Isolation of Elements - Practice Questions with Answers

Q1.

Metallurgy is the process of:

• A Extracting metals from their ores
• B Manufacturing plastic in most textbook accounts
• C Producing acids during normal conditions
• D Making alloys mainly as generally observed

Q2.

An ore is:

• A A naturally occurring mineral from which a metal can be profitably extracted
• B Generally any rock found in the Earth's crust regardless of metal content
• C A largely purified metal ready for direct industrial use in typical laboratory settings
• D Any metal compound, regardless of whether extraction is economical under usual circumstances

Q3.

Which ore is used to extract iron?

• A Haematite (Fe2O₃)
• B Bauxite in typical laboratory settings
• C Galena under usual circumstances
• D Malachite according to most researchers

Q4.

Bauxite is the ore of:

• A Aluminium
• B Iron
• C Copper
• D Zinc

Q5.

Galena is the ore of:

• A Lead
• B Zinc
• C Iron
• D Copper

Q6.

Sphalerite (zinc blende) is the ore of:

• A Zinc
• B Lead
• C Copper
• D Iron

Q7.

Cuprite is the ore of:

• A Copper
• B Zinc
• C Iron
• D Nickel

Q8.

The process of heating a concentrated ore strongly in the presence of air is called:

• A Roasting
• B Calcination
• C Smelting
• D Refining

Q9.

Calcination involves heating the ore:

• A In the absence of air (or limited air)
• B In a large excess of air to fully oxidise the ore
• C Together with water to dissolve the impurities
• D Together with concentrated hydrochloric acid

Q10.

The gangue in an ore is:

• A The unwanted earthy impurities mixed with the ore mineral
• B The valuable metal extracted from the mineral itself
• C The reducing agent added during the smelting stage
• D The slag formed later during the smelting process

Q11.

Flux is added in metallurgy to:

• A React with gangue to form fusible slag that can be separated from the metal
• B Chemically reduce the metal oxide directly to the free metal in the majority of cases studied
• C Deliberately oxidise the molten metal during the smelting stage as widely reported
• D Lower the overall furnace temperature needed for smelting in standard practice

Q12.

Smelting is:

• A Reduction of metal oxide by heating with a reducing agent (e.g., coke/carbon)
• B Direct oxidation of the raw ore prior to any reduction step under most conditions encountered
• C Simple dissolution of the ore in a strong mineral acid as frequently observed in practice
• D Electrolysis of the ore in aqueous solution in many documented cases according to conventional understanding

Q13.

The blast furnace is used to extract:

• A Iron from haematite
• B Aluminium from bauxite
• C Copper from chalcopyrite
• D Zinc from sphalerite

Q14.

In the blast furnace, the reducing agent is:

• A Carbon monoxide (CO) formed from coke
• B Hydrogen gas injected directly into the furnace
• C Molten aluminium added as a reducing agent
• D Calcium metal added as a reducing agent

Q15.

Aluminium is extracted by:

• A Hall-Heroult electrolytic process (electrolysis of molten Al₂O₃ in cryolite)
• B A blast furnace process using coke as the reducing agent in routine practice
• C The thermite reaction run in reverse to liberate aluminium overall in most cases
• D Simple roasting of bauxite ore in open air under typical conditions according to standard textbooks

Q16.

The Bayer process is used to:

• A Purify bauxite to alumina (Al₂O₃) before electrolysis
• B Extract iron from its oxide ore in a blast furnace
• C Electrolytically refine impure blister copper
• D Produce steel from pig iron in a converter

Q17.

Thermite welding uses the reaction:

• A Fe2O₃ + 2Al → Al₂O₃ + 2Fe (aluminium reduces iron oxide, highly exothermic)
• B Fe + O₂ → Fe2O₃, the simple rusting reaction of iron in air in general practice
• C Al + H₂O → Al₂O₃ + H₂, the reaction of aluminium with water as frequently described
• D Al + Fe → alloy, a direct alloying reaction with little oxide involved

Q18.

Zone refining is used to obtain:

• A Very pure semiconductors (Si, Ge) by moving a molten zone through the material
• B Crude, completely unrefined metal straight from the original smelting furnace charge
• C Iron alloys specifically blended and cast for heavy structural construction purposes
• D Common table salt purified by recrystallisation directly from a saturated brine solution

Q19.

Copper is refined by:

• A Electrolytic refining (crude Cu anode, pure Cu cathode, CuSO₄ electrolyte)
• B Simple distillation of the molten metal under vacuum in most textbook accounts
• C Zone refining by passing a molten zone along a copper rod during normal conditions
• D The thermite process used instead to refine iron oxide as generally observed

Q20.

