Occurrence and Extraction of Metals Questions in English

(N/A) $(i)$ Mineral: Most elements occur in nature in a combined state as minerals. The chemical composition of minerals is fixed.
$(ii)$ Ore: Minerals from which metals can be extracted profitably are known as ores.
$(iii)$ Gangue: The impurities (sand,silt,soil,gravel,etc.) present in the ore are called gangue.

(A) Metals that are at the bottom of the reactivity series are least reactive and are found in nature in the free (native) state because they do not react easily with oxygen,moisture,or other chemicals in the atmosphere.
Examples of such metals include $Gold$ $(Au)$,$Silver$ $(Ag)$,and $Platinum$ $(Pt)$.

(B) The chemical process used for obtaining a metal from its oxide is reduction. In this process,metal oxides are reduced by using suitable reducing agents such as carbon or by highly reactive metals to displace the metals from their oxides.
For example,zinc oxide is reduced to metallic zinc by heating with carbon:
$ZnO_{(s)} + C_{(s)} \xrightarrow{\Delta} Zn_{(s)} + CO_{(g)}$
Manganese dioxide is reduced to manganese by treating it with aluminium powder. In this case,aluminium acts as a reducing agent and displaces manganese from its oxide:
$3MnO_{2(s)} + 4Al_{(s)} \to 3Mn_{(l)} + 2Al_2O_{3(s)} + \text{Heat}$
Oxides of highly reactive metals are reduced by electrolytic reduction.

(B) In the electrolytic refining of a metal $M$:
$1$. Anode: $A$ block of impure metal $M$ is used as the anode.
$2$. Cathode: $A$ thin strip of pure metal $M$ is used as the cathode.
$3$. Electrolyte: An aqueous solution of a soluble salt of the metal $M$ is used as the electrolyte.
During electrolysis,the pure metal from the anode dissolves into the electrolyte,and an equivalent amount of pure metal from the electrolyte deposits on the cathode.

(C) Metals that are very low in the reactivity series are found in their native (free) state in nature because they are highly unreactive.
$Au$ (Gold) and $Ag$ (Silver) are noble metals and are found in their native state.
$Cu$ (Copper) can be found in its native state,but it is more commonly found in combined states (like sulfides or oxides).
$Zn$ (Zinc) is moderately reactive and is always found in combined states (like $ZnS$ or $ZnO$).
Therefore,among the given options,$Au$ and $Ag$ are the metals that primarily exist in their native state.

(D) Electrolytic refining is a process used to purify metals that are obtained from their ores.
Many metals like $Cu$,$Zn$,$Sn$,$Ni$,$Ag$,and $Au$ are refined electrolytically.
In this process,the impure metal is made the anode and a thin strip of pure metal is made the cathode.
Highly reactive metals like $Na$,$K$,$Ca$,and $Mg$ are obtained by the electrolytic reduction of their molten chlorides or oxides,not by electrolytic refining of the impure metal.
Therefore,among the given options,$Cu$ and $Au$ are refined by electrolytic refining.
Thus,the correct pair is $(i)$ and $(ii)$.

(B) Highly reactive metals like sodium $(Na)$ and calcium $(Ca)$ are placed at the top of the reactivity series.
These metals have a very high affinity for oxygen and cannot be reduced by carbon or other common reducing agents.
Therefore,they are extracted from their ores (usually chlorides) by the process of electrolytic reduction in the molten state.
Sodium is obtained by the electrolysis of molten sodium chloride $(NaCl)$,and calcium is obtained by the electrolysis of molten calcium chloride $(CaCl_2)$.
Iron $(Fe)$ and copper $(Cu)$ are less reactive and are typically extracted by reduction with carbon or by other metallurgical processes.
Thus,the correct metals obtained by the electrolysis of their molten chlorides are $(i)$ and $(ii)$.

(D) In the electrolytic refining of metals like zinc,an impure metal rod is used as the anode and a pure metal strip is used as the cathode.
An electrolyte solution containing a salt of the metal (e.g.,zinc sulfate) is used.
When an electric current is passed through the electrolyte,the metal from the impure anode dissolves into the solution as metal ions $(Zn^{2+})$.
These metal ions then migrate towards the cathode,where they gain electrons and get reduced to form pure metal,which deposits on the cathode.
Therefore,during the electrolytic refining of zinc,pure zinc is deposited on the cathode.

