Roasting and Calcination Questions in English

(A) The main function of roasting is to remove volatile impurities from the ore by heating it in a regular supply of air in a furnace at a temperature below the melting point of the metal.
Examples of removal of volatile substances:
$S_8 + 8O_2 \to 8SO_2 \uparrow$
$P_4 + 5O_2 \to P_4O_{10} \uparrow$
$4As + 3O_2 \to 2As_2O_3 \uparrow$

(C) Roasting is a metallurgical process in which sulphide ores are heated in a regular supply of air at a temperature below the melting point of the metal.
In this process,the sulphide ore is converted into its corresponding oxide.
For example: $2ZnS + 3O_2 \to 2ZnO + 2SO_2 \uparrow$

(A) In roasting,the ore is heated in a regular supply of air at a temperature below the melting point of the metal.
This process is generally applied to sulphide ores.
During roasting,the sulphide is converted into an oxide,and sulphur is removed as $SO_2$ gas.

(A) . $CaCO_3 \to CaO + CO_2$
Heating the ore in the absence of air is known as calcination.

(D) The process of heating an ore below its melting point in the presence of excess air to bring about chemical changes is known as $Roasting$. $Calcination$ is the process of heating an ore in the absence or limited supply of air.

(B) The process of heating the ore strongly in excess of air so that the volatile impurities are removed and the ore is changed to oxide is known as $Roasting$.

(D) Calcination is a process of heating an ore in a limited supply of air or in the absence of air.
Its primary roles include:
$1$. To remove volatile impurities and moisture.
$2$. To decompose carbonates into oxides (e.g.,$CaCO_3 \rightarrow CaO + CO_2$).
$3$. To drive off organic matter.
Therefore,all the mentioned options are correct.

(B) Calcination is a process of heating an ore strongly in a limited supply of air or in the absence of air.
This process is primarily used to convert carbonate ores into oxides (e.g.,$ZnCO_3 \rightarrow ZnO + CO_2$) or to remove moisture and volatile impurities.

(B) reverberatory furnace is designed such that the fuel does not come into direct contact with the ore. It is primarily used for the roasting and smelting of sulphide ores,where the ore is heated in the presence of air to convert it into its oxide or to remove volatile impurities.

(D) The correct answer is $(D)$.
Roasting is a process of heating a sulphide ore in the presence of excess air to convert it into its oxide form.
The given reaction $2ZnS + 3O_2 \to 2ZnO + 2SO_2$ represents the oxidation of zinc sulphide $(ZnS)$ to zinc oxide $(ZnO)$ using oxygen,which is the definition of roasting.

(B) Calcination is a process in which an ore is heated strongly in the absence or limited supply of air.
This process is primarily used to remove volatile impurities such as moisture $(H_2O)$ and carbon dioxide $(CO_2)$ from carbonate or hydrated ores.
For example: $ZnCO_3 \xrightarrow{\Delta} ZnO + CO_2$.

(B) Roasting is a process in which the concentrated ore is heated in a blast of air,converting the ore into oxides and oxidizing impurities like sulphur,arsenic,and antimony into their volatile oxides,which are then removed.
For copper pyrites $(CuFeS_2)$,roasting is controlled to remove excess sulphur while retaining enough to form $Cu_2S$ and $FeS$ for the subsequent smelting process.
The reactions are:
$2CuFeS_2 + O_2 \rightarrow Cu_2S + 2FeS + SO_2$
$2FeS + 3O_2 \rightarrow 2FeO + 2SO_2$
$2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$

(C) Roasting is a metallurgical process in which an ore is heated in a regular supply of air in a furnace at a temperature below the melting point of the metal.
It involves the volatilisation of volatile impurities,decomposition of the ore (e.g.,carbonates to oxides),and oxidation of the ore (e.g.,sulfides to oxides).

