Reduction to free Metal Questions in English

(D) During the extraction of $Fe$ in a blast furnace,the impurity present is silica $(SiO_2)$.
To remove this acidic impurity,a basic flux,calcium oxide $(CaO)$,is added.
These react to form calcium silicate $(CaSiO_3)$,which is the slag.
The reaction is: $CaO(s) + SiO_2(s) \rightarrow CaSiO_3(l)$.

(B) In the Bessemer converter,copper sulphide $(Cu_2S)$ is partially oxidized to cuprous oxide $(Cu_2O)$.
This cuprous oxide then reacts with the remaining copper sulphide to produce metallic copper and sulphur dioxide gas.
The chemical reaction is: $Cu_2S + 2Cu_2O \to 6Cu + SO_2$.

(D) Flux is used to remove silica and undesirable metal oxide. It reacts with these impurities to form a fusible material called slag.

(A) . The $CN^{-}$ solution is used in the extraction of $Ag$ (silver) metal via the cyanide process (MacArthur-Forrest process).
The chemical reaction is: $4Ag + 8CN^{-} + 2H_2O + O_2 \rightarrow 4[Ag(CN)_2]^{-} + 4OH^{-}$.

(A) Smelting is a process of extracting a metal from its ore by heating it beyond the melting point in the presence of a reducing agent.
In most industrial smelting processes,carbon in the form of coke is used as the primary reducing agent to reduce metal oxides to their elemental form.
While carbon monoxide $(CO)$ is often the actual species that reduces the metal oxide,it is generated from the carbon source $(C)$ within the furnace.
Therefore,$C$ (carbon) is the correct choice as the reducing agent used in smelting.

(C) The inner lining of a blast furnace is constructed using fire-clay bricks because they can withstand very high temperatures without melting or reacting with the charge.

(C) In the extraction of iron,limestone $(CaCO_3)$ is used as a flux.
It decomposes to give $CaO$,which reacts with the silica $(SiO_2)$ impurity to form slag $(CaSiO_3)$.
$CaCO_3 \xrightarrow{\Delta} CaO + CO_2$
$CaO + SiO_2 \rightarrow CaSiO_3$ (Slag)

(A) The reaction between copper$(I)$ sulfide and copper$(I)$ oxide is known as auto-reduction or self-reduction.
The balanced chemical equation is: $2Cu_2O + Cu_2S \to 6Cu + SO_2$.
This process is carried out in a reverberatory furnace to obtain metallic copper.

(C) The electrometallurgical process (electrolysis) is used for the extraction of highly reactive metals like $Na$,$Mg$,$Ca$,and $Al$.
These metals are very reactive and cannot be reduced by common reducing agents like $C$ or $CO$.
Therefore,they are extracted by the electrolysis of their fused salts.

(A) The correct answer is $(A)$.
Carbon reduction is the most common and general method for extracting metals from their oxide ores.
For example,in the extraction of iron from hematite $(Fe_2O_3)$,carbon is used as a reducing agent:
$Fe_2O_3 + 3C \to 2Fe + 3CO$.

(B) In the process of smelting,a flux is added to react with the non-fusible gangue (impurities) present in the ore to form a fusible material known as slag. The reaction is represented as: $Flux + Gangue \to Slag$.

(B) The alumino-thermic process (thermite process) is used for the extraction of metals like $Cr$,$Mn$,and $Fe$ from their oxides.
These metals have a high affinity for oxygen,making their oxides very stable and difficult to reduce using common reducing agents like carbon or hydrogen.
Aluminum acts as a strong reducing agent because the formation of $Al_2O_3$ is highly exothermic,providing the necessary energy for the reduction process.
Example: $Cr_2O_3 + 2Al \to Al_2O_3 + 2Cr$ $(\Delta H = -ve)$.

(B) In the blast furnace,the reduction of iron oxide $(Fe_2O_3)$ primarily occurs through carbon monoxide $(CO)$.
The chemical reaction is: $Fe_2O_3 + 3CO \to 2Fe + 3CO_2$.

(C) Furnaces are lined with $CaO$ because it is a refractory material with a very high melting point and it is basic in nature,which helps in removing acidic impurities during the extraction process.

