Mix Examples - Metals and Non-metals Questions in English

(B) Based on the displacement reactions:
$1$. $B$ displaces iron,copper,and silver,but not zinc. Thus,$B$ is more reactive than iron,copper,and silver,but less reactive than zinc.
$2$. $A$ displaces copper and silver,but not iron or zinc. Thus,$A$ is more reactive than copper and silver,but less reactive than iron.
$3$. $C$ displaces only silver. Thus,$C$ is more reactive than silver,but less reactive than iron,copper,and zinc.
$4$. $D$ does not displace any of the metals. Thus,$D$ is the least reactive.
$(i)$ The most reactive metal is $B$.
$(ii)$ If $B$ is added to a solution of Copper $(II)$ sulphate,$B$ will displace copper from the solution,resulting in a color change (typically the blue solution turns colorless or pale green depending on the metal salt formed).
$(iii)$ The order of decreasing reactivity is $B > A > C > D$.

(D) displacement reaction occurs when a more reactive metal displaces a less reactive metal from its oxide. Based on the reactivity series $(Mg > Zn > Cu)$:

Metal	Zinc $(Zn)$	Magnesium $(Mg)$	Copper $(Cu)$
Zinc oxide $(ZnO)$	No reaction	Displacement	No reaction
Magnesium oxide $(MgO)$	No reaction	No reaction	No reaction
Copper oxide $(CuO)$	Displacement	Displacement	No reaction

Displacement reactions occur when:
$1$. $Mg$ is heated with $ZnO$ $(Mg + ZnO \rightarrow MgO + Zn)$
$2$. $Zn$ is heated with $CuO$ $(Zn + CuO \rightarrow ZnO + Cu)$
$3$. $Mg$ is heated with $CuO$ $(Mg + CuO \rightarrow MgO + Cu)$

(A) Zinc,being more reactive than copper,displaces copper from its solution,and a solution of zinc sulphate is obtained.
$Zn(s) + CuSO_4(aq) \rightarrow ZnSO_4(aq) + Cu(s)$
This is an example of a displacement reaction.
$(b)$ Aluminium,being more reactive,displaces hydrogen from dilute hydrochloric acid solution,and hydrogen gas is evolved.
$2Al(s) + 6HCl(aq) \rightarrow 2AlCl_3(aq) + 3H_2(g)$
$(c)$ Silver metal,being less reactive than copper,cannot displace copper from its salt solution. Therefore,no reaction occurs.
$Ag(s) + CuSO_4(aq) \rightarrow \text{No reaction}$

(A) The mixture of concentrated $HCl$ and concentrated $HNO_3$ in a $3:1$ ratio is known as Aqua regia.
Aqua regia is a highly corrosive,fuming liquid that is capable of dissolving noble metals like gold $(Au)$ and platinum $(Pt)$.
In the given scenario,the metal did not react with individual acids in test tubes $A$ and $B$ but dissolved in the mixture in test tube $C$.
Since gold $(Au)$ is a noble metal that does not react with concentrated $HCl$ or $HNO_3$ individually but dissolves in Aqua regia,the metal is gold $(Au)$.

(B) An alloy is a homogeneous mixture of two or more metals,or a metal and a non-metal.
It is prepared by first melting the primary metal and then dissolving the other elements in it in definite proportions.
Since the components are uniformly distributed throughout the mixture,it is classified as a homogeneous mixture.

(B) An alloy is a homogeneous mixture of two or more metals,or a metal and a non-metal.
$1$. Brass is an alloy of copper $(Cu)$ and zinc $(Zn)$,both of which are metals.
$2$. Steel is an alloy of iron $(Fe)$ and carbon $(C)$. Carbon is a non-metal.
$3$. Amalgam is an alloy of mercury $(Hg)$ with another metal.
$4$. Bronze is an alloy of copper $(Cu)$ and tin $(Sn)$,both of which are metals.
Therefore,steel is the alloy that contains a non-metal (carbon) as one of its constituents.

(A) In the process of electrolytic refining of copper:
$1$. An impure copper rod is used as the anode (connected to the positive terminal of the battery).
$2$. $A$ thin strip of pure copper is used as the cathode (connected to the negative terminal of the battery).
$3$. An acidified copper sulfate $(CuSO_4)$ solution is used as the electrolyte.
$4$. On passing electric current,pure copper from the anode dissolves into the electrolyte,and an equivalent amount of pure copper from the electrolyte deposits on the cathode.
$5$. The impurities from the anode settle down at the bottom of the tank as 'anode mud'.
$6$. Figure $A$ correctly depicts this setup with the anode connected to the positive terminal and the cathode to the negative terminal.

