Reduction to free Metal Questions in English

(C) Medical instruments are typically manufactured from stainless steel,which is a type of steel alloy containing $Cr$ and $Ni$ to provide corrosion resistance and durability. Therefore,the correct option is $C$.

(B) The Bessemer process was the first inexpensive industrial process for the mass production of $Steel$ from molten pig iron. The process is carried out in the Bessemer converter,where air is blown through the molten iron to oxidize impurities like carbon,silicon,and manganese.

(D) The carbon content in different forms of iron is as follows:
$1$. Wrought iron: $0.12-0.25\% \text{ carbon}$.
$2$. Steel: $0.25-2.0\% \text{ carbon}$.
$3$. Pig iron: $3.0-4.5\% \text{ carbon}$.
Thus,the carbon content in steel is intermediate between that of wrought iron and pig iron.

(C) The carbon content in different forms of iron is as follows:
$1$. Wrought iron is the purest form of iron with carbon content less than $0.15\%$.
$2$. Steel is an alloy of iron with carbon content ranging from $0.15\%$ to $2.0\%$.
$3$. Pig iron is the most impure form of iron with carbon content over $2\%$.

(B) In the $Bessemer$ process,a blast of air is blown through the molten pig iron to oxidize impurities like carbon,silicon,and manganese.
In the $open-hearth$ process,$ferric \ oxide$ $(Fe_2O_3)$ or iron ore is added to the molten metal to oxidize the excess carbon present in the pig iron.

(B) The basic open-hearth process is specifically designed to remove phosphorus impurities from pig iron by using a basic lining (such as $CaO$ or $MgO$) and adding limestone $(CaCO_3)$ to the charge.
Therefore,the statement that 'Phosphorus impurity cannot be removed by this process' is incorrect,as this process is highly effective at removing phosphorus.
Other statements like adding limestone,controlling carbon content,and utilizing iron scrap are correct features of the basic open-hearth process.

(C) Cast iron is made from pig iron by melting it with scrap iron and coke using a hot air blast. It contains about $3\%$ carbon. It is extremely hard and brittle. Unlike most metals,cast iron expands on solidification (cooling) due to the presence of graphite. It is not corrosion resistant. Therefore,the statement that it is corrosion resistant is incorrect.

(D) . Firstly,carbon which is added along with crushed haematite ore is oxidised to $CO$ (and $CO_2$).
Secondly,the produced $CO$ acts as the chief reducing agent for the reduction of haematite $(Fe_2O_3)$ to iron,which is then processed into steel.

(B) Magnetite $(Fe_3O_4)$ is an oxide ore of iron.
In the blast furnace,iron oxides are reduced to metallic iron using carbon (coke) as the reducing agent.
The reaction is: $Fe_3O_4 + 4C \rightarrow 3Fe + 4CO$.

(B) Commercially,copper sulphate is prepared by the action of dilute $H_2SO_4$ on copper scraps in the presence of air (oxygen).
The chemical reaction is:
$2Cu + 2H_2SO_4 + O_2 \to 2CuSO_4 + 2H_2O$

(A) The extraction of silver from its ore,argentite $(Ag_2S)$,involves the cyanide process.
In this process,the ore is treated with a dilute solution of sodium cyanide $(NaCN)$ in the presence of air.
The chemical reaction is: $Ag_2S + 4NaCN \rightarrow 2Na[Ag(CN)_2] + Na_2S$.
The product formed is sodium dicyanoargentate$(I)$,which is $Na[Ag(CN)_2]$.