(B) The correct answer is $(B)$.
Roasting is a process of heating a sulphide ore in the presence of excess air to convert it into its metal oxide.
Zinc blende $(ZnS)$ is a sulphide ore,which undergoes roasting as follows:
$2ZnS + 3O_2 \xrightarrow{\Delta} 2ZnO + 2SO_2$

(C) The correct answer is $(C)$.
When cinnabar $(HgS)$ ore is roasted in the presence of air,it undergoes self-reduction to form mercury metal:
$HgS + O_2 \xrightarrow{\Delta} Hg + SO_2$
At the roasting temperature $(773 - 873 \ K)$,mercury exists as a vapor. These vapors are then condensed to obtain liquid mercury,which is approximately $99.7 \%$ pure.

(B) $($ $b$ $)$ In the roasting process,the ore (usually sulphide) is heated in the presence of excess air to convert it into its oxide form.

(A) Roasting is the process of heating the ore strongly in the presence of excess air. It is generally carried out in a reverberatory furnace or a blast furnace. Since a reverberatory furnace is not listed,and blast furnaces are commonly used for roasting sulfide ores,the most appropriate answer among the choices is $A$.

(B) Roasting is a metallurgical process in which an ore is heated in the presence of excess air at a temperature below its melting point.
This process is primarily used for sulphide ores to remove sulphur as volatile $SO_2$ gas.
The chemical reaction involved is: $S + O_2 \to SO_2$.

(A) The extraction of metal from carbonate ore involves heating the ore in the absence of air to convert it into its oxide form. This process is known as Calcination.
For example,for zinc carbonate: $ZnCO_3 \xrightarrow{\Delta} ZnO + CO_2$.
Therefore,the correct option is $A$.

(D) When cinnabar $(HgS)$ is heated strongly in air,it undergoes roasting to form mercury metal and sulphur dioxide gas.
The chemical reaction is: $HgS(s) + O_2(g) \xrightarrow{\Delta} Hg(l) + SO_2(g)$.
Other metal sulphides like $Cu_2S$ or $Fe_2S_3$ typically form metal oxides upon roasting rather than the pure metal.

(A) The process of heating an ore in the presence of excess air to a temperature below its melting point is known as $Roasting$.
This process is typically used for sulfide ores to convert them into their corresponding oxides.

(B) Zinc blende is $ZnS$.
First,$ZnS$ is roasted in the presence of air to form zinc oxide: $2ZnS + 3O_2 \rightarrow 2ZnO + 2SO_2$.
Then,the zinc oxide is reduced to zinc metal using carbon (coke) as a reducing agent: $ZnO + C \rightarrow Zn + CO$.

(A) $1$. Calcination is the process of heating an ore in the absence of air to remove moisture and volatile impurities. The reaction $Fe_2O_3 \cdot nH_2O \rightarrow Fe_2O_3 + nH_2O$ represents the removal of water of hydration,which is a calcination process $(I-a)$.
$2$. Roasting is the process of heating a sulphide ore in the presence of excess air. The reaction $2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$ is a classic example of roasting $(II-b)$.
$3$. Flux is a substance added to remove gangue. $SiO_2$ acts as an acidic flux to remove $FeO$ (basic gangue) to form slag $FeSiO_3$ $(III-c)$.
$4$. Thermite process involves the reduction of metal oxides using aluminum powder. The reaction $Cr_2O_3 + 2Al \rightarrow Al_2O_3 + 2Cr$ is a thermite reaction $(IV-d)$.
Therefore,the correct matching is $I-a, II-b, III-c, IV-d$.

(A) In the blast furnace,limestone $(CaCO_3)$ decomposes to form calcium oxide $(CaO)$ and carbon dioxide $(CO_2)$.
$CaCO_3 \rightarrow CaO + CO_2$
Here,$CaO$ acts as a flux which reacts with the silica $(SiO_2)$ impurity present in the ore to form calcium silicate $(CaSiO_3)$,which is known as slag.
$CaO + SiO_2 \rightarrow CaSiO_3$ (Slag)
Thus,limestone acts as a flux.