(C) The electrolytic method of reduction is used for the extraction of highly reactive metals,which are strongly electropositive. These metals have a high affinity for oxygen and cannot be reduced by common reducing agents like carbon or hydrogen. Examples include $Na$,$Mg$,$Ca$,and $Al$.

(B) The carbon reduction process is used for metals that have a lower affinity for oxygen than carbon at high temperatures.
$Al$ is a highly electropositive metal with a very high affinity for oxygen.
Therefore,it cannot be reduced by carbon.
Instead,$Al$ is extracted by the electrolytic reduction of its molten ore.

(D) The carbon reduction process (smelting) is commonly used for the extraction of iron from its oxide ores like hematite $(Fe_2O_3)$.
The chemical reaction is:
$Fe_2O_3 + 3C \to 2Fe + 3CO$
Therefore,the correct option is $(d)$.

(C) The reduction of metal oxides by carbon is possible only for metals that have a lower affinity for oxygen than carbon at a given temperature.
Highly reactive metals like $Ca$ and $K$ have a very high affinity for oxygen,and their oxides ($CaO$ and $K_2O$) are thermodynamically very stable.
Therefore,these oxides cannot be reduced by carbon to their respective metals.

(B) Metals like $Aluminium$ and $Magnesium$ are highly reactive and are extracted by electrolytic reduction. $Copper$ is typically extracted by self-reduction or pyrometallurgy. $Iron$ is extracted from its oxide ores (like $Fe_2O_3$) by thermal reduction using carbon (coke) in a blast furnace. Therefore,$Iron$ is the correct answer.

(A) . Bauxite into aluminium is not suitable for chemical reduction because $Al$ is a very strong reducing agent.
It has a much stronger affinity for oxygen than carbon,making it impossible to reduce $Al_2O_3$ using carbon as a reducing agent.

(C) In the alumino-thermite process,aluminium $(Al)$ is used to reduce metal oxides (like $Fe_2O_3$) to their respective metals.
Since aluminium undergoes oxidation $(Al \rightarrow Al^{3+} + 3e^-)$ and reduces the metal oxide,it acts as a reducing agent.

(B) Aluminium $(Al)$ is extracted by the electrolytic reduction method (Hall-Heroult process).
In this process,alumina $(Al_2O_3)$ is dissolved in molten cryolite $(Na_3AlF_6)$ and fluorspar $(CaF_2)$,which lowers the melting point of the mixture and increases electrical conductivity.
Electrolysis is carried out in a steel tank lined with carbon (acting as cathode),and graphite rods are used as the anode.
During electrolysis,aluminium is deposited at the cathode,while oxygen gas is liberated at the anode.

(D) Aluminium is prepared in large quantities by the $Hall-Heroult$ process,which involves the electrolysis of $Al_2O_3$ dissolved in molten $Na_3AlF_6$ (cryolite) and $CaF_2$ (fluorspar).

(A) In the metallurgy of aluminium,purified $Al_2O_3$ (alumina) is used as the electrolyte source.
It is mixed with $Na_3AlF_6$ (cryolite) or $CaF_2$ (fluorspar),which lowers the melting point of the mixture and increases its electrical conductivity.
This electrolytic process is known as the $Hall-Heroult$ process.
The overall reaction is: $2 Al_2O_3 + 3 C \rightarrow 4 Al + 3 CO_2$.

(C) The extraction of aluminium from bauxite involves the $Hall-Heroult$ process.
In this process,purified alumina $(Al_2O_3)$ is dissolved in molten cryolite $(Na_3AlF_6)$ and fluorspar $(CaF_2)$,which lowers the melting point of the mixture and increases conductivity.
Aluminium is then obtained by $Electrolytic \text{ } reduction$ of the molten mixture.

(A) The thermite process involves the reduction of metal oxides using a more reactive metal,such as aluminum $(Al)$. This process is specifically used for metals whose oxides are highly stable and cannot be easily reduced by carbon $(C)$.

(B) The extraction of iron from its ore $Fe_2O_3$ (hematite) on a large scale is carried out in a blast furnace.
In the blast furnace,$CO$ acts as the primary reducing agent.
The chemical reaction is: $Fe_2O_3 + 3CO \to 2Fe + 3CO_2$.