(B) The extraction of silver $(Ag)$ from its ore (like $Ag_2S$) involves leaching with a dilute solution of $NaCN$ in the presence of air $(O_2)$:
$Ag_2S + 4NaCN \to 2Na[Ag(CN)_2] + Na_2S$
$2Na_2S + 2O_2 + H_2O \to 2NaOH + Na_2S_2O_3$
Silver is then recovered from the complex by displacement using zinc dust:
$2Na[Ag(CN)_2] + Zn \to Na_2[Zn(CN)_4] + 2Ag$

(D) The correct option is $(D)$.
In the Mc Arthur Forest method,silver is extracted from the solution of sodium argenticyanide by using zinc $(Zn)$ as a reducing agent.
The chemical reaction is as follows:
$2Na[Ag(CN)_2] + Zn \xrightarrow{} Na_2[Zn(CN)_4] + 2Ag \downarrow$

(C) The iron obtained from a blast furnace contains about $4 \%$ carbon and many impurities like $S$,$P$,$Si$,and $Mn$. This form of iron is known as $Pig \ iron$.

(D) The extraction of silver from argentite $(Ag_2S)$ involves the Mac-Arthur Forrest cyanide process.
First,the ore is treated with a dilute solution of $NaCN$ to form a soluble complex:
$Ag_2S + 4NaCN \to 2Na[Ag(CN)_2] + Na_2S$
Then,the silver is displaced from the complex by adding a more reactive metal like zinc:
$2Na[Ag(CN)_2] + Zn \to Na_2[Zn(CN)_4] + 2Ag$

(B) In the extraction of $Zn$ (zinc),$Producer \ gas$ is burnt in the jackets surrounding the retorts to maintain the required high temperature for the reduction process.

(C) The $MacArthur-Forrest$ process,also known as the cyanide process,is a hydrometallurgical technique used for extracting gold $(Au)$ from low-grade ores.
In this process,the crushed ore is treated with a dilute solution of sodium cyanide $(NaCN)$ in the presence of air $(O_2)$,which dissolves the gold as a soluble complex,$Na[Au(CN)_2]$.

(D) In the metallurgy of zinc,the zinc dust obtained from the reduction of $ZnO$ often contains some impurities of $ZnO$ itself. This zinc dust is purified by the process of smelting,where the mixture is heated to a high temperature to separate the metal from the oxide impurities.

(C) In the metallurgy of copper,the process is known as self-reduction or auto-reduction.
First,partial roasting of copper$(I)$ sulfide occurs: $2Cu_2S + 3O_2 \to 2Cu_2O + 2SO_2$.
Then,the remaining copper$(I)$ sulfide reacts with the copper$(I)$ oxide formed to produce metallic copper: $Cu_2S + 2Cu_2O \to 6Cu + SO_2$.

(D) During the smelting of roasted copper pyrites $(CuFeS_2)$,the ore is heated with silica $(SiO_2)$ and coke.
Iron has a higher affinity for sulphur than copper.
Therefore,the sulphur preferentially combines with iron to form ferrous sulphide $(FeS)$.
The remaining copper forms cuprous sulphide $(Cu_2S)$.
The iron sulphide $(FeS)$ is then oxidized to ferrous oxide $(FeO)$,which reacts with silica to form slag $(FeSiO_3)$.
The primary reaction is: $2CuFeS_2 + O_2 \rightarrow Cu_2S + 2FeS + SO_2$.

(C) In the metallurgy of copper,the Bessemer converter is used for the self-reduction process.
First,a part of the copper$(I)$ sulphide is oxidized to copper$(I)$ oxide:
$2Cu_2S + 3O_2 \to 2Cu_2O + 2SO_2$
Then,the copper$(I)$ oxide reacts with the remaining copper$(I)$ sulphide to produce metallic copper:
$2Cu_2O + Cu_2S \to 6Cu + SO_2$
Both reactions occur in the converter,but the final step that produces metallic copper is the self-reduction reaction.

(C) Parke's process is a metallurgical method used for the desilverization of lead.
It is specifically used to extract silver from argentiferous lead (lead containing silver as an impurity) by adding zinc to the molten lead.

