> Si(OCH2CH3)4 + 4 NH4Cl (in benzene)B) Si(OCH2CH3)4 + 4 H2O -> Si(OH)4 + 4 HOCH2CH3C) Si(OCH2CH3)4 + 4 HOCH3 -> Si(OCH3)4 + 4 HOCH2CH3D) Si(OCH3)4 + 4 H2O -> Si(OH)4 + 4 HOCH3

Q: What is not part of the sol-gel process for the production of titania?A) TiCl4 + 4 HOCH2CH3 + 4 NH3 -> Ti(OCH2CH3)4 + 4 NH4Cl (in benzene)B) Ti(OCH2CH3)4 + 4 H2O -> Ti(OH)4 + 4 HOCH2CH3C) (HO)3-Ti-OH + HO-Ti-(OH)3 -> (HO)3-Ti-O-Ti(OH)3 + H2OD) 4 Ti(OH)4 + heat -> 2 Ti2O3 + 8 H2O + O2

Q: What is the sol-gel process? A) a series of chemical steps that involves the isolation of CuS and then roasting with oxygen B) a series of chemical steps that involves the isolation of SO3 and then treatment with H2SO4 C) a series of chemical steps that involves the synthesis of a metal oxide powder from a metal alkoxide D) a series of chemical steps that involves the thermal decomposition of fibers of polyacrylonitrile

Q: What is the coordination number of Si in SiC that has a diamond-like structure? A) 1 B) 2 C) 4 D) 6

Q: What is not generally considered to be a ceramic? A) indium, In B) silica, SiO2 C) silicon nitride, Si3N4 D) zirconia, ZiO2

Q: What is the name of the oxide ceramic BeO? A) beryllia B) beryllic C) beryllium ceramic D) beryllium oxide

Q: What substance has a rating of 10 on the Mohs hardness scale? A) alumina B) aluminum C) diamond D) talc

Q: Why are ceramics so much more brittle than metals? A) The bonding in ceramics has a very high degree of ionic bonding character. B) The bonding in ceramics has a very high degree of pi bonding character. C) The bonding in ceramics is highly nondirectional. D) The localized bonding in ceramics is highly directional.

Q: Sintering is A) a filtration process through a molecular sieve. B) the process of heating particles of a powder below the melting point so that they fuse together. C) the process of rapid cooling of a material to yield a superconducting mixture. D) the process of removing metals from ore by passing material through a magnetic field.