Refining of crude Metal Questions in English

(A) Hoop's process is an electrolytic refining method used for the purification of $Al$ (Aluminum) to obtain high purity metal.
$A$. Hoop's process $\Rightarrow$ Purification of $Al$.
$B$. Hall-Heroult process $\Rightarrow$ Electrolytic reduction of $Al_2O_3$.
$C$. Baeyer's and Serpeck's process $\Rightarrow$ Concentration of Bauxite ore.

(D) Purification of aluminium by electrolytic refining is called Hoop's process.
By this method,$99.9\%$ pure aluminium metal is obtained.
The cell used in this method consists of three layers.
In the cell,pure $Al$ acts as the cathode,while the anode is made of impure $Al$.

(C) In the Hoope's process,the electrolytic cell consists of three liquid layers of different densities.
$1$. The bottom layer consists of impure aluminium (anode).
$2$. The middle layer consists of a fused mixture of fluorides (electrolyte).
$3$. The top layer consists of pure molten aluminium (cathode).
These layers remain separated during electrolysis because they have different densities,which prevents them from mixing.

(C) In the electrolytic refining of aluminium (Hoopes' process),the cell consists of three layers of fused electrolytes with different densities:
$1$. The bottom layer is the anode,which consists of impure aluminium alloyed with copper $(Cu)$ to increase its density.
$2$. The middle layer consists of a mixture of fluorides (cryolite $Na_3AlF_6$ and barium fluoride $BaF_2$) which acts as the electrolyte.
$3$. The upper layer is the cathode,which consists of pure molten aluminium.
Therefore,the correct arrangement is: Bottom layer (Anode of $Al$ and $Cu$ alloy),Middle layer (Cryolite and barium fluoride),Upper layer (Cathode of pure $Al$).

(D) In the process of electrolytic refining of metals,the impure metal is always made the anode,and a thin strip of pure metal is made the cathode.
Therefore,for the purification of copper,the pure copper strip acts as the cathode and the impure copper sample acts as the anode.
Thus,the correct choice is $D$.

(D) Pure metals generally have higher electrical and thermal conductivity compared to their alloys because the presence of foreign atoms in an alloy disrupts the regular crystal lattice,which increases scattering of electrons and phonons. Therefore,$(d)$ is the correct property that makes pure metals more useful in specific applications.

(C) During the electrolytic refining of copper,the impurities that are less reactive than copper,such as $Ag$ (silver) and $Au$ (gold),do not dissolve in the electrolyte.
Instead,they settle down at the bottom of the anode as 'anode mud'.

(B) The process described is the $Mond$ process,which is used for the refining of $Nickel$.
In this process,impure $Nickel$ is heated in a stream of carbon monoxide $(CO)$ to form a volatile complex,nickel tetracarbonyl:
$Ni + 4CO \rightarrow [Ni(CO)_4]$
This volatile complex is then decomposed at higher temperatures to obtain pure $Nickel$.

(D) The process of refining blister copper using green logs of wood is known as $poling$.
Green logs of wood release hydrocarbon gases (like $CH_4$) upon heating.
These gases reduce the cuprous oxide $(Cu_2O)$ impurities present in the blister copper back to metallic copper $(Cu)$.
The reaction is: $3Cu_2O + CH_4 \to 6Cu + 2H_2O + CO$.

(C) Electrolytic refining is typically used for metals like $Cu$,$Ag$,$Zn$,etc.,where the metal is deposited from an aqueous solution of its salt.
However,$Al$ (Aluminium) cannot be refined by this method because $Al$ is highly reactive and its aqueous salts undergo electrolysis to produce $H_2$ gas at the cathode instead of $Al$ metal.
$Al$ is refined by the Hoopes process,which uses a molten electrolyte,not an aqueous solution.

(C) The given reaction represents the $Van \ Arkel$ method.
This method is specifically used for the refining of metals like $Ti$ and $Zr$.
In this process,the crude metal is converted into a volatile compound,which is then decomposed to obtain the pure metal.