(B) Roasting is the process of heating a sulfide ore in the presence of excess air to convert it into its oxide.
For zinc blende $(ZnS)$,the chemical reaction is:
$2ZnS + 3O_2 \rightarrow 2ZnO + 2SO_2$
Thus,the products formed are zinc oxide $(ZnO)$ and sulfur dioxide $(SO_2)$.

(C) Calcination is a process of heating an ore strongly in a limited supply or absence of air. This process is typically used for carbonate or hydrated ores to remove moisture and volatile impurities,and to convert the ore into its oxide form. For example: $CaCO_3 \xrightarrow{\Delta} CaO + CO_2$.

(D) Calcination is a process of heating an ore strongly in a limited supply or absence of air.
It is primarily used for carbonate or hydrated ores.
In the reaction $MgCO_3 \rightarrow MgO + CO_2$,magnesium carbonate is heated to release carbon dioxide,which is a classic example of calcination.
Option $A$ is an oxidation reaction,option $B$ is roasting (in the presence of excess air),and option $C$ is also roasting of sulphide ore.

(B) Calcination is a process of heating an ore strongly in a limited supply of air or in the absence of air.
It is primarily used to remove volatile impurities like moisture $(H_2O)$ and carbon dioxide $(CO_2)$ from carbonate ores.
For example: $ZnCO_3 \xrightarrow{\Delta} ZnO + CO_2 \uparrow$.

(D) Roasting is a metallurgical process in which a sulfide ore is heated in a regular supply of air at a temperature below the melting point of the metal.
In all the given reactions:
$2PbS + 3O_2 \rightarrow 2PbO + 2SO_2$
$2ZnS + 3O_2 \rightarrow 2ZnO + 2SO_2$
$2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$
Sulfide ores are converted into their respective metal oxides by heating in the presence of oxygen.
Therefore,all these reactions represent roasting.

(B) Calcination is a process of heating an ore in a limited supply of air or in the absence of air. It is typically used for carbonate and hydroxide ores.
$(a)$ Argentite $(Ag_2S)$ is a sulfide ore,which undergoes roasting.
$(b)$ Bauxite $(Al_2O_3 \cdot 2H_2O)$ is a hydrated oxide ore,which undergoes calcination to remove water.
$(c)$ Malachite $(CuCO_3 \cdot Cu(OH)_2)$ is a carbonate/hydroxide ore,which undergoes calcination.
$(d)$ Copper pyrite $(CuFeS_2)$ is a sulfide ore,which undergoes roasting.
Therefore,both bauxite $(b)$ and malachite $(c)$ undergo calcination.

(D) Roasting is a process of heating a sulfide ore in a regular supply of air in a furnace at a temperature below the melting point of the metal.
During roasting:
$1$. Sulfide ores are converted into oxides (e.g.,$2ZnS + 3O_2 \rightarrow 2ZnO + 2SO_2$).
$2$. Volatile impurities like arsenic $(As_2O_3)$ and sulfur $(SO_2)$ are removed as gases.
Therefore,both statement $A$ and statement $C$ are correct.
Since the question asks for the correct statement and $D$ is 'All of the above',$D$ is the most appropriate answer.

(B) The conversion of hydrated alumina $(Al_2O_3 \cdot xH_2O)$ into anhydrous alumina $(Al_2O_3)$ is achieved by heating the ore in the absence of air. This process is known as Calcination. The chemical reaction is: $Al_2O_3 \cdot xH_2O \xrightarrow{\Delta} Al_2O_3 + xH_2O$.

(C) Calcination is the process of heating an ore strongly in the absence of air or in a limited supply of air to remove volatile impurities or to convert carbonates into oxides.
In the reaction $MgCO_3 \xrightarrow{\Delta} MgO + CO_2$,the metal carbonate is heated to produce the metal oxide and carbon dioxide,which is the definition of calcination.
Option $A$ is oxidation,option $B$ is roasting,and option $D$ is not a standard metallurgical process.