(C) In the smelting process of copper extraction,the roasted ore (containing $Cu_2S$ and $FeS$) is mixed with silica $(SiO_2)$ and heated in a blast furnace.
$1$. $FeS$ is oxidized to $FeO$: $2FeS + 3\,O_2 \to 2\,FeO + 2\,SO_2 \uparrow$.
$2$. $FeO$ reacts with silica to form slag: $FeO + SiO_2 \to FeSiO_3$.
$3$. If any $Cu_2O$ is formed,it reacts with $FeS$ to form $Cu_2S$: $Cu_2O + FeS \to Cu_2S + FeO$.
Option $C$ represents the partial roasting reaction,which occurs during the roasting stage,not the smelting stage,as smelting primarily involves the formation of matte $(Cu_2S + FeS)$ and slag $(FeSiO_3)$.

(D) The extraction of $Cu$ (Copper) involves the process of bessemerisation.
In the Bessemer converter,the impurity of $FeO$ (Ferrous Oxide) reacts with $SiO_2$ (Silica) to form $FeSiO_3$ (Slag).
$FeO + SiO_2 \xrightarrow{} FeSiO_3$ (Slag)
Subsequently,the remaining $Cu_2S$ reacts with $Cu_2O$ to produce blister copper.
$2Cu_2O + Cu_2S \xrightarrow{} 6Cu + SO_2 \uparrow$

(A) The Bessemer converter is used to convert $Pig \ Iron$ into $Steel$ by blowing air through the molten metal to oxidize impurities like $C$,$Si$,and $Mn$.
$2Mn + O_2 \xrightarrow{} 2MnO$
$Si + O_2 \xrightarrow{} SiO_2$
$2C + O_2 \xrightarrow{} 2CO$
$MnO + SiO_2 \xrightarrow{} MnSiO_3$ (Slag)
Thus,the primary purpose of the Bessemer process is the manufacturing of $Steel$ from $Pig \ Iron$.

(A) In the cyanide process (MacArthur-Forrest process) for the extraction of silver $(Ag)$,the ore is treated with a dilute solution of sodium cyanide $(NaCN)$ in the presence of air $(O_2)$.
$4Ag(s) + 8CN^-(aq) + 2H_2O(aq) + O_2(g) \rightarrow 4[Ag(CN)_2]^-(aq) + 4OH^-(aq)$.
Here,silver is oxidized and converted into a soluble dicyanoargentate$(I)$ complex,$[Ag(CN)_2]^-$,which allows it to be separated from the ore.

(C) The most impure form of iron is $Pig \ Iron$.
It is obtained directly from the blast furnace and contains about $4 \%$ carbon and many impurities like $S$,$P$,$Si$,and $Mn$.

(B) During the extraction of copper,the final step involves the reduction of copper$(I)$ oxide $(Cu_2O)$ with copper$(I)$ sulphide $(Cu_2S)$ to produce metallic copper and sulphur dioxide gas $(SO_2)$:
$2Cu_2O + Cu_2S \rightarrow 6Cu + SO_2 \uparrow$
When the molten copper is cooled,the dissolved $SO_2$ gas escapes,creating bubbles on the surface of the solidified metal,which gives it a blistered appearance. Hence,it is known as blister copper.

(B) Wrought iron is the purest form of commercial iron,containing approximately $99.5 \%$ to $99.9 \%$ iron. It is prepared from cast iron by oxidizing impurities in a reverberatory furnace lined with hematite $(Fe_2O_3)$.

(B) Spelter is the commercial name for impure zinc.
It is obtained by the reduction of zinc oxide with carbon in a blast furnace.
The zinc obtained contains impurities like $Fe$,$Pb$,$Cd$,and $As$.

(B) The extraction of silver $(Ag)$ from its ore $(Ag_2S)$ involves the formation of a soluble complex ion,sodium dicyanoargentate$(I)$.
The chemical reactions are:
$Ag_2S + 4NaCN \rightleftharpoons 2Na[Ag(CN)_2] + Na_2S$
$2Na[Ag(CN)_2] + Zn \to Na_2[Zn(CN)_4] + 2Ag \downarrow$
Here,$[Ag(CN)_2]^-$ is the complex ion formed during the process.