(B) The cupellation process is a refining method used for the purification of noble metals like $Silver$ $(Ag)$ from base metal impurities like $Lead$ $(Pb)$.
In this process,the impure metal is heated in a cupel (a shallow porous vessel) in a blast of air.
The base metal impurities oxidize to form volatile oxides (e.g.,$PbO$),which are either absorbed by the cupel or blown away,leaving behind the pure noble metal.

(B) In the process of electrolytic refining,the impure metal is made the $Anode$ and a thin strip of pure metal is made the $Cathode$.
During electrolysis,the impure metal from the $Anode$ dissolves into the electrolyte,and an equivalent amount of pure metal from the electrolyte deposits on the $Cathode$.

(A) The Van Arkel method is used for refining metals like $Ti$ and $Zr$.
In this process,the crude metal is heated in an evacuated vessel with iodine to form a volatile stable compound.
For example: $Ti + 2I_2 \xrightarrow{500 \ K} TiI_4 \text{ (Volatile stable compound)}$.
This volatile compound is then decomposed on a tungsten filament at a higher temperature to obtain the pure metal: $TiI_4 \xrightarrow{1700 \ K} Ti + 2I_2 \text{ (Pure metal)}$.

(C) Zone refining is employed for preparing extremely pure metals.
It is based on the principle that when a molten solution of the impure metal is allowed to cool,the pure metal crystallises out while the impurities remain in the melt.
Example: Semiconductors like $Si$,$Ge$,and $Ga$ are purified by this method.

(B) Poling is a process used for the purification of metals that contain their own oxides as impurities.
For example,$Cu_2O$ in $Cu$ (blister copper) and $SnO_2$ in $Sn$ are removed by this method.

(C) . Cupellation: When silver contains lead as an impurity,the mixture is heated in a cupel (a shallow porous dish) in a blast of air. Lead is oxidized to lead$(II)$ oxide $(PbO)$,which is either absorbed by the cupel or blown away,leaving behind pure silver.

(B) Electrolytic refining is a process of purifying metals where an impure metal block acts as the anode and a thin strip of pure metal acts as the cathode. $A$ solution of a soluble salt of the same metal is used as the electrolyte.
This method is widely used for the refining of metals like $Cu$,$Zn$,$Ni$,and $Ag$. Among the given options,$Cu$ is the most appropriate example.

(C) Zone refining is a technique based on the principle that the impurities are more soluble in the melt than in the solid state of the metal.
This method is particularly useful for producing semiconductors of very high purity,such as germanium $(Ge)$,silicon $(Si)$,and gallium $(Ga)$.

(A) $Mond's$ process is a method used for the refining of nickel $(Ni)$.
In this process,impure nickel is heated in a stream of carbon monoxide $(CO)$ to form a volatile complex,nickel tetracarbonyl $([Ni(CO)_4])$.
$\underset{\text{Impure}}{\text{Ni}} + 4CO \xrightarrow{330-350 \text{ K}} [Ni(CO)_4]$
This complex is then decomposed at a higher temperature to obtain pure nickel.
$[Ni(CO)_4] \xrightarrow{450-470 \text{ K}} \underset{\text{Pure}}{\text{Ni}} + 4CO$
Thus,the correct option is $A$.

(D) Zone refining is a method of purification used for semiconductors like $Si$,$Ge$,and $Ga$.

(D) Zone refining is the method used for obtaining metals and semiconductors in a state of high purity. In this process,a circular mobile heater is fixed at one end of a rod of the impure metal. As the heater moves,the pure metal crystallizes out of the melt and the impurities pass into the adjacent molten zone. This process is repeated several times to obtain high-purity silicon.

(B) The correct answer is $(B)$.
Nickel reacts with carbon monoxide to form a volatile complex known as nickel tetracarbonyl,$[Ni(CO)_4]$.
The reaction is: $Ni(s) + 4CO(g) \to [Ni(CO)_4](g)$.
This process is known as the $Mond$ process,which is used for the refining of nickel.