(N/A) Anode: Impure silver rod.
Cathode: Pure silver strip.
$(b)$ Electrolyte: An aqueous solution of a silver salt,such as silver nitrate $(AgNO_{3})$ acidified with dilute nitric acid $(HNO_{3})$.
$(c)$ After passing an electric current,pure silver is deposited at the cathode.

(B) In the process of metal extraction,it is thermodynamically and chemically easier to reduce metal oxides to pure metal using reducing agents like carbon or through electrolytic reduction compared to reducing metal sulphides or carbonates directly. Therefore,sulphides are converted to oxides by roasting,and carbonates are converted to oxides by calcination before the final reduction step.

(N/A) Mercury is the only metal that exists as a liquid at room temperature. It is obtained from its sulphide ore,known as cinnabar $(HgS)$,by heating it in the presence of air (roasting).
The chemical reactions involved are as follows:
$1$. Heating cinnabar in air to form mercury$(II)$ oxide:
$2HgS + 3O_2 \xrightarrow{\text{Heat}} 2HgO + 2SO_2$
$2$. Further heating of mercury$(II)$ oxide to obtain mercury metal:
$2HgO \xrightarrow{\text{Heat}} 2Hg + O_2$

(N/A) It undergoes calcination. The chemical reaction is:
$ZnCO_{3} \xrightarrow{\text{Heat}} ZnO + CO_{2}$
$(b)$ It undergoes auto-reduction,forming copper metal and sulphur dioxide gas:
$2Cu_{2}O + Cu_{2}S \xrightarrow{\text{Heat}} 6Cu + SO_{2}$

(B) Carbonate and sulphide ores are usually converted into oxides during the process of extraction because it is thermodynamically and chemically easier to reduce metal oxides to pure metals using reducing agents like carbon or through electrolysis compared to reducing carbonates or sulphides directly. Metal oxides are more amenable to reduction processes.

(N/A) Roasting is the process of heating a sulphide ore in the presence of excess air. The reaction for zinc sulphide $(ZnS)$ is:
$2ZnS(s) + 3O_2(g) \xrightarrow{\text{Heat}} 2ZnO(s) + 2SO_2(g)$
$(b)$ Calcination is the process of heating a carbonate ore in the absence or limited supply of air. The reaction for zinc carbonate $(ZnCO_3)$ is:
$ZnCO_3(s) \xrightarrow{\text{Heat}} ZnO(s) + CO_2(g)$

(N/A) For metals of low reactivity:
Sulphide ore $\xrightarrow{\text{Roasting}}$ Metal $\xrightarrow{\text{Refining}}$ Pure metal
For metals of medium reactivity:
Sulphide ore $\xrightarrow{\text{Roasting}}$ Metal oxide $\xrightarrow{\text{Reduction}}$ Metal $\xrightarrow{\text{Refining}}$ Pure metal
$1$. Roasting: The sulphide ore is heated strongly in the presence of excess air to convert it into metal oxide (for medium reactivity) or directly into metal (for low reactivity).
$2$. Reduction: The metal oxide obtained is reduced to metal using a suitable reducing agent like carbon.
$3$. Refining: The crude metal obtained is purified through various methods like electrolytic refining.

(N/A) $(i)$ $(a)$ Roasting of sulphide ore:
$2Cu_2S(s) + 3O_2(g) \xrightarrow{\Delta} 2Cu_2O(s) + 2SO_2(g)$
$(b)$ Reduction of copper $(I)$ oxide:
$2Cu_2O(s) + Cu_2S(s) \xrightarrow{\Delta} 6Cu(s) + SO_2(g)$
This reaction is known as auto-reduction.
$(c)$ Reaction for electrolytic refining:
At cathode: $Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)$
At anode: $Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-$
$(ii)$ The diagram for the electrolytic refining of copper shows an electrolytic tank containing acidified copper sulphate solution,an impure copper anode,a pure copper cathode,and the collection of anode mud at the bottom.

