Refining of crude Metal Questions in English

(A) In the electrolytic refining of aluminum (Hoopes process),the cell consists of three layers of molten liquids of different densities.
The bottom layer is molten impure aluminum which acts as the anode.
The middle layer consists of molten fluorides of $Al, Ba,$ and $Na$.
The top layer is molten pure aluminum which acts as the cathode.
During electrolysis,$Al^{3+}$ ions from the middle layer are reduced at the cathode to form pure $Al$.

(C) Zone refining is based on the principle that impurities are more soluble in the melt than in the solid state of the metal.
As the heater moves,the pure metal crystallizes out of the melt and the impurities pass into the adjacent molten zone.
This method is particularly useful for producing semiconductors like $Si, Ge, Ga, B,$ and $In$ in a very high state of purity.

(D) The refining of iron is typically done by the process of oxidation of impurities in a Bessemer converter or an open-hearth furnace. Among the given options,the process of removing impurities by oxidation is the standard method for iron. However,in the context of metallurgical processes,iron is often refined by oxidation of impurities. Given the options,the most appropriate answer is $D$ (Cupellation is generally for silver,but in some contexts,oxidation-based refining is referred to as cupellation or oxidation refining).

(C) Electrolytic refining is used to obtain ultra-pure copper. After this process,the purity of copper is $99.99\%$,which is suitable for electrical applications.

(B) The $Van-Arkel$ method is used for refining metals like $Zr$ and $Ti$.
In this process,the crude metal is heated in an evacuated vessel with iodine to form a volatile metal iodide.
For example,$Zr + 2I_2 \rightarrow ZrI_4$.
This volatile metal iodide is then decomposed on a tungsten filament at a higher temperature to obtain pure metal.
Thus,the metal is converted into a volatile stable compound.

(D) Zone refining is a technique used to obtain metals and semiconductors in a state of high purity.
It is based on the principle that the impurities are more soluble in the melt than in the solid state of the substance.
This method is widely used for the purification of semiconductors like $Si$,$Ge$,and $Ga$.

(D) Zone refining is based on the principle that the impurities are more soluble in the molten state of the metal than in the solid state.
As the heater moves,the pure metal crystallizes out of the melt,while the impurities pass into the adjacent molten zone.

(A) The correct matches are as follows:
$(I)$ Van Arkel method is used for the refining of metals like $Ti$ and $Zr$. Thus,$(I) - a$.
$(II)$ Solvay process is the industrial process for the manufacture of sodium carbonate $(Na_2CO_3)$. Thus,$(II) - b$.
$(III)$ Cupellation is a refining process used to separate noble metals like silver from base metals. Thus,$(III) - d$.
$(IV)$ Poling is a process used for the refining of copper,where green wood poles are used to reduce copper oxide to copper. Thus,$(IV) - c$.
Therefore,the correct sequence is $I-a, II-b, III-d, IV-c$.

(C) Zone refining is a technique used to purify semiconductors and other materials.
It is based on the principle that impurities are more soluble in the molten state than in the solid state.
$Ge$ (Germanium),$Si$ (Silicon),and $Ga$ (Gallium) are typically purified using this method to obtain high-purity semiconductors.

(D) The refining of metals involves removing impurities to obtain pure metal.
$1$. Mond process is used for refining $Ni$.
$2$. Van Arkel method is used for refining $Zr$ and $Ti$.
$3$. Zone refining is used for producing semiconductors like $Si$ and $Ge$.
$4$. Amalgamation is a process used for the extraction of metals (like $Au$ or $Ag$) from their ores by forming an amalgam with mercury,not for the refining of impure metals.

(C) The Goldschmidt alumino-thermite process is used for the reduction of metal oxides like $Cr_2O_3$ using $Al$. This is correct.
The MacArthur-Forrest cyanide process is used for the extraction of $Ag$ or $Au$,not $Fe$. This is incorrect.
The Mond process is used for the refining of $Ni$ by forming $Ni(CO)_4$. This is correct.
The Van Arkel process is used for the refining of metals like $Zr$ or $Ti$,not $Au$. This is incorrect.
Therefore,the incorrect pairs are $(b)$ and $(d)$.