(C) The extraction of nickel is carried out by the $Mond$ process.
In this process,impure nickel is heated in a stream of carbon monoxide to form volatile nickel tetracarbonyl,$Ni(CO)_4$.
$Ni(s) + 4CO(g) \xrightarrow{330-350 \ K} Ni(CO)_4(g)$
This volatile complex is then subjected to higher temperatures,causing it to decompose into pure nickel and carbon monoxide.
$Ni(CO)_4(g) \xrightarrow{450-470 \ K} Ni(s) + 4CO(g)$
Therefore,the process involves both the formation and thermal decomposition of $Ni(CO)_4$.

(A) Mond's process is a chemical vapor deposition process used for the purification of nickel $(Ni)$.
In this process,impure nickel is heated in a stream of carbon monoxide $(CO)$ at $60-80 \ ^\circ C$ to form volatile nickel tetracarbonyl,$Ni(CO)_4$.
$Ni(s) + 4CO(g) \xrightarrow{60-80 \ ^\circ C} Ni(CO)_4(g)$
This volatile complex is then decomposed at a higher temperature $(180 \ ^\circ C)$ to obtain pure nickel.
$Ni(CO)_4(g) \xrightarrow{180 \ ^\circ C} Ni(s) + 4CO(g)$
Thus,the correct option is $(A)$.

(D) The given scheme represents the $Van-Arkel$ process.
This process is used for obtaining ultrapure metals.
In this method,the impure metal is converted into a volatile compound (usually an iodide),which leaves the impurities behind.
The volatile compound is then decomposed at a higher temperature to obtain the pure metal.
This method is specifically used for the purification of metals like $Ti$ and $Zr$.

(A) Annealing is a heat treatment process where steel is heated to a specific temperature (often to redness) and then allowed to cool slowly.
This process reduces internal stresses,increases ductility,and makes the steel soft and pliable.

(C) Wrought iron is the purest form of commercial iron,containing about $99.5 \%$ to $99.9 \%$ iron.
Due to its high purity,it has the highest melting point among the varieties of iron,which is approximately $1540^{\circ} \ C$.

(B) Annealing is a heat treatment process that involves heating a material to a specific temperature,holding it at that temperature for a suitable amount of time,and then cooling it slowly. In the context of steel,it involves heating the steel to a temperature above its critical range (bright redness) and then allowing it to cool slowly,typically in a furnace. This process reduces hardness,increases ductility,and helps eliminate internal stresses.

(A) This method is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal.
$A$ circular mobile heater is fixed at one end of a rod of the impure metal.
The molten zone moves along with the heater which is moved forward.
As the heater moves forward,the pure metal crystallises out of the melt and the impurities pass on into the adjacent molten zone.

(D) The correct option is $(D)$.
The Orford process is primarily used for the separation of $Ni$ and $Cu$ from their sulfide ores.
During the electrolytic refining of $Ni$ obtained from Orford bottoms,precious metals like $Pt$,$Au$,and $Ag$ collect as anode mud in a concentrated form,which is later processed to recover these metals.

(B) The extraction of silver from commercial lead (argentiferous lead) is carried out by $Parke's$ process.
In this process,zinc is added to the molten lead. Silver is more soluble in molten zinc than in molten lead,allowing it to be separated.

(A) The Park process is used for the desilverization of lead. In this process,zinc is added to the molten argentiferous lead. Silver is more soluble in molten zinc than in lead,allowing it to be separated from the lead impurities.

(C) Park's process is a metallurgical method used for the desilverization of lead. In this process,zinc is added to molten lead containing silver. Since silver is more soluble in molten zinc than in lead,it forms an alloy with zinc,which rises to the surface and is skimmed off. Thus,it is used in the extraction/purification of $Silver$.

(A) Parke's process is used for the extraction of silver from argentiferous lead.
It is based on the principle that the partition coefficient of silver between molten zinc and molten lead is very high.
When zinc is added to molten lead containing silver,silver preferentially dissolves in the molten zinc layer,which is immiscible with lead,allowing for its separation.

(D) Blister copper is the product obtained after the Bessemerization process in the extraction of copper. It contains approximately $98-99\%$ pure copper and about $1-2\%$ impurities. The name 'blister' arises because of the formation of blisters on the surface of the copper metal due to the evolution of $SO_2$ gas during the cooling process. Therefore,it is considered $1\%$ impure copper.