(N/A) Since ore $A$ releases $CO_2$ upon heating, it is a carbonate ore. Carbonate ores are converted into metal oxides by the process of $Calcination$ (heating in limited supply of air).
$MCO_3 \xrightarrow{Calcination} MO + CO_2$
Then, the metal oxide is reduced to metal using a reducing agent like carbon:
$MO + C \xrightarrow{Reduction} M + CO$
Since ore $B$ releases $SO_2$ upon heating, it is a sulfide ore. Sulfide ores are converted into metal oxides by the process of $Roasting$ (heating in excess supply of air).
$2MS + 3O_2 \xrightarrow{Roasting} 2MO + 2SO_2$
Then, the metal oxide is reduced to metal using a reducing agent like carbon:
$MO + C \rightarrow M + CO$

(N/A) Highly reactive metals (such as $Na, Mg, Ca, Al$) have a much stronger affinity for oxygen than carbon does. Because their bond with oxygen is significantly more stable,carbon is unable to displace the metal from its oxide. Therefore,these metals are extracted from their ores by electrolytic reduction rather than carbon reduction.

(B) The extraction of metals from their sulphide and carbonate ores is difficult because these compounds are chemically stable and do not easily release the metal.
However,metal oxides are much easier to reduce to pure metal using reducing agents like carbon or through electrolytic reduction.
Therefore,sulphide ores are first converted into oxides by roasting (heating in the presence of excess air),and carbonate ores are converted into oxides by calcination (heating in the absence or limited supply of air).

(N/A)

Roasting	Calcination
$1.$ In this,the ore is heated in the presence of excess air.	$1.$ In this,the ore is heated in the absence or limited supply of air.
$2.$ It is primarily done for sulphide ores.	$2.$ It is primarily done for carbonate ores.
$3.$ $SO_2$ gas is evolved.	$3.$ $CO_2$ gas is evolved.
$4.$ Example: $2ZnS + 3O_2 \xrightarrow{\text{heat}} 2ZnO + 2SO_2$	$4.$ Example: $ZnCO_3 \xrightarrow{\text{heat}} ZnO + CO_2$

(N/A) The primary ore of mercury is $HgS$,known as Cinnabar.
Extraction process:
$1$. Roasting: The ore $HgS$ is first heated in the presence of excess air to convert it into mercuric oxide $(HgO)$.
$2HgS + 3O_2 \xrightarrow{\Delta} 2HgO + 2SO_2$
$2$. Reduction: Mercuric oxide $(HgO)$ is then reduced to metallic mercury $(Hg)$ by further heating,as it is unstable at high temperatures.
$2HgO \xrightarrow{\Delta} 2Hg + O_2$

(N/A) Copper is obtained from copper$(I)$ sulfide $(Cu_{2}S)$ through a process known as self-reduction or auto-reduction by heating it in the presence of air.
First,a portion of the copper$(I)$ sulfide is converted into copper$(I)$ oxide by heating it in air:
$2Cu_{2}S + 3O_{2} \xrightarrow{\Delta} 2Cu_{2}O + 2SO_{2}$
Then,the remaining copper$(I)$ sulfide reacts with the copper$(I)$ oxide formed to produce metallic copper:
$2Cu_{2}O + Cu_{2}S \xrightarrow{\Delta} 6Cu + SO_{2}$

(N/A) Sodium is a highly reactive metal with a very high affinity for oxygen. Carbon is a weaker reducing agent than sodium,so it cannot reduce sodium oxide to sodium metal.
$(b)$ Sodium is obtained from molten sodium chloride $(NaCl)$ by the process of electrolytic reduction (electrolysis). During this process,sodium ions $(Na^+)$ are reduced at the cathode to form metallic sodium $(Na)$.