(N/A) Solder is an alloy composed of lead $(Pb)$ and tin $(Sn)$.
The primary property that makes solder suitable for welding electrical wires is its low melting point,which allows it to melt easily at relatively low temperatures without damaging the delicate electrical components.

(A) The soft and reactive metal is Sodium $(Na)$ or Potassium $(K)$.
$(b)$ The metal that is an important constituent of limestone $(CaCO_3)$ is Calcium $(Ca)$.
$(c)$ The metal that exists in a liquid state at room temperature is Mercury $(Hg)$.
Reactivity series order: $Hg < Ca < Na < K$.

(B) Non-metals typically form acidic oxides when they react with oxygen. Since the oxide $A_{2}O_{3}$ is acidic in nature,the element $A$ must be a non-metal.

$(A) A = N_2$ (Nitrogen), $B = NH_3$ (Ammonia), $C = NO$ (Nitric oxide), $D = HNO_3$ (Nitric acid).
Step $1$: Nitrogen $(N_2)$ is the most abundant gas in the atmosphere.
Step $2$: Haber's process: $N_2 + 3H_2 \xrightarrow{Fe} 2NH_3$ (Gas $B$).
Step $3$: Catalytic oxidation: $N_2 + O_2 \rightarrow 2NO$ (Oxide $C$).
Step $4$: Formation of acid: $4NO + 3O_2 + 2H_2O \rightarrow 4HNO_3$ (Acid $D$).
$(b)$ Nitrogen $(N_2)$ belongs to Group $15$ of the Periodic Table.

(N/A) When $Al$ is dipped in $HNO_3$,a thin,protective,and non-reactive layer of aluminum oxide $(Al_2O_3)$ forms on its surface. This layer prevents further reaction of the metal with the acid,thereby decreasing its reactivity.
$(b)$ $Na$ and $Mg$ are highly reactive metals that have a much stronger affinity for oxygen than carbon does. Therefore,carbon cannot displace oxygen from $Na_2O$ or $MgO$ to reduce them to their respective metals.

(A) In solid $NaCl$,the movement of ions is not possible due to its rigid structure. However,in aqueous solution or molten state,the electrostatic forces of attraction are overcome,allowing the ions to move freely and conduct electricity.
$(b)$ Iron articles are galvanised to protect them from corrosion (rusting). Galvanisation involves coating iron with a thin layer of zinc,which is more reactive than iron and prevents the iron from coming into contact with oxygen and moisture.
$(c)$ Metals like $Na, K, Ca$ and $Mg$ are highly reactive. They readily react with other elements such as oxygen,sulfur,and carbon present in the environment to form compounds like oxides,sulfides,or carbonates,and therefore are never found in their free elemental state in nature.

(A) $A = Na$ (Sodium),$B = Cl_2$ (Chlorine),$C = NaCl$ (Sodium chloride),$D = NaOH$ (Sodium hydroxide).
$1$. Reaction of $A$ with $B$: $2Na(s) + Cl_2(g) \rightarrow 2NaCl(s)$.
$2$. Electrolysis of aqueous solution of $C$ (Chlor-alkali process): $2NaCl(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + Cl_2(g) + H_2(g)$.

(B) is the most reactive element.
Reason: $B$ displaces both $A$ and $C$ from their respective compounds,which indicates that $B$ has a higher reactivity than both $A$ and $C$.
$(b)$ $C$ is the least reactive element.
Reason: $C$ is displaced by both $A$ and $B$ in the given chemical reactions,which indicates that $C$ has the lowest reactivity among the three.
$(c)$ These are displacement reactions.
Reason: In each reaction,a more reactive element displaces a less reactive element from its compound.

(C) Silver $(Ag)$ is less reactive than copper $(Cu)$ according to the reactivity series of metals.
Therefore,silver cannot displace copper from its salt solution $(CuSO_4)$.
Since no reaction occurs,there is no chemical equation to write.

