Question

The carbon-based reduction method is not used for the extraction of:
[This question has multiple correct options]
(A) Tin from $Sn{O_2}$
(B) Iron from $F{e_2}{O_3}$
(C) Aluminium from $A{l_2}{O_3}$
(D) Magnesium from $MgC{O_3}.CaC{O_3}$

Answer 1

In this method of carbon-based reduction the metal ore is decomposed by treating the ore with heat and a chemical reducing agent like a carbon source to extract the metal. The oxides which have a higher affinity for oxygen than carbon, cannot be reduced using carbon.

Complete step by step answer:
-First of all let us see what this process of carbon-based reduction method is.
When any element undergoes carbon-based reduction, its mineral form is reacted with carbon and the carbon atom gets oxidised to form either CO (Carbon monoxide) or $C{O_2}$ (Carbon dioxide). This is how the carbon behaves like a reducing agent and helps in the extraction of the metal. This process is basically known as smelting.
According to proper terms and terminology smelting can be defined as the process in which we use heat and a chemical reducing agent to decompose the ore and extract the required metal. The other elements present in the ore will be removed in the form of gases or slag and a carbon source will act as the chemical reducing agent which will help remove the oxygen present in the ore
-Now let us see each option to see which of them can be extracted using carbon by this process of reduction using carbon or smelting.

For (A) Tin from $Sn{O_2}$: When $Sn{O_2}$ reacts with C, the carbon gets reduced to form CO (Carbon monoxide) and Sn is formed. The involved reaction is:
$Sn{O_2} + 2C \to Sn + 2CO$
So, tin can be obtained by carbon reduction of $Sn{O_2}$.

For (B) Iron from $F{e_2}{O_3}$: Iron is obtained by reducing its ore in the blast furnace using carbon as a reducing agent. The reactions occurring in the blast furnace are:
$F{e_2}{O_3} + C \to 2FeO + CO$
$FeO + C \to Fe + CO$
This is how iron is obtained by carbon reduction of $F{e_2}{O_3}$.

For (C) Aluminium from $A{l_2}{O_3}$: Aluminium has a higher affinity for oxygen than carbon and hence carbon cannot be used to reduce an oxide of aluminium. The reaction involved by the reaction of $A{l_2}{O_3}$ with carbon is:
$A{l_2}{O_3} + C \to A{l_2}{C_3} + {O_2}$
So, we can say that aluminium cannot be extracted from $A{l_2}{O_3}$ by the process of carbon reduction.

For (D) Magnesium from $MgC{O_3}.CaC{O_3}$: This ore is a carbonate and carbonates first undergo calcination. This ore after calcination will form CaO and MgO. They have an affinity for carbon. So, the reaction of CaO and MgO with carbon will be:
$CaO + C \to Ca{C_2}$; and $MgO + 2C \to Mg{C_2}$
So, we cannot obtain magnesium from $MgC{O_3}.CaC{O_3}$ by the method of carbon reduction.

-Hence we can finally conclude that we cannot obtain Al from $A{l_2}{O_3}$ and Mg from $MgC{O_3}.CaC{O_3}$ by the method of carbon-based reduction.
-So, the answers will be:
(C) Aluminium from $A{l_2}{O_3}$
(D) Magnesium from $MgC{O_3}.CaC{O_3}$
So, the correct answer is “Option C and D”.

Note: The smelting process is used mainly for the extraction of silver (Ag), copper (Cu), iron (Fe) and other base metals. Carbon has the ability to reduce these metal ores by extracting oxygen from it because the oxygen present in the ore binds to carbon at high temperatures. This occurs because of the lower potential energies of the bonds in a $C{O_2}$ molecule.