(N/A) $(i)$ The insoluble impurities that settle down at the bottom of the anode during electrolytic refining are known as 'anode mud'. The cathode is made of a thin strip of pure metal.
$(ii)$ During the electrolytic refining of copper:
At anode: $Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-$
At cathode: $Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)$

(N/A) Two metals purified by electrolytic refining are $Copper$ $(Cu)$ and $Zinc$ $(Zn)$.
In the electrolytic refining process:
$1$. The $Anode$ is made of an impure block of the metal.
$2$. The $Cathode$ is made of a thin strip of pure metal.
$3$. The $Electrolyte$ is an aqueous solution of a salt of the metal being refined.
The pure metal is deposited on the $Cathode$.

(N/A) Carbonate ores are subjected to calcination.
Example: Zinc carbonate $(ZnCO_{3})$ is calcined to form zinc oxide $(ZnO)$.
$ZnCO_{3}(s) \xrightarrow{\text{Heat}} ZnO(s) + CO_{2}(g)$
$(b)$ The calcined ore is obtained in the form of a metal oxide. It can be reduced to the metal using a reducing agent like carbon (coke) or by electrolytic reduction.
For the example of zinc oxide $(ZnO)$:
$ZnO(s) + C(s) \rightarrow Zn(s) + CO(g)$
$(c)$ Two metals used as reducing agents are Aluminum $(Al)$ and Sodium $(Na)$.

(A) $(i)$ The metal $E$ is Sodium $(Na)$.
$(ii)$ Reaction with air: $4Na + O_{2} \rightarrow 2Na_{2}O$.
Reaction with water: $Na_{2}O + H_{2}O \rightarrow 2NaOH$.
$(iii)$ Sodium is obtained from molten sodium chloride $(NaCl)$ by the process of electrolytic reduction (electrolysis). In this process,an electric current is passed through the molten salt.
At cathode: $Na^{+} + e^{-} \rightarrow Na$ (Reduction).
At anode: $2Cl^{-} \rightarrow Cl_{2} + 2e^{-}$ (Oxidation).

(N/A) $(i)$ Extraction of copper from its sulphide ore $(Cu_2S)$:
$(a)$ Roasting: The sulphide ore is heated in the presence of excess air to convert it into copper$(I)$ oxide.
$2Cu_2S(s) + 3O_2(g) \xrightarrow{\text{heat}} 2Cu_2O(s) + 2SO_2(g)$
$(b)$ Reduction: The copper$(I)$ oxide is then heated with more copper$(I)$ sulphide to obtain copper metal.
$2Cu_2O(s) + Cu_2S(s) \xrightarrow{\text{heat}} 6Cu(s) + SO_2(g)$
$(ii)$ Refining of metals: It is the process of removing impurities from the crude metal obtained after reduction to get pure metal.
Electrolytic refining of copper:
Anode: Impure copper block.
Cathode: Pure copper strip.
Electrolyte: Acidified copper sulphate solution $(CuSO_4 + H_2SO_4)$.

(N/A)

Roasting	Calcination
Heating in the presence of excess air. Done for sulphide ores.	Heating in a limited supply of air. Done for carbonate ores.

$(b)$ $(i)$ Self-reduction: Less reactive metals like mercury $(Hg)$ or copper $(Cu)$ can be reduced by heating alone.
$2HgO \xrightarrow{\text{heat}} 2Hg + O_2$
$2Cu_2O + Cu_2S \xrightarrow{\text{heat}} 6Cu + SO_2$
$(ii)$ Reduction using carbon or displacement: Moderately reactive metals are reduced by heating with carbon or using highly reactive metals like aluminum $(Al)$ in thermite reactions.
$ZnO + C \rightarrow Zn + CO$
$Fe_2O_3 + 2Al \rightarrow 2Fe + Al_2O_3 + \text{Heat}$
$(iii)$ Electrolytic reduction: Highly reactive metals (e.g.,$Na, Mg, Ca$) are extracted by the electrolysis of their molten chlorides because they have a high affinity for oxygen.

(N/A) $(i)$

Electrolytic reduction	Electrolytic refining
It is a process of obtaining metals from their molten chlorides or oxides by electrolysis. The metals are deposited at the cathode,whereas chlorine or oxygen is liberated at the anode.	It is a process of refining impure metals obtained by any reduction process. The impure metal is taken as the anode,pure metal as the cathode,and a metal salt solution as the electrolyte.