(B) $Zr$ and $Ti$ are purified by the van Arkel method.
$\underset{\text{Impure}}{Zr + 2I_2}$ $\xrightarrow{600\,^{\circ}C} ZrI_4$ $\xrightarrow{1800\,^{\circ}C} \underset{\text{Pure}}{Zr + 2I_2}$
This method is useful for removing all the oxygen and nitrogen present as impurities in certain metals like $Zr$ and $Ti$.

(D) The given reaction represents the Van Arkel method for the refining of metals like $Ti$ and $Zr$.
In this process,the crude metal is heated in an evacuated vessel with iodine to form a volatile metal iodide $(TiI_4)$.
The metal iodide is then decomposed by heating it over a tungsten filament at a higher temperature $(1700 \ K)$ to obtain the pure metal.
This method is specifically used to remove oxygen and nitrogen impurities from metals.

(B) Cupellation is the process used when the alloy of $Ag$ and $Pb$ is rich in $Ag$.
In this method,the impure metal is heated in a cupel (an oval-shaped crucible made of bone ash or cement).
$A$ blast of air is passed over the molten mass.
The $Pb$ impurities get oxidized to $PbO$ and are removed with the blast of air,leaving behind pure $Ag$.

(A) The purification of $Ni$ (Nickel) is carried out by the $Mond's$ process.
In this process,impure nickel is heated in a stream of carbon monoxide $(CO)$ at $330-350 \ K$ to form a volatile complex,nickel tetracarbonyl,$[Ni(CO)_4]$.
The reaction is: $Ni(s) + 4CO(g) \xrightarrow{330-350 \ K} [Ni(CO)_4](g)$.
This complex is then heated to a higher temperature $(450-470 \ K)$,causing it to decompose to give pure nickel.
The reaction is: $[Ni(CO)_4](g) \xrightarrow{450-470 \ K} Ni(s) + 4CO(g)$.

(D) In the electrolytic refining of silver,the impure silver acts as the anode and pure silver acts as the cathode.
Metals that are less reactive than silver $(Ag)$ do not dissolve in the electrolyte and settle down at the bottom of the anode as anode mud.
Since gold $(Au)$ is less reactive than silver,it remains in the anode mud.
Metals more reactive than silver,such as $Zn$ and $Cu$,dissolve into the electrolyte solution as ions.

(A) Poling is a metallurgical process used for the purification of copper $(Cu)$.
In this process,molten impure copper is stirred with green wooden poles.
The hydrocarbons from the wood reduce the cuprous oxide $(Cu_2O)$ impurity present in the copper to metallic copper $(Cu)$.

(D) Vapour phase refining is a process used for the purification of metals by converting them into a volatile compound and then decomposing it to obtain the pure metal.
$1$. $Ni$ is purified by the $Mond$ process,where it reacts with $CO$ to form $Ni(CO)_4$,which is then decomposed at high temperature.
$2$. $Ti$ and $Zr$ are purified by the $van$ $Arkel-de$ $Boer$ process,where they react with $I_2$ to form volatile iodides ($TiI_4$ and $ZrI_4$),which are then decomposed on a tungsten filament.
Therefore,all the given metals can be purified by vapour phase refining methods.

(D) The refining of nickel is carried out by the $Mond's$ process.
In this process,impure nickel is heated in a stream of carbon monoxide $(CO)$ at $330-350 \ K$ to form a volatile nickel tetracarbonyl complex,$Ni(CO)_4$.
The reaction is: $Ni(s) + 4CO(g) \xrightarrow{330-350 \ K} Ni(CO)_4(g)$.
This complex is then decomposed at a higher temperature $(450-470 \ K)$ to obtain pure nickel: $Ni(CO)_4(g) \xrightarrow{450-470 \ K} Ni(s) + 4CO(g)$.