(C) Calcination is a process of heating an ore in a limited supply of air or in the absence of air.
$(1)$ It removes moisture from the ore,which is $True$.
$(2)$ It decomposes carbonates into oxides and carbon dioxide (e.g.,$CaCO_3 \rightarrow CaO + CO_2$),which is $True$.
$(3)$ It removes volatile impurities (like organic matter or non-metallic impurities),which is $True$.
Therefore,all statements are $True$. The correct option is $TTT$.

(B) Calcination is a process of heating an ore strongly in the limited supply or absence of air. $CaCO_3 \xrightarrow{\Delta} CaO + CO_2$. Therefore,the correct option is $B$.

(A) In a blast furnace,the decomposition of limestone $(CaCO_3)$ into calcium oxide $(CaO)$ and carbon dioxide $(CO_2)$ is an endothermic reaction.
This reaction requires heat to proceed: $CaCO_3(s) \xrightarrow{\Delta} CaO(s) + CO_2(g)$.
The other reactions listed,such as the combustion of carbon $(C + O_2 \rightarrow CO_2)$ and the reduction of iron ore $(Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2)$,are exothermic.

(D) Roasting of sulphide ores involves heating them in the presence of excess air,which produces $SO_2$ gas as a byproduct.
The chemical reaction is: $2MS + 3O_2 \rightarrow 2MO + 2SO_2$.
$SO_2$ is a colourless gas with a choking smell of burnt sulphur.
It causes damage to respiratory organs and is a major contributor to acid rain.
Its aqueous solution is acidic $(H_2SO_3)$,it acts as a reducing agent,and the corresponding acid $(H_2SO_3)$ is unstable and has never been isolated in pure form.
Therefore,the gas $X$ is $SO_2$.

(D) The standard free energies of formation $(\Delta G_f^o)$ of most metal sulphides are greater than those of $CS_2$ and $H_2S$.
This means that carbon and hydrogen cannot effectively reduce metal sulphides to their respective metals.
However,the standard free energies of formation of metal oxides are significantly lower than those of $SO_2$.
Therefore,the oxidation of metal sulphides to metal oxides is thermodynamically favourable.
Thus,roasting the sulphide ore to an oxide before reduction is a necessary step in the extraction process.
Consequently,the statement that carbon and hydrogen are suitable reducing agents for metal sulphides is false.

(C) Calcium carbonate $(CaCO_3)$ on thermal decomposition undergoes calcination to produce calcium oxide $(CaO)$ and carbon dioxide $(CO_2)$.
$CaO$ is a metallic oxide,which is basic in nature.
$CO_2$ is a non-metallic oxide,which is acidic in nature.
The reaction is: $CaCO_3 \xrightarrow{\Delta} CaO + CO_2 \uparrow$.

(D) The reduction of metal sulphides by carbon is generally not spontaneous because the $\Delta G$ value for the reaction $MS + C \rightarrow M + CS_2$ is positive.
In contrast,the reduction of metal oxides by carbon is spontaneous because the $\Delta G$ value for $MO + C \rightarrow M + CO_2$ is negative.
This difference arises because $CO_2$ is thermodynamically much more stable than $CS_2$.
Therefore,the stability of the metal sulphide compared to the oxide and the relative stability of $CO_2$ versus $CS_2$ are significant factors.
The volatility of $CO_2$ compared to $CS_2$ is not a thermodynamic factor that determines the feasibility of the reduction process.

(D) In the roasting of $Cu_2S$,the reaction is $2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$,which evolves $SO_2$.
In the self-reduction process,$2Cu_2O + Cu_2S \rightarrow 6Cu + SO_2$,which also evolves $SO_2$.
In the partial roasting of $FeS$,the reaction is $2FeS + 3O_2 \rightarrow 2FeO + 2SO_2$,which evolves $SO_2$.
When partially roasted $FeS$ (containing $FeO$) is heated with silica $(SiO_2)$,the reaction is $FeO + SiO_2 \rightarrow FeSiO_3$ (slag formation). In this specific step,no $SO_2$ is evolved.