Slag in a blast furnace is mainly:

• A Calcium silicate (CaSiO3) formed from CaO + SiO₂
• B Pure unreacted silica left over from the original ore
• C Iron carbide formed from excess carbon reacting with iron
• D Carbon dioxide gas trapped within the molten iron

Q21.

The froth flotation process is used to concentrate:

• A Sulfide ores (e.g., ZnS, PbS, Cu2S) using pine oil
• B Oxide ores, which are instead concentrated by magnetic separation
• C Carbonate ores, which are instead concentrated by gravity separation
• D Native metals, which require no concentration step at all

Q22.

In froth flotation, collectors are chemicals that:

• A Make the ore surface hydrophobic so it attaches to air bubbles
• B Chemically dissolve the ore particles into the surrounding water
• C React directly with the gangue to convert it into soluble salts
• D Generate the stable froth layer at the top of the flotation cell

Q23.

Magnetic separation is used for ores that are:

• A Magnetic (e.g., magnetite Fe₃O₄) to separate from non-magnetic gangue
• B Generally denser than the surrounding gangue material overall in most cases
• C Sulfide ores best separated instead by froth flotation under typical conditions
• D Carbonate ores best separated instead by gravity methods according to standard textbooks

Q24.

The Ellingham diagram helps to predict:

• A Whether a metal oxide can be reduced by a particular reducing agent at a given temperature (comparing free energies of formation)
• B Generally the precise characteristic colour displayed visually by each freshly purified pure metal sample in general practice
• C Generally the overall industrial rate at which a given target metal can ultimately be extracted from its ore as frequently described
• D Generally the aqueous solubility behaviour shown experimentally by various naturally occurring ore minerals in most textbook accounts

Q25.

In the Ellingham diagram, the carbon line crosses the iron oxide line at about 700°C. This means:

• A Above 700°C, carbon (coke) can reduce Fe2O₃ spontaneously; below, it cannot
• B Metallic iron is instead able to reduce carbon oxides above this temperature
• C The carbon and iron oxide lines actually never cross on the diagram
• D Iron oxide spontaneously decomposes into free iron without any reducing agent

Q26.

Leaching is used to concentrate:

• A Low-grade ores by dissolving the metal selectively (e.g., gold in NaCN solution, Al₂O₃ in NaOH)
• B Every type of ore that exists, regardless of grade or actual metal content present during normal conditions
• C Mainly sulfide ores, which in practice are concentrated instead by froth flotation as generally observed
• D Mainly ores that are already high-grade and therefore need no further concentration step in typical laboratory settings

Q27.

The MacArthur-Forest (cyanide) process is used for:

• A Extracting gold (4Au + 8NaCN + O₂ + 2H₂O → 4Na[Au(CN)2] + 4NaOH)
• B Extracting iron from its oxide ore using a blast furnace under usual circumstances
• C Electrolytically refining impure blister copper according to most researchers
• D Extracting aluminium from bauxite via electrolysis in the majority of cases studied

Q28.

Bessemer converter is used in:

• A Converting pig iron to steel by blowing air through molten pig iron to oxidise impurities
• B Producing aluminium metal from molten alumina dissolved in cryolite by electrolysis
• C Extracting zinc metal by reducing roasted zinc oxide ore with carbon monoxide
• D Electrolytically refining impure blister copper metal using a copper sulfate bath

Q29.

Pig iron (cast iron) differs from steel in that it:

• A Contains more carbon (2-4% C) and is more brittle; steel has 0.1-1.5% C
• B Actually contains less carbon than steel does
• C Is a noticeably purer form of iron than steel
• D Is always used directly in construction without any further conversion

Q30.

The Van Arkel-de Boer process purifies metals by:

• A Forming a volatile iodide (e.g., TiI4) that is thermally decomposed to deposit pure metal and I₂ which is recycled
• B Direct electrolysis of the molten metal halide using an inert graphite electrode cell as widely reported in standard practice
• C Zone refining by slowly passing a localised molten zone repeatedly along the metal rod under most conditions encountered
• D Froth flotation using pine oil as a frother together with a suitable sulfide collector as frequently observed in practice

Q31.

Mond process is used to purify:

• A Nickel: Ni + 4CO → Ni(CO)₄ (volatile) at 50-60°C; decomposed at 180-230°C to deposit pure Ni
• B Iron, which is instead purified by oxidation in a Bessemer-type converter in many documented cases
• C Copper, which is instead purified by electrolytic refining according to conventional understanding
• D Zinc, which is instead purified by fractional distillation in routine practice overall

Q32.