$(ii)$ Minerals are naturally occurring elements or compounds in the Earth's crust. Ores are those minerals from which metals can be extracted profitably and conveniently.
$(iii)$ An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal. An amalgam is a specific type of alloy in which one of the components is mercury $(Hg)$.

(A) Ores are naturally occurring minerals from which metals can be extracted profitably.
These ores are usually contaminated with earthy impurities such as soil,sand,and rocky materials.
These unwanted impurities present in the ore are collectively known as $Gangue$.

(B) Highly reactive metals such as Sodium $(Na)$ and Calcium $(Ca)$ are placed at the top of the reactivity series.
These metals have a very high affinity for oxygen and cannot be reduced by carbon or other common reducing agents.
Therefore,they are extracted by the electrolytic reduction of their molten chloride salts (e.g.,$NaCl$ and $CaCl_2$).
Metals like Iron $(Fe)$ and Copper $(Cu)$ are less reactive and are typically extracted by reduction with carbon or other chemical methods.
Thus,only $(i)$ and $(ii)$ are obtained by the electrolysis of their molten chlorides.

(A) In the process of electrolytic refining of metals like zinc,an impure metal rod is used as the anode and a thin strip of pure metal is used as the cathode.
When an electric current is passed through the electrolyte (a salt solution of the metal),the impure metal from the anode dissolves into the electrolyte.
Simultaneously,an equivalent amount of pure metal from the electrolyte is deposited on the cathode.
Therefore,during the electrolytic refining of zinc,pure zinc gets deposited on the cathode.

(C) Metals that are very low in the reactivity series are found in their native (free) state in nature because they are highly unreactive.
These metals include gold $(Au)$,silver $(Ag)$,and platinum $(Pt)$.
In the given list:
$(i)$ $Au$ (Gold) is a noble metal and exists in a native state.
$(ii)$ $Cu$ (Copper) is found in both native and combined states (as sulfides or oxides).
$(iii)$ $Ag$ (Silver) is a noble metal and exists in a native state.
$(iv)$ $Fe$ (Iron) is highly reactive and is always found in a combined state (as oxides,carbonates,or sulfides).
Therefore,$(i)$ and $(iii)$ are the correct metals that exist in their native state.

(A) Electrolytic refining is a process used to purify metals that are obtained from their ores.
Metals like copper $(Cu)$,gold $(Au)$,silver $(Ag)$,and zinc $(Zn)$ are commonly refined using the electrolytic refining method.
In this process,an impure metal is made the anode,and a pure strip of the same metal is made the cathode.
Metals like sodium $(Na)$ and potassium $(K)$ are highly reactive and are extracted by the electrolytic reduction of their molten chlorides,not by electrolytic refining of the metal itself.
Therefore,$(i)$ $Au$ and $(ii)$ $Cu$ are the metals refined by electrolytic refining.

(TRUE) The statement is True.
Minerals are naturally occurring inorganic substances found in the earth's crust. They have a definite chemical composition and a crystalline structure. Elements or compounds that occur naturally in the earth's crust are indeed defined as minerals.

(TRUE) True.
An ore is a type of rock that contains sufficient minerals with important elements,including metals,that can be economically extracted from the rock.
While all ores are minerals,not all minerals are ores,because some minerals may contain a metal but it may not be profitable or feasible to extract it.

(A) Alumina is the common name for aluminum oxide.
Its chemical formula is $Al_{2}O_{3}$.
It is a naturally occurring oxide of aluminum and is the primary ore of aluminum, known as bauxite when impure.

(B) Roasting is a metallurgical process in which a sulfide ore is heated strongly in the presence of excess air to convert it into its oxide form.
In the reaction $2ZnS_{(s)} + 3O_{2(g)} \xrightarrow{\Delta} 2ZnO_{(s)} + 2SO_{2(g)}$,zinc sulfide $(ZnS)$ is heated in the presence of oxygen to form zinc oxide $(ZnO)$ and sulfur dioxide $(SO_2)$.
Therefore,this reaction represents roasting.
Option $A$ represents calcination (heating carbonate ore in limited air).
Option $C$ represents reduction of metal oxide using carbon.
Option $D$ represents the reaction of metal with steam.