(N/A) $Zn(s) + H_{2}SO_{4}(aq) \rightarrow ZnSO_{4}(aq) + H_{2}(g)$
$(b)$ $Zn(s) + 2HCl(aq) \rightarrow ZnCl_{2}(aq) + H_{2}(g)$
$(c)$ $3Zn(s) + 2AlCl_{3}(aq) \rightarrow 3ZnCl_{2}(aq) + 2Al(s)$ (Zinc is more reactive than Aluminium,so it displaces it)
$(d)$ $Zn(s) + 2NaOH(aq) \rightarrow Na_{2}ZnO_{2}(aq) + H_{2}(g)$ (Formation of Sodium zincate)
$(e)$ $4Zn(s) + 10HNO_{3}(dilute) \rightarrow 4Zn(NO_{3})_{2}(aq) + NH_{4}NO_{3}(aq) + 3H_{2}O(l)$

(N/A) $(i)$ Metals contain free electrons that can move throughout the metallic lattice,allowing them to conduct electricity.
$(ii)$ Non-metals are electron acceptors. To displace hydrogen from dilute acids,electrons must be supplied to the $H^+$ ions of the acid. Since non-metals cannot donate electrons,they cannot displace hydrogen.
$(iii)$ Aluminium reacts with oxygen to form a thin,protective layer of aluminium oxide $(Al_2O_3)$ on its surface. This layer is non-reactive and prevents further oxidation of the underlying metal,making it suitable for kitchen utensils.

(N/A) The element found in bones is Calcium $(Ca)$. The oxide of this metal used in the cement industry is Calcium oxide $(CaO)$,also known as quicklime.
When $CaO$ reacts with water,it forms Calcium hydroxide $(Ca(OH)_2)$,which is basic in nature and turns red litmus blue.
The chemical reaction is: $CaO(s) + H_2O(l) \rightarrow Ca(OH)_2(aq)$.
$(b)$ Among the given metals,Magnesium $(Mg)$ reacts only with hot water.
The products formed are Magnesium hydroxide $(Mg(OH)_2)$ and Hydrogen gas $(H_2)$.
The chemical reaction is: $Mg(s) + 2H_2O(l) \rightarrow Mg(OH)_2(aq) + H_2(g)$.

(N/A) $(i)$ $3Fe(s) + 4H_2O(g) \rightarrow Fe_3O_4(s) + 4H_2(g)$
$(ii)$ $Mg(s) + 2HCl(aq) \rightarrow MgCl_2(aq) + H_2(g)$
$(iii)$ $2Cu(s) + O_2(g) \xrightarrow{\Delta} 2CuO(s)$

(N/A) $(i)$ Sodium $(Na)$ and potassium $(K)$ are highly reactive metals that react vigorously with moisture and oxygen in the air,so they are stored in kerosene to prevent reaction.
$(ii)$ Nickel $(Ni)$ and chromium $(Cr)$ are added to iron $(Fe)$ to produce stainless steel,which is resistant to corrosion.
$(iii)$ Gold $(Au)$ and silver $(Ag)$ are the most malleable and ductile metals,allowing them to be beaten into thin sheets and drawn into thin wires.

(N/A) $(i)$ Iron does not burn in air even on strong heating. At high temperature,it combines with oxygen of the air to form $Fe_{3}O_{4}$.
$3Fe(s) + 2O_{2}(g) \xrightarrow{\text{Heat}} Fe_{3}O_{4}(s)$
$(ii)$ Calcination of lead carbonate involves heating the ore in the absence of air.
$PbCO_{3}(s) \xrightarrow{\text{Heat}} PbO(s) + CO_{2}(g)$
$(iii)$ This is a thermite reaction where aluminium acts as a reducing agent.
$Cr_{2}O_{3}(s) + 2Al(s) \rightarrow Al_{2}O_{3}(s) + 2Cr(l) + \text{Heat}$

(N/A) $(i)$ The order of decreasing reactivity is: Sodium > Aluminium > Copper > Gold.
$(ii)$ When aluminium powder is heated with manganese dioxide, a thermite reaction occurs, producing manganese metal and aluminium oxide: $4Al(s) + 3MnO_2(s) \xrightarrow{\Delta} 3Mn(l) + 2Al_2O_3(s) + \text{Heat}$.

(N/A) $(i)$ Mercury $(Hg)$ is a metal that does not stick to glass due to its high surface tension and weak adhesive forces with glass.
$(ii)$ Aluminium $(Al)$ is the metal commonly used in thermite welding because it acts as a strong reducing agent when reacting with metal oxides.
$(iii)$ Zinc oxide $(ZnO)$ is amphoteric in nature,meaning it reacts with both acids and bases to form salt and water.