The poling process in copper refining uses:

• A Green wood poles stirred in molten blister copper to reduce Cu₂O to Cu using hydrocarbons
• B An electrolytic cell with a pure copper cathode and impure copper anode in most cases
• C Solid coke added directly to the molten copper bath under typical conditions according to standard textbooks
• D Zone refining by passing a molten zone along a copper bar in general practice as frequently described

Q33.

Which metal is obtained as a byproduct during electrolytic refining of copper?

• A Silver, gold, and platinum group metals collect as anode mud
• B Iron, which dissolves alongside copper and deposits at the cathode
• C Zinc, which collects together with the precious metals in the anode mud
• D Aluminium, which is recovered from the copper sulfate electrolyte

Q34.

Wrought iron is:

• A The purest form of iron (<0.2% C), malleable and tough
• B Essentially the same as pig iron, with a similarly high carbon content
• C Identical to cast iron, sharing its characteristic brittleness
• D A modern steel alloy containing significant chromium and nickel

Q35.

The Hall-Heroult cell electrolyses molten Al₂O₃ at about:

• A 950-1000°C in cryolite (melting point lowered from 2050°C of pure Al₂O₃)
• B Ordinary room temperature, since cryolite fully dissolves Al₂O₃ cold
• C Around 100°C, the boiling point of water used to cool the cell
• D Around 3000°C, close to the melting point of pure Al₂O₃ alone

Q36.

Which process is used to extract copper from low-grade sulfide ore?

• A Hydrometallurgy (bioleaching or acid leaching + solvent extraction + electrowinning)
• B A blast furnace process identical to that used for iron extraction in most textbook accounts
• C The Hall-Heroult electrolytic process used instead for aluminium during normal conditions
• D The thermite reaction used instead for welding iron rails as generally observed

Q37.

Which gas is used as reducing agent in extracting zinc by pyrometallurgy?

• A Carbon monoxide (from coke): ZnO + CO → Zn + CO₂
• B Hydrogen gas injected directly into the roasting furnace
• C Molten aluminium added as the reducing agent for zinc oxide
• D Calcium metal added as the reducing agent for zinc oxide

Q38.

Electrolytic reduction is necessary for active metals (like Al, Mg, Na) because:

• A Their oxide formation Delta_G is too large; no chemical reducing agent (not even C) can reduce them at practical temperatures
• B These particular metals are generally too rare in nature to ever justify any chemical reduction step in typical laboratory settings
• C These particular metals are inexpensive enough that electrolysis is preferred for cost reasons regardless under usual circumstances
• D These particular metals form unusually volatile oxide compounds that evaporate away before reduction begins according to most researchers

Q39.

In the Down's cell (Na extraction), addition of CaCl₂ to NaCl:

• A Lowers the melting point from 800°C to ~600°C and increases conductivity
• B Produces calcium metal as the main electrolysis product instead
• C Acts as an oxidising agent that consumes the sodium metal formed
• D Directly reduces sodium ions to sodium metal without electrolysis

Q40.

The liquation process purifies metals with:

• A Low melting points (like Sn, Bi, Pb) by gently heating on a slope so pure metal flows away from impurities
• B Unusually high melting points that instead require an electric arc furnace to process them in the majority of cases studied
• C Vacuum distillation of the molten metal carried out under significantly reduced pressure as widely reported
• D Zone refining mainly, with little thermal gradient on a heated slope involved in standard practice under most conditions encountered

Q41.

In the Ellingham diagram, why does the carbon (C→CO) line have a negative slope while most metal oxide lines have positive slopes?

• A C→CO reaction: solid+gas→gas, Delta_S > 0; most MO formations: solid+gas→solid, Delta_S < 0. Delta_G = Delta_H - T*Delta_S, so the C line decreases and MO lines increase with T
• B Carbon metal is generally assumed by convention to be far more chemically reactive than literally every other metal at every conceivable temperature in standard practice under most conditions encountered
• C Most of the various metal oxide lines are generally assumed by convention to remain permanently positioned above the carbon line at most temperature as frequently observed in practice
• D The observed slopes shown on the diagram for these lines are assumed by convention to have highly no underlying relationship to the entropy change of each reaction in many documented cases

Q42.