(A) The extraction of gold involves the leaching of gold ore with a dilute solution of $NaCN$ or $KCN$ in the presence of air $(O_2)$,which acts as an oxidizing agent.
The reaction is: $4Au(s) + 8CN^{-}(aq) + 2H_2O(aq) + O_2(g) \to 4[Au(CN)_2]^{-}(aq) + 4OH^{-}(aq)$.
Thus,$[X] = [Au(CN)_2]^{-}$.
Gold is then recovered from the complex by displacement using zinc $(Zn)$:
$2[Au(CN)_2]^{-}(aq) + Zn(s) \to [Zn(CN)_4]^{2-}(aq) + 2Au(s)$.
Thus,$[Y] = [Zn(CN)_4]^{2-}$.

(A) $Al_2O_3$ (Aluminum oxide) has a very high negative value of Gibbs free energy of formation $(\Delta G_f^\circ)$,which makes it extremely stable. Due to this high stability,it cannot be reduced by common chemical reducing agents like carbon or hydrogen.

(C) In the alumino-thermite process,$Al$ acts as a reducing agent.
The chemical reaction is: $2Al + Fe_2O_3 \rightarrow Al_2O_3 + 2Fe$.

(B) The melting point of the mixture of $NaCl + CaCl_2$ is lower than the melting point of pure $NaCl$,which allows the electrolysis process to occur at a lower temperature.

(A) Limestone $(CaCO_3)$ is used in the production of Portland cement,extraction of iron from hematite (as a flux),and the Solvay process for sodium carbonate production. However,it is not used in the extraction of phosphorus from phosphorite.

(D) In the MacArthur-Forrest process,silver is extracted from the cyanide complex solution by using zinc as a reducing agent. The chemical reaction is: $2Na[Ag(CN)_2] + Zn \rightarrow Na_2[Zn(CN)_4] + 2Ag$.

(D) The extraction of copper from its ore involves the self-reduction process,also known as auto-reduction. When a mixture of $Cu_2O$ and $Cu_2S$ is heated,the following reaction occurs:
$2Cu_2O + Cu_2S \rightarrow 6Cu + SO_2$
Thus,copper metal and sulfur dioxide gas are produced.

(B) During the extraction of copper from copper pyrites $(CuFeS_2)$,the ore is roasted to form $FeO$ and $Cu_2S$.
$FeO$ is a basic impurity.
To remove this basic impurity,an acidic flux,$SiO_2$,is added.
$FeO + SiO_2 \rightarrow FeSiO_3$ (slag).
Thus,the flux is $SiO_2$ and it is acidic in nature.

(A) The extraction of aluminum is primarily carried out by the Hall-Heroult process.
In this process,pure $Al_2O_3$ is dissolved in molten cryolite $(Na_3AlF_6)$ along with a small amount of fluorspar $(CaF_2)$.
These fluorides ($Al, Na, Ba$ or $Ca$) are used to lower the melting point of the mixture and increase its electrical conductivity.
Therefore,the correct electrolyte mixture consists of the fluorides of $Al, Na$ and $Ba$ (or $Ca$).

(D) In the extraction of iron from its ore magnetite $(Fe_3O_4)$,carbon monoxide $(CO)$ is used as a reducing agent in the blast furnace.
The chemical reaction is as follows:
$Fe_3O_4 + 4CO \rightarrow 3Fe + 4CO_2$
Thus,$CO$ is the correct reducing agent.

(B) Thermal reduction (smelting) is typically used for metals with moderate reactivity,such as $Fe$,$Pb$,$Zn$,and $Sn$.
In the extraction of iron $(Fe)$,the oxide ore (hematite,$Fe_2O_3$) is reduced using carbon monoxide $(CO)$ or coke in a blast furnace.
Metals like $Al$ and $Mg$ are highly reactive and are extracted via electrolytic reduction,while $Cu$ is often extracted via self-reduction or roasting followed by reduction.
Therefore,$Fe$ is the correct answer.