(B) The process of obtaining a metal from its metal oxide is known as reduction.
Metal oxides are compounds where metal is in an oxidized state.
To extract the pure metal,oxygen must be removed from the metal oxide.
This removal of oxygen is chemically defined as reduction.
Common reducing agents like carbon (coke),carbon monoxide,or more reactive metals (like aluminum in the thermite process) are used to perform this reduction.

(B) The Earth's crust is the largest source of metals. Many metals are found in the Earth's crust in the form of minerals.
Most of the metals are found in the form of oxides or sulphides because these are the most stable forms of metals in the presence of oxygen and sulphur in the Earth's crust.
Therefore,the correct answer is $B$.

(C) Metals that are at the bottom of the reactivity series are the least reactive.
These metals are often found in a free or native state in nature because they do not react easily with oxygen,moisture,or other substances in the environment.
Gold $(Au)$,silver $(Ag)$,and platinum $(Pt)$ are examples of such metals.
Iron $(Fe)$,Aluminum $(Al)$,and Calcium $(Ca)$ are more reactive and are typically found in the form of oxides,sulfides,or carbonates (ores).

(B) Copper pyrites,also known as chalcopyrite,is the most important ore of copper.
Its chemical formula is $CuFeS_{2}$.
- $Cu_{2}S$ is Chalcocite.
- $Cu_{2}O$ is Cuprite.
- $Cu(OH)_{2} \cdot CuCO_{3}$ is Malachite.

(D) The primary ore of aluminium is $Bauxite$ $(Al_2O_3 \cdot 2H_2O)$.
$Siderite$ is an ore of iron $(FeCO_3)$.
$Horn \text{ } silver$ is an ore of silver $(AgCl)$.
$Cuprite$ is an ore of copper $(Cu_2O)$.
Therefore, the correct option is $D$.

(A) Bauxite is the primary ore of aluminum.
Its chemical composition is primarily hydrated aluminum oxide.
The general chemical formula for bauxite is $Al_{2}O_{3} \cdot 2H_{2}O$ (or sometimes represented as $Al_{2}O_{3} \cdot nH_{2}O$ where $n$ is between $1$ and $3$).
Therefore,the correct option is $A$.

(B) Malachite is a green-colored carbonate mineral with the chemical formula $Cu_2CO_3(OH)_2$.
It is a significant ore of the metal Copper $(Cu)$.
Therefore,the correct option is $B$.

(C) Dolomite is a sedimentary carbonate rock that contains a high proportion of the mineral dolomite,$CaMg(CO_3)_2$.
It is primarily considered an important source of $Calcium$ and $Magnesium$.
Among the given options,$Calcium$ is the correct metal associated with dolomite.

(D) The chemical formulas for the given ores are:
$1$. Dolomite: $CaCO_3 \cdot MgCO_3$ (Carbonate ore)
$2$. Siderite: $FeCO_3$ (Carbonate ore)
$3$. Horn silver: $AgCl$ (Halide ore)
$4$. Bauxite: $Al_2O_3 \cdot 2H_2O$ (Oxide ore)
Since Bauxite contains aluminum oxide, it is classified as an oxide ore. Therefore, the correct option is $D$.

(A) The chemical formula for Copper glance is $Cu_2S$,which is a sulphide ore.
Cuprite is $Cu_2O$ (oxide ore).
Haematite is $Fe_2O_3$ (oxide ore).
Malachite is $Cu(OH)_2 \cdot CuCO_3$ (carbonate/hydroxide ore).
Therefore,the correct option is $A$.

(B) The chemical formula for Siderite is $FeCO_3$, which is an iron carbonate ore.
Bauxite is an oxide ore of aluminum $(Al_2O_3 \cdot 2H_2O)$.
Copper pyrites is a sulfide ore of copper $(CuFeS_2)$.
Cuprite is an oxide ore of copper $(Cu_2O)$.
Therefore, Siderite is the correct answer as it is a carbonate ore.