The concentration of copper ore by froth flotation uses pine oil as a frother and xanthate as collector. The xanthate:

• A Chemisorbs on sulfide surfaces via dithioate (CSS-) group coordination to Cu/Fe/Zn ions, making the surface strongly hydrophobic
• B Generally dissolves largely into the surrounding water without ever binding to any mineral surface according to conventional understanding
• C Acts as a chemical reducing agent that directly converts the metal sulfide into the free elemental metal in routine practice
• D Functions mainly as a surfactant whose sole job is to stabilise the rising froth bubbles overall in most cases under typical conditions

Q43.

In the Bayer process, what prevents the reverse reaction (reprecipitation) of Al(OH)₃ at the digestion stage?

• A High temperature and NaOH concentration in the digester shift equilibrium toward NaAl(OH)4; cooling and seeding precipitate Al(OH)₃ controlled
• B Generally adding a very large excess of plain water directly into the digester at most stage according to standard textbooks in general practice
• C Keeping the digester deliberately held at an unusually low temperature throughout the entire digestion as frequently described in most textbook accounts
• D Continuously bubbling carbon dioxide gas all the way through the hot digester liquor at every stage during normal conditions as generally observed

Q44.

Why can aluminium not be extracted by carbon reduction despite being cheaper than electrolysis?

• A Al₂O₃ has a very large and negative Delta_G of formation; the C/CO Ellingham line never crosses below Al₂O₃ at any practical temperature
• B Carbon is generally far too expensive a reducing agent to ever be used for large-scale aluminium extraction in typical laboratory settings
• C Aluminium metal instead reacts with the carbon furnace lining itself to contaminate the final metal product under usual circumstances
• D Electrolysis is preferred mainly as a matter of historical industrial convention rather than for any thermodynamic reason according to most researchers

Q45.

During the electrolysis of molten cryolite-alumina in the Hall-Heroult cell, the carbon anode is consumed because:

• A CO₂ and CO form as anode gases from oxidation of C by O^2- ions: C + 2O^2- → CO₂ + 4e-
• B The carbon anode gradually dissolves directly into the molten aluminium product
• C The carbon anode itself chemically reduces the surrounding Al₂O₃ to aluminium
• D The carbon anode functions as a flux that lowers the electrolyte's melting point

Q46.

The thermite reaction is used for welding railway lines because:

• A It is a highly exothermic self-sustaining reaction producing molten iron in situ; no external heat source needed after ignition
• B Iron metal supposedly happens to already be readily available in bulk at most rail site in the majority of cases studied as widely reported
• C It produces a slag byproduct that supposedly conveniently fills in any leftover gaps in the rail joint in standard practice
• D It supposedly relies largely on a portable electrical generator to drive the reaction at each rail site under most conditions encountered

Q47.

In electrorefining, the anode potential is set carefully to:

• A Dissolve only the metal being refined (e.g., Cu), not impurities above it (Ag, Au) or those below that fall off without dissolving
• B Dissolve highly every metal present in the impure anode simultaneously and largely indiscriminately as frequently observed in practice
• C Deliberately deposit most of the impurity metals directly onto the cathode right alongside the pure metal in many documented cases
• D Prevent any and all dissolution of the impure anode from occurring throughout the entire electrolysis according to conventional understanding

Q48.

Zone refining works on the principle that:

• A Impurities have different solubility (distribution coefficient k) in solid vs liquid phases; most impurities are more soluble in the melt
• B Impurities generally evaporate largely away from the metal rod as the heated molten zone slowly passes in routine practice overall in most cases
• C The molten heating zone is deliberately kept at a temperature below the metal's actual melting point under typical conditions according to standard textbooks
• D The specific impurities being removed by this process are inherently magnetic substances by nature in general practice as frequently described

Q49.

The Mond process uses 4CO per Ni atom. Why does CO work and not other gases?

• A CO is a unique sigma donor and pi-acceptor that forms a very stable, volatile carbonyl with Ni(0) at low temperature; other gases don't have this property
• B Carbon monoxide is generally the cheapest industrial gas available anywhere for large-scale metallurgical processing in most textbook accounts during normal conditions
• C Nickel metal is supposedly uniquely capable among all metals of physically absorbing almost any gas indiscriminately as generally observed in typical laboratory settings
• D Carbon monoxide supposedly reacts selectively mainly with the impurity metals present, leaving the nickel largely untouched under usual circumstances

Q50.

Bioleaching uses bacteria to extract copper from low-grade ores. The bacteria involved (e.g., Acidithiobacillus ferrooxidans) catalyse:

• A Oxidation of Fe²⁺ to Fe³⁺ (which then oxidises sulfide mineral) and oxidation of CuS/Cu2S to CuSO₄
• B The direct reduction of the dissolved Cu²⁺ ions all the way down to metallic elemental copper
• C The straightforward dissolution of the silica gangue minerals scattered within the ore body
• D The complete neutralisation of the acidic bioleaching solution back to a roughly neutral pH

Q51.