(C) Cupellation is a refining process used to separate noble metals like $Ag$ and $Au$ from base metals like $Pb$,$Cu$,and $Zn$. In this process,the impure metal is heated in a cupel (a shallow porous vessel) in a blast of air,where base metals oxidize and are removed,leaving behind pure silver.

(C) Blister copper is obtained during the extraction of copper from copper matte.
It contains approximately $98\%$ pure copper and $2\%$ impurities.
The name 'blister' arises because of the evolution of $SO_2$ gas,which forms blisters on the surface of the solidified metal.

(B) The Mond process is used for the purification of nickel.
In this process,impure nickel is heated in a stream of carbon monoxide $(CO)$ at $330-350 \ K$ to form a volatile complex,nickel tetracarbonyl,$[Ni(CO)_4]$.
$Ni(s) + 4CO(g) \xrightarrow{330-350 \ K} [Ni(CO)_4](g)$
This complex is then subjected to higher temperatures $(450-470 \ K)$,which causes thermal decomposition to yield pure nickel metal.
$[Ni(CO)_4](g) \xrightarrow{450-470 \ K} Ni(s) + 4CO(g)$
Thus,the metal is obtained by thermal decomposition.

(C) In the electrorefining process of copper,the impure copper acts as the anode and pure copper as the cathode.
During electrolysis,more electropositive impurities like $Fe$,$Ni$,and $Zn$ dissolve into the electrolyte solution.
Noble metals like $Au$,$Ag$,and $Pt$ are less reactive and do not dissolve; they settle down at the bottom of the electrolytic cell below the anode,which is known as anode mud.

(C) The Mond process is used for the refining of nickel.
Nickel is heated with $CO$ at a lower temperature to form highly volatile nickel tetracarbonyl.
It is then decomposed to pure nickel at a higher temperature.
The reaction conditions are:
$Ni + 4CO$ $\xrightarrow{50^{\circ} C} Ni(CO)_4$ $\xrightarrow{230^{\circ} C} Ni + 4CO$
Thus,$T_1$ is $50^{\circ} C$ and $T_2$ is $230^{\circ} C$.

(B) Zone refining is a method used to obtain metals of high purity.
It is based on the principle that the impurities are more soluble in the molten state of the metal than in the solid state.
As the heater moves,the pure metal crystallizes out of the melt,while the impurities pass into the adjacent molten zone,effectively concentrating them at one end of the rod.

(D) Poling is a metallurgical process used to remove oxide impurities from molten metals.
It is specifically used for metals like $Cu$ (copper) and $Sn$ (tin) where the metal oxide is dissolved in the molten metal.
In this process,the molten metal is stirred with green wood poles.
The hydrocarbons from the wood reduce the metal oxide to the pure metal.

(A) Semiconductor materials like $Si$ and $Ge$ are usually purified by zone refining.
Zone refining is based on the principle of fractional crystallisation.
Due to the difference in the solubility of impurities in the molten and solid states of the metal,the impurities concentrate in the molten zone and are moved to one end,where they are finally removed.

(B) Electrorefining is a process used for the purification of metals like $Cu$,$Zn$,$Ag$,$Ni$,etc.
In this process,the impure metal is made the anode and a thin strip of pure metal is made the cathode.
Highly reactive metals like $Na$,$K$,$Ca$,and $Mg$ cannot be refined by this method because they are obtained by the electrolysis of their fused salts,not aqueous solutions,as they react vigorously with water.
Therefore,$Sodium$ cannot be refined using this method.

(B) The metal that forms a volatile compound is $Nickel$,and it is extracted by taking advantage of this property. This process is called vapour phase refining,in which the metal is converted into a volatile compound while the impurities remain unaffected.
The compound formed later decomposes upon heating to yield the pure metal.
In the case of $Nickel$,it is heated in a stream of carbon monoxide to form the volatile nickel carbonyl,$Ni(CO)_4$. This,upon thermal decomposition at a higher temperature $(450-470 \ K)$,yields pure $Nickel$.
$Ni_{(s)} + 4CO_{(g)}$ $\rightarrow Ni(CO)_{4(g)}$ $\rightarrow Ni_{(s)} + 4CO_{(g)}$
This refining process of $Ni$ is known as the $Mond$ process.

