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Exam 21: Metallurgy and the Chemistry of Metals

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Question 21

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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.

F) C) and D)
G) A) and E)

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Question 22

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

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

F) B) and D)
G) A) and D)

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Question 23

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Which of the following diagrams represents a semiconductor

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

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

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

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

The principal reducing agent in a blast furnace is

What is the total number of moles (n) of electrons exchanged between the oxidizing agent and the reducing agent in the reaction below to obtain vanadium metal V₂O₅(s) + 5Ca(l) $\rarr$ 2V(l) + 5CaO(s)

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

Cryolite, Na₃AlF₆, is mixed with alumina prior to electrolysis in the production of Al because it acts a solute.

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

A naturally occurring substance with a range of chemical composition is

What effect does increasing temperature have on the conductivities of semiconductors

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

Which one of these elements has seawater as its commercial source

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

Aluminum hydroxide, Al(OH) ₃, is

Volatile impurities are removed from ores by means of

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