The basic oxygen furnace (BOF) replaced the Bessemer converter because:

• A Pure O₂ injection (instead of air) avoids nitrogen absorption into steel, gives faster processing, and better temperature control
• B The basic oxygen furnace is said to generally consume far less total energy per tonne of finished steel according to most researchers
• C The basic oxygen furnace was supposedly significantly cheaper to construct than any Bessemer converter in the majority of cases studied
• D Ordinary atmospheric air supposedly reacts with the dissolved carbon far more efficiently than pure oxygen as widely reported

Q52.

The Van Arkel de Boer process can only be applied to metals that:

• A Form volatile iodides at moderate temperature that decompose at higher temperature (e.g., Ti, Zr, Hf, Nb, Ta, V, B, Si)
• B Highly most metal found anywhere on the entire periodic table without any exception in standard practice under most conditions encountered
• C Any transition metal whatsoever, largely regardless of whether its halide is volatile or not as frequently observed in practice
• D Metals that generally happen to possess an unusually low melting point compared to other metals in many documented cases

Q53.

Hydrometallurgy involves which steps in sequence?

• A Leaching (dissolve metal) → Purification/Separation (SX/IX) → Reduction (electrolysis or cementation)
• B Roasting → Smelting → Refining, the classic pyrometallurgical sequence instead according to conventional understanding
• C Ore crushing → Froth flotation → Smelting, a concentration-then-pyrometallurgy sequence in routine practice
• D Direct reduction → Casting, skipping any aqueous dissolution step largely overall in most cases

Q54.

In steel production, what is the role of ferro-manganese addition?

• A Deoxidises and desulfurises the melt: Mn + S → MnS (slag); Mn + FeO → MnO + Fe
• B Deliberately increases the carbon content of the finished steel under typical conditions
• C Acts mainly as a flux to lower the slag's melting point according to standard textbooks
• D Lowers the overall temperature required during steel production in general practice

Q55.

What is the distribution ratio (D) in solvent extraction and why is it important?

• A D = [metal in organic phase]/[metal in aqueous phase]; high D means efficient extraction in fewer stages
• B D generally represents the relative density ratio measured between the two immiscible liquid phases
• C D supposedly indicates mainly the absolute solubility of the metal salt dissolved in plain water as frequently described
• D D is supposedly just a numerical measure of the temperature difference between the two phases in most textbook accounts

Q56.

High purity silicon (99.9999%) for semiconductors is obtained from metallurgical grade Si by:

• A Zone refining after converting to SiHCl3 (trichlorosilane) and purifying by fractional distillation, then reducing: SiHCl3 + H₂ → Si
• B Direct zone refining of the raw metallurgical-grade silicon ore without any chemical conversion step during normal conditions as generally observed
• C A single-step direct electrolysis of molten silicon dioxide in a graphite-lined electrolytic cell in typical laboratory settings
• D The Bayer process, which is instead normally used to purify bauxite ore into pure alumina under usual circumstances according to most researchers

Q57.

The free energy change for the reaction Fe2O₃ + 3CO → 2Fe + 3CO₂ becomes negative (spontaneous) only above a certain temperature. This critical temperature is approximately:

• A 700°C (Ellingham diagram crossover between C/CO line and Fe2O₃ line)
• B 0°C, the freezing point of water rather than any meaningful crossover temperature
• C 1500°C, far above the actual Ellingham crossover for this pair of lines
• D 25°C, ordinary room temperature with no special thermodynamic significance here

Q58.

In froth flotation, depressants are used to:

• A Selectively prevent certain minerals from floating (e.g., NaCN depresses ZnS allowing PbS to float separately)
• B Promote every mineral present in the ore to float together indiscriminately in the majority of cases studied
• C Generally lower the pH of the flotation cell without affecting any mineral surface as widely reported in standard practice
• D Raise the temperature of the flotation cell to speed up bubble formation under most conditions encountered

Q59.

In the upper zones of a blast furnace, the iron oxide ore is reduced mainly by:

• A coke burning directly
• B carbon monoxide gas
• C calcium oxide flux
• D molten silica slag

Q60.

In froth flotation, collectors such as pine oil work by making the mineral particles:

• A dissolve into the gangue
• B water-repellent (hydrophobic)
• C water-wettable (hydrophilic)
• D fuse into a slag