(A) Cupellation is a process used for the refining of noble metals like $Ag$ and $Au$.
In this process,the impure metal is heated in a cupel (a shallow porous dish) in a blast of air.
The impurities,which have a greater affinity for oxygen than the metal,get oxidised and are removed as slag or volatile oxides,while the noble metal remains unaffected due to its inert nature.

(B) Mercury has a low boiling point. Therefore,it can be purified by the process of distillation. In this process,mercury evaporates and is collected in pure form,while impurities remain behind.

(C) The $Van-Arkel$ process is a method used for the refining of metals like $Zr$ and $Ti$.
In this process,the crude metal is heated in an evacuated vessel with iodine to form a volatile metal iodide,such as $ZrI_4$.
The metal iodide is then decomposed on a tungsten filament at a higher temperature $(1800 \ K)$ to obtain pure metal.
Therefore,the $Van-Arkel$ process employs the thermal decomposition of volatile iodide compounds.

(D) $(i)$ Iron and copper are purified by Bessemerisation $(Q)$.
$(ii)$ Zirconium and Titanium are purified by the Van Arkel method $(R)$.
$(iii)$ Lead and Tin are purified by Liquation $(S)$.
$(iv)$ Copper and Tin are purified by Poling $(P)$.
Thus,the correct matching is $(i)-Q, (ii)-R, (iii)-S, (iv)-P$.

(D) During the electrolytic refining of silver,metals that are less reactive than silver do not dissolve in the electrolyte and settle at the bottom of the anode as anode mud.
Since $Au$ (gold) is less reactive than $Ag$ (silver),it remains as anode mud.
$\therefore (D)$ is the correct option.

(C) The Van-Arkel process is used for the refining of metals like $Ti$,$Zr$,$Hf$,and $B$ by forming volatile iodides.
The Mond's process is specifically used for the refining of $Ni$ (Nickel) by forming volatile nickel tetracarbonyl,$Ni(CO)_4$.
Therefore,the Van-Arkel process is used for $Ti$ (or $Zr$) and the Mond's process is used for $Ni$.

(C) The given equation represents the $Van-Arkel$ process.
This method is used for the refining of metals like $Ti$ and $Zr$.
In this process,the metal is converted into a volatile iodide compound,which is then decomposed at a higher temperature to obtain the pure metal.

(C) The $Van \ Arkel$ method is used for the refining of metals like $Ti, Zr,$ and $Hf$ by forming volatile iodides.
Option $C$ represents the thermal decomposition of silver carbonate,which is not a $Van \ Arkel$ process.
Therefore,option $C$ is the incorrect representation.

(D) The process used for the refining of $Ni$ is known as the $Mond$ process.
In this process,impure nickel is heated in a stream of carbon monoxide $(CO)$ at $330-350 \ K$ to form a volatile complex,nickel tetracarbonyl,$Ni(CO)_4$.
This complex is then decomposed at a higher temperature $(450-470 \ K)$ to obtain pure nickel.
The chemical reactions are:
$Ni(s) + 4CO(g) \rightarrow Ni(CO)_4(g)$
$Ni(CO)_4(g) \rightarrow Ni(s) + 4CO(g)$

(D) The Mond process is used for the refining of nickel $(Ni)$ based on the principle of formation of a volatile carbonyl complex.
The chemical reactions involved are:
$\mathop {Ni}\limits_{\text{impure}} + 4CO_{(g)} \xrightarrow{330-350 \ K} Ni(CO)_{4(g)}$
$Ni(CO)_{4(g)} \xrightarrow{450-470 \ K} \mathop {Ni_{(s)}}\limits_{\text{pure}} + 4CO_{(g)}$

(D) The correct matches are as follows:
$I$. Liquation is used for metals with low melting points like $Sn$.
$II$. Zone refining is used for semiconductors like $Ga$.
$III$. Mond process is specifically used for the refining of $Ni$.
$IV$. Van Arkel method is used for refining metals like $Zr$ and $Ti$.
Therefore,the correct matching is $I-c, II-d, III-b, IV-a$.