(C) The correct answer is $C$.
During the extraction of copper from copper glance $(Cu_2S)$,the ore is partially roasted to form copper$(I)$ oxide $(Cu_2O)$.
$2Cu_2S + 3O_2 \to 2Cu_2O + 2SO_2$
Subsequently,the remaining $Cu_2S$ reacts with the formed $Cu_2O$ to produce metallic copper. This process is known as self-reduction or auto-reduction.
$2Cu_2O + Cu_2S \to 6Cu + SO_2$

(A) In the extraction of zinc from zinc oxide $(ZnO)$,carbon monoxide $(CO)$ or coke $(C)$ is used as a reducing agent.
The chemical reaction is: $ZnO + CO \to Zn + CO_2$.

(A) In the Hall-$H$éroult process,alumina $(Al_2O_3)$ is dissolved in a mixture of fused cryolite $(Na_3AlF_6)$ and fluorspar $(CaF_2)$.
Cryolite lowers the melting point of the mixture and increases its electrical conductivity.
Fluorspar $(CaF_2)$ acts as a flux to make the fused mixture more conducting and fluid.

(B) Electrometallurgy is a process of extraction of metals by electrolysis of their fused salts.
It is used for the extraction of highly reactive metals like $Na$,$Mg$,$Ca$,and $Al$ because these metals cannot be reduced by common reducing agents like carbon or hydrogen.

(C) Highly reactive metals like $Na$,$Mg$,and $Ca$ are extracted by the electrolysis of their fused salts because they cannot be reduced by common reducing agents like carbon.
Therefore,$Sodium$ $(Na)$ is extracted by the electrolysis of fused $NaCl$.

(D) The Alumino-thermic process (or Goldschmidt process) involves the reduction of metal oxides (like $Fe_2O_3$ or $Cr_2O_3$) using aluminum powder as a reducing agent.
This process is primarily used for the extraction of metals like $Fe$,$Cr$,and $Mn$,which are not easily reduced by carbon.
Since $Fe$,$Cr$,and $Mn$ are not listed in options $A$,$B$,or $C$,the correct answer is $D$.

(A) The reduction of metal oxides like $Cr_2O_3$ is carried out using aluminum powder,which is known as the Alumino-thermic process or Goldschmidt process.
The chemical reaction is: $Cr_2O_3 + 2Al \to Al_2O_3 + 2Cr$.

(A) The correct answer is $A$.
In the thermite process,a mixture of aluminium powder and metal oxide (such as ferric oxide) is used to reduce the metal ore.
The reaction is highly exothermic: $Fe_2O_3 + 2Al \rightarrow 2Fe + Al_2O_3 + \text{Heat}$.

(B) The process of heating an ore with carbon in the absence of air is known as carbon reduction.
This process is commonly used in the extraction of metals like iron in a blast furnace.
The chemical reaction is: $Fe_2O_3 + 3C \rightarrow 2Fe + 3CO$.

(B) The cyanide process,also known as the Mac-Arthur Forrest process,is primarily used for the extraction of noble metals like $Ag$ (silver) and $Au$ (gold) from their ores.
In this process,the crushed ore is treated with a dilute solution of $NaCN$ or $KCN$ in the presence of air (as a source of $O_2$),which dissolves the metal as a cyano-complex.
For silver $(Ag)$: $4Ag(s) + 8CN^-(aq) + 2H_2O(aq) + O_2(g) \rightarrow 4[Ag(CN)_2]^-(aq) + 4OH^-(aq)$.
The metal is then recovered from the complex by displacement with a more electropositive metal like $Zn$.

(C) Hydrometallurgy is the process of extracting a metal from its ore by dissolving the metal or its ore in a suitable chemical reagent,followed by the recovery of the metal using a precipitating agent.
Gold is extracted by leaching with a dilute solution of $NaCN$ or $KCN$ in the presence of air $(O_2)$,which acts as an oxidizing agent to form a water-soluble complex.
$4Au(s) + 8CN^-(aq) + 2H_2O(aq) + O_2(g) \to 4[Au(CN)_2]^-(aq) + 4OH^-(aq)$
The gold is then recovered from the complex by displacement using a more electropositive metal like zinc:
$2[Au(CN)_2]^-(aq) + Zn(s) \to 2Au(s) + [Zn(CN)_4]^{2-}(aq)$

(B) Auto reduction is used for the extraction of copper from its ore with low copper content. In this process,the sulfide ore is partially roasted to form oxide,which then reacts with the remaining sulfide to produce the metal without the need for an external reducing agent.