(C) During the electrolytic refining of copper,metals that are less reactive than copper,such as gold,silver,and platinum,do not dissolve in the electrolyte. Instead,they settle down at the bottom of the anode as $Anode \ mud$.

(A) The electrolytic refining of aluminum is known as $Hoop's$ process. In this process,an electrolytic cell is used with three layers of molten liquids of different densities. The impure aluminum forms the bottom layer (anode),the middle layer consists of molten fluorides,and the top layer is pure molten aluminum (cathode).

(C) The $Hoop$ process is an electrolytic refining method for $Al$.
In this cell,three layers of different densities are used.
The bottom layer consists of impure $Al$ (highest density),the middle layer consists of a molten mixture of $NaF$,$BaF_2$,and $AlF_3$ (intermediate density),and the top layer consists of pure $Al$ (lowest density).
These layers remain separated during electrolysis because they maintain different densities.

(D) In the electrolytic refining of copper,the impure metal is made the anode and a strip of pure metal is made the cathode.
Therefore,for a copper sample containing zinc as an impurity,the impure copper sample acts as the anode,and a strip of pure copper acts as the cathode.
During electrolysis,copper dissolves from the anode into the electrolyte,and pure copper deposits on the cathode.

(B) The given reaction represents the $Mond$ process for the refining of nickel.
In this process,impure nickel is heated in a stream of carbon monoxide $(CO)$ at $320 \ K$ to form a volatile complex,nickel tetracarbonyl $(Ni(CO)_4)$.
This complex is then decomposed at a higher temperature $(420 \ K)$ to obtain pure nickel metal.

(D) The $Van$ $Arkel$ method is used for the refining of metals like $Zr$ and $Ti$.
In this process,the metal is converted into a volatile iodide compound by reacting it with $I_2$ vapor at a specific temperature.
The reaction is: $Zr(s) + 2I_2(g) \xrightarrow{870K} ZrI_4(g)$.
The volatile $ZrI_4$ is then decomposed on a tungsten filament at a higher temperature $(2075K)$ to obtain pure $Zr$.

(C) Zone refining is a method used to obtain metals of very 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. This technique is particularly useful for producing semiconductors like $Si$,$Ge$,$Ga$,and $In$.

(D) During the electrolytic refining of copper,impure copper is used as the anode and pure copper as the cathode.
As the anode dissolves,the impurities that are less reactive than copper,such as $Ag$,$Au$,and $Pt$,do not dissolve and settle at the bottom of the electrolytic cell.
This collection of insoluble impurities is known as anode mud.
Therefore,all the given metals ($Ag$,$Au$,and $Pt$) are present in the anode mud.

(D) The zone refining method is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal. This method is mainly used for the purification of semiconductors like $Si$,$Ge$,and $Ga$ to a very high degree of purity.

(C) In the electrolytic refining of metals,the impure metal block is made the $Anode$ $(+)$ and a thin strip of pure metal is made the $Cathode$ $(-)$.
During electrolysis,the metal from the $Anode$ dissolves into the electrolyte solution as ions,and an equivalent amount of pure metal from the electrolyte deposits on the $Cathode$.

(A) The given reaction represents the $Van \ Arkel$ method for refining metals.
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 on a tungsten filament at a higher temperature $(1700 \ K)$ to obtain pure metal $(Ti)$.

(D) 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 molten zone moves along the metal rod,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.

(B) Cupellation is a refining process used for metals like $Ag$ (silver) and $Au$ (gold).
In this process,the impure metal is heated in a cupel (a shallow porous vessel) in a blast of air.
The base metal impurities (like $Pb$) are oxidized to their oxides,which are either absorbed by the porous cupel or volatilized,leaving behind the pure noble metal.

(C) Silver is refined by the process of $Cupellation$.
In this process,the impure silver containing lead as an impurity is heated in a cupel (a shallow porous vessel made of bone ash) in a blast of air.
The lead is oxidized to lead oxide $(PbO)$,which is absorbed by the cupel or blown away,leaving behind pure silver.