(B, C, D) The process of using $Al$ as a reducing agent to extract metals from their oxides is known as the $Aluminothermic$ process or $Goldschmidt$ process.
This process is suitable for metal oxides that are less stable than $Al_2O_3$ but have high melting points,such as $Cr_2O_3$,$MnO_2$,and $V_2O_5$.
$Na_2O$ cannot be reduced by $Al$ because $Na$ is more electropositive than $Al$,and $Na_2O$ is more stable than $Al_2O_3$.
Therefore,$Cr$,$Mn$,and $V$ can be obtained using $Al$ as a reducing agent.

(B) In the Ellingham diagram ($\Delta G^\circ$ vs $T$ plot),the line for the formation of $Cu_2O$ lies above the line for the oxidation of $C$ to $CO$ at lower temperatures.
Therefore,$C$ can reduce $Cu_2O$ to $Cu$.
The reaction is: $Cu_2O + C \rightarrow 2Cu + CO$.

(A) The $Mac$ $Arthur$ process,also known as the $Mac$ $Arthur-Forrest$ cyanide process,is a hydrometallurgical technique used for the extraction of gold $(Au)$ and silver $(Ag)$ from low-grade ores.
In this process,the crushed ore is treated with a dilute solution of sodium cyanide $(NaCN)$ in the presence of air $(O_2)$,which acts as an oxidizing agent.
The metal dissolves to form a soluble complex,such as $[Ag(CN)_2]^-$,from which the metal is later recovered by displacement using a more electropositive metal like zinc $(Zn)$.

(B) During the smelting of roasted copper ore,the ore contains iron as an impurity in the form of $FeO$.
Silica $(SiO_2)$ is added as a flux to remove this $FeO$ as slag.
The reaction is: $FeO + SiO_2 \rightarrow FeSiO_3$ (ferrous silicate slag).
Thus,silica is added to remove ferrous oxide.

(B) The extraction of gold from its native ore involves leaching with a dilute solution of sodium cyanide $(NaCN)$ or potassium cyanide $(KCN)$ in the presence of air (which provides $O_2$).
The chemical reaction is:
$4Au(s) + 8CN^-(aq) + 2H_2O(aq) + O_2(g) \rightarrow 4[Au(CN)_2]^-(aq) + 4OH^-(aq)$
Thus,the soluble complex formed is $[Au(CN)_2]^-$,which is dicyanoaurate$(I)$ ion.

(B) During the extraction of copper from copper pyrites $(CuFeS_2)$,the ore is roasted to convert iron sulfide $(FeS)$ into iron oxide $(FeO)$.
$2FeS + 3O_2 \rightarrow 2FeO + 2SO_2$
Then,silica $(SiO_2)$ is added as a flux to remove the iron oxide impurity.
$FeO + SiO_2 \rightarrow FeSiO_3$ (Slag)
Thus,the slag formed is iron silicate $(FeSiO_3)$.

(B) In the blast furnace,the reduction of iron oxides ($Fe_2O_3$ or $Fe_3O_4$) occurs primarily by carbon monoxide $(CO)$.
At lower temperatures $(500-800 \ K)$,$Fe_2O_3$ is reduced by $CO$ as follows:
$3Fe_2O_3 + CO \rightarrow 2Fe_3O_4 + CO_2$
$Fe_3O_4 + 4CO \rightarrow 3Fe + 4CO_2$
At higher temperatures $(900-1500 \ K)$,the reaction is:
$FeO + CO \rightarrow Fe + CO_2$
Thus,$CO$ acts as the main reducing agent.

(B) The Alumino-thermite process involves the reduction of metal oxides (like $Cr_2O_3$ or $MnO_2$) using aluminum powder as a reducing agent.
The reaction is highly exothermic: $Cr_2O_3 + 2Al \rightarrow 2Cr + Al_2O_3 + \text{Heat}$.
In this reaction,aluminum gets oxidized to $Al_2O_3$ and reduces the metal oxide to its corresponding metal.
Therefore,aluminum acts as a reducing agent.