(A) The poling process is primarily used in the metallurgy of copper.
It involves stirring the molten crude copper with green wooden poles.
The hydrocarbons from the wood reduce the copper$(I)$ oxide $(Cu_2O)$ present as an impurity in the copper to metallic copper $(Cu)$.
Therefore,it is used for the removal of $Cu_2O$ from $Cu$.

(D) Cupellation is a refining process used for metals that have a low affinity for oxygen,such as silver. In this process,the impure metal is heated in a cupel (a shallow porous vessel) in the presence of air. The impurities (like lead) oxidize to form oxides,while the noble metal remains in its metallic state.

(D) The $Parkes$ process is a pyrometallurgical industrial process for removing silver from lead during the production of bullion.
It is an example of liquid-liquid extraction.
The process takes advantage of two liquid-state properties of zinc.
The first is that zinc is immiscible with lead,and the other is that silver is $3000$ times more soluble in zinc than it is in lead.
When zinc is added to liquid lead that contains silver as a contaminant,the silver preferentially migrates into the zinc.
Because the zinc is immiscible in the lead,it remains in a separate layer and is easily removed.

(C) All processes are used in $Aluminium$ metallurgy,but the $Hoopes$ process is an electrolytic refining process used to obtain $Aluminium$ metal of very high purity $(99.99\%)$.
$1$. The $Bayer$ process is the principal industrial means of refining bauxite to produce alumina $(Al_2O_3)$.
$2$. The $Hall-Héroult$ process is the major industrial process for smelting $Aluminium$ from alumina.
$3$. $Serpeck's$ process is used for the purification of bauxite ore containing silica $(SiO_2)$ as the main impurity.

(D) Spiegleisen is an alloy of $Mn$,$Fe$,and $C$.
Dow's process uses $Ca(OH)_2$ to precipitate $Mg(OH)_2$ from sea water.
Parke's process is used for the desilverization of lead,involving $Ag$.
Liquation is used for metals with low melting points like $Sn$ (tin),whereas spelter (impure $Zn$) is purified by distillation or electrolytic refining.
Thus,the option $D$ is not correctly matched.

(A) Cupellation is a process used for the refining of silver and gold,where base metals like lead are removed by oxidation. It is not used for the refining of tin. Tin is typically refined by liquation,poling,or electrorefining.

(D) The $Mond$ process is specifically used for the refining of nickel $(Ni)$.
In this process,impure nickel is heated in a stream of carbon monoxide $(CO)$ to form volatile nickel tetracarbonyl,$Ni(CO)_4$.
This volatile complex is then decomposed at a higher temperature to obtain pure nickel.
Therefore,the pairing of $Mond$ process with lead is incorrect.

(A) Hoope's process is used for the electrolytic refining of impure aluminium to obtain high-purity aluminium. The other processes,such as Hall's,Serpeck's,and Baeyer's,are methods used for the concentration or purification of bauxite ore to obtain pure alumina $(Al_2O_3)$.

(A) The Poling process is used for the purification of metals that contain their own oxides as impurities.
In this process,the molten metal is stirred with green wood poles.
The hydrocarbons released from the green wood reduce the metal oxide impurities back to the pure metal.
For example,impure $Cu$ (containing $Cu_2O$) and $Sn$ (containing $SnO_2$) are purified using this method.

(B) Zone refining is based on the principle that impurities are more soluble in the molten state of the metal than in the solid state.
As the heater moves along the metal rod,the impurities dissolve into the molten zone.
Consequently,the molten zone becomes enriched with impurities,meaning it contains more impurity than the original solid metal.
As the molten zone moves forward,the pure metal crystallizes out,leaving the impurities behind in the molten zone.