(C) Calcination is a metallurgical process in which an ore is heated strongly in the absence of air or in a limited supply of air.
This process is primarily used to convert carbonate ores into oxides (e.g.,$ZnCO_3 \rightarrow ZnO + CO_2$) and to remove volatile impurities or moisture.
Therefore,the correct condition is the absence of air.

(C) Roasting is a process of heating the ore in a regular supply of air in a furnace at a temperature below the melting point of the metal.
$(i)$ Sulphide ores are converted into oxides and sulphates: $2ZnS + 3O_2 \rightarrow 2ZnO + 2SO_2$ and $ZnS + 2O_2 \rightarrow ZnSO_4$.
$(ii)$ Water of hydration is removed during the heating process.
$(iii)$ Roasting is carried out below the melting point of the ore,so it does not melt the ore.
$(iv)$ Volatile impurities like arsenic and sulphur are removed as their respective oxides (e.g.,$As_2O_3$,$SO_2$).
Therefore,statements $(i), (ii),$ and $(iv)$ are correct.

(A) In the extraction of lead $(Pb)$ from galena $(PbS)$,the ore is first roasted to form lead oxide $(PbO)$: $2PbS + 3O_2 \to 2PbO + 2SO_2$.
Self-reduction occurs when the remaining $PbS$ reacts with the formed $PbO$: $PbS + 2PbO \to 3Pb + SO_2$.
Carbon reduction involves the reduction of $PbO$ using carbon or carbon monoxide: $PbO + C \to Pb + CO$ or $PbO + CO \to Pb + CO_2$.
However,the roasting reaction $(PbS + \frac{3}{2} O_2 \to PbO + SO_2)$ is the essential preliminary step that provides the $PbO$ required for both subsequent reduction processes.

(D) The reduction of metal sulphides is thermodynamically difficult because the enthalpy of formation of metal sulphides is less negative than that of metal oxides.
Conversely,the enthalpy of formation of $CO_2$ is more negative than that of $CS_2$,making carbon a suitable reducing agent for metal oxides but not for metal sulphides.
Therefore,sulphide ores are first converted into metal oxides by roasting,which are then easily reduced to the metal.

(B) The process of auto-reduction is used for the extraction of metals like $Cu$,$Hg$,and $Pb$ from their sulfide ores. In this process,the sulfide ore is partially roasted in air to convert a part of the sulfide into its oxide or sulfate. This oxide or sulfate then reacts with the remaining unroasted sulfide ore to produce the metal without the need for an external reducing agent. For example,in the case of $Cu_2S$,the reaction is: $2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$ followed by $2Cu_2O + Cu_2S \rightarrow 6Cu + SO_2$.

(C) Calcination is the process of heating an ore strongly below its melting point in the absence or limited supply of air.
It is primarily used to convert metal carbonates and hydroxides into their respective oxides.
For example:
$CaCO_3 \xrightarrow{\Delta} CaO + CO_2 \uparrow$
$CuCO_3 \cdot Cu(OH)_2 \xrightarrow{\Delta} 2CuO + H_2O \uparrow + CO_2 \uparrow$
Thus,the product obtained is a metal oxide.

(D) Calcination is a process of heating an ore to a high temperature,but below its melting point,in the absence of air or in a limited supply of air.
This process is primarily used to remove volatile impurities like moisture $(H_2O)$ and carbon dioxide $(CO_2)$ from carbonate ores.

(B) Calcination is the process of heating an ore in the absence or limited supply of air to remove moisture and volatile impurities.
Option $A$ represents the removal of water of crystallization (calcination).
Option $C$ represents the thermal decomposition of carbonate ore (calcination).
Option $D$ represents the thermal decomposition of dolomite (calcination).
Option $B$ involves the reaction of sulfide ore with oxygen,which is known as roasting.
Therefore,the reaction that does not define calcination is $B$.