(B) The extraction of $Pb$ (Lead) from its ore $PbS$ (Galena) involves self-reduction.
$2PbO + PbS \xrightarrow{\Delta} 3Pb + SO_2 \uparrow$
$PbSO_4 + PbS \xrightarrow{\Delta} 2Pb + 2SO_2 \uparrow$
The extraction of $Sn$ (Tin) from its ore $SnO_2$ (Cassiterite) involves carbon reduction.
$SnO_2 + 2C \xrightarrow{\Delta} Sn + 2CO$
Therefore,$Pb$ is extracted by self-reduction and $Sn$ is extracted by carbon reduction.

(C) The correct answer is $C$.
$Mysore$ $Iron$ $and$ $Steel$ $Limited$ (now known as $Visvesvaraya$ $Iron$ $and$ $Steel$ $Plant$) was established in $1923$ at $Bhadravati$.
Initially,it used charcoal as a fuel source for its blast furnaces because of the proximity to forests.
Later,it switched to hydroelectric power generated from the $Sharavathi$ river project.

(A) Metals that are lower in the reactivity series can be reduced by hydrogen.
Copper $(II)$ oxide $(CuO)$ is less reactive than hydrogen and can be reduced to metallic copper by heating in a stream of hydrogen gas:
$CuO(s) + H_2(g) \rightarrow Cu(s) + H_2O(g)$.
Magnesium,aluminium,and calcium are highly reactive metals,and their oxides cannot be reduced by hydrogen.

(D) The stability of metal oxides is related to the standard Gibbs free energy of formation. Among the given options,$Ag_2O$ is the least stable oxide at room temperature. It decomposes easily upon heating:
$Ag_2O \xrightarrow{\Delta} 2Ag + \frac{1}{2}O_2$
Other oxides like $ZnO$,$CuO$,and $Sb_2O_3$ are significantly more stable and do not decompose at room temperature.

(C) The given equation represents the extraction of gold $(Au)$ or silver $(Ag)$ from their native ores using cyanide solution,a process known as Mac-Arthur-Forrest cyanide process.
The balanced chemical equation for the extraction of gold is:
$4Au + 8CN^- + 2H_2O + O_2 \xrightarrow{} 4[Au(CN)_2]^- + 4OH^-$
Here,the metal $M$ is $Au$ (Gold).

(D) The most modern method for steel production is the $L.D.$ (Linz-Donawitz) process,which uses high-purity oxygen to refine molten pig iron.

(C) In the basic Bessemer process,the converter is lined with basic refractory materials like $CaO$ (lime) and $MgO$ (magnesia).
These materials are used because they have very high melting points and can withstand the high temperatures required for steel production while resisting the basic slag formed during the process.

(A) The process of producing a hard surface coating of iron nitride on steel is known as nitriding.
In this process,steel is heated in an atmosphere of ammonia $(NH_3)$ at temperatures typically between $500 \ ^\circ C$ and $550 \ ^\circ C$.

(D) In the blast furnace,different temperature zones exist for the reduction of iron oxides.
At the lower temperature range of $400\,^{\circ}C - 600\,^{\circ}C$ (upper part of the furnace),the reduction of hematite $(Fe_2O_3)$ occurs as follows:
$3Fe_2O_3 + CO \to 2Fe_3O_4 + CO_2$
Therefore,the correct reaction is $3Fe_2O_3 + CO \to 2Fe_3O_4 + CO_2$.

(B) The correct answer is $(B)$.

Type of Iron	Carbon Content (%)
Cast iron	$2.5 - 4.0\%$
Wrought iron	$0.12 - 0.25\%$
Steel	$0.2 - 1.5\%$

Based on the table,Wrought iron contains the lowest percentage of carbon.

(A) The $Siemens-Martin$ open hearth process is considered the best method for manufacturing high-quality steel.
This process allows for better control over the composition of the steel and the removal of impurities compared to the $Bessemer$ process.
It also facilitates the recycling of scrap steel,which improves the quality and consistency of the final product.