(N/A) Magnesium reacts with very dilute nitric acid to produce magnesium nitrate and hydrogen gas:
$Mg(s) + 2HNO_3(aq) \longrightarrow Mg(NO_3)_2(aq) + H_2(g)$
$(b)$ Aluminium powder reacts with iron$(III)$ oxide in a thermite reaction to produce iron and aluminium oxide:
$Fe_2O_3(s) + 2Al(s) \longrightarrow 2Fe(l) + Al_2O_3(s) + \text{Heat}$
$(c)$ Zinc sulphide is roasted in the presence of oxygen to produce zinc oxide and sulphur dioxide gas:
$2ZnS(s) + 3O_2(g) \xrightarrow{\Delta} 2ZnO(s) + 2SO_2(g)$

(N/A) Aluminium forms a strong,non-porous,and protective layer of aluminium oxide $(Al_2O_3)$ on its surface upon exposure to air. This layer does not peel off easily and prevents further oxidation or corrosion of the underlying metal.
$(b)$ Dilute $HNO_3$ is a strong oxidising agent. When it reacts with metals like zinc,it oxidises the hydrogen gas produced during the reaction into water $(H_2O)$ and itself gets reduced to nitrogen oxides (such as $N_2O$,$NO$,or $NO_2$).
$(c)$ Aluminium has a much higher affinity for oxygen than carbon does. Therefore,carbon cannot effectively remove oxygen from aluminium oxide $(Al_2O_3)$ to produce aluminium metal. Consequently,electrolytic reduction is used instead of carbon reduction.

(A) Calcium starts floating when added to water because the bubbles of hydrogen gas formed during the reaction stick to the surface of the metal,making it buoyant.
$(b)$ Nitric acid $(HNO_{3})$ is a strong oxidizing agent. When it reacts with metals,it oxidizes the hydrogen gas produced to water $(H_{2}O)$ and itself gets reduced to nitrogen oxides $(N_{2}O, NO, NO_{2})$.
$(c)$ The chemical equation is: $3Fe(s) + 4H_{2}O(g) \rightarrow Fe_{3}O_{4}(s) + 4H_{2}(g)$.
The compound obtained is iron($II$,$III$) oxide,also known as ferroferric oxide $(Fe_{3}O_{4})$.

(A) Since the ore releases $SO_2$ gas upon heating in air,it is a sulphide ore.
The steps of metallurgy are as follows:
$(i)$ Concentration of ore: Usually done by the froth floatation process for sulphide ores.
$(ii)$ Roasting: The concentrated sulphide ore is heated strongly in the presence of excess air to convert it into metal oxide.
$(iii)$ Reduction: The metal oxide is reduced to the metal by heating with a reducing agent like carbon or by self-reduction.
$(b)$ $(i)$ $Zn(s) + CuSO_4(aq) \rightarrow ZnSO_4(aq) + Cu(s)$ : This reaction will take place because $Zn$ is more reactive than $Cu$ and can displace it from its salt solution.
$(ii)$ $Fe(s) + ZnSO_4(aq) \rightarrow FeSO_4(aq) + Zn(s)$ : This reaction will not take place because $Fe$ is less reactive than $Zn$ and cannot displace $Zn$ from its salt solution.

(N/A) $(i)$ Calcium starts floating because the bubbles of hydrogen gas formed stick to its surface.
$Ca(s) + 2H_2O(l) \longrightarrow Ca(OH)_2(aq) + H_2(g)$
$(ii)$ In dry air,sodium reacts with oxygen to form sodium oxide. In moist air,it reacts with water vapor to form sodium hydroxide.
$4Na(s) + O_2(g) \longrightarrow 2Na_2O(s)$ (In dry air)
$2Na(s) + 2H_2O(l) \longrightarrow 2NaOH(aq) + H_2(g) + \text{Heat}$ (In moist air)
$(iii)$ Iron displaces copper from copper sulphate solution due to higher reactivity.
$Fe(s) + CuSO_4(aq) \longrightarrow FeSO_4(aq) + Cu(s)$
$(iv)$ Potassium reacts violently with cold water,releasing hydrogen gas and heat.
$2K(s) + 2H_2O(l) \longrightarrow 2KOH(aq) + H_2(g) + \text{Heat}$
$(v)$ Carbon dioxide dissolves in water under high pressure to form carbonic acid.
$CO_2(g) + H_2O(l) \longrightarrow H_2CO_3(aq)$

(N/A) Silver: It reacts with sulfur compounds in the air to form a black layer of silver sulfide.
$(b)$ Copper: It reacts with moist carbon dioxide in the air to form a green layer of basic copper carbonate.
$(c)$ Platinum: It is a noble metal and is highly resistant to corrosion.
$(d)$ Nickel or Chromium: These are added to iron to make stainless steel.
$(e)$ Sodium: It is a soft,reactive metal that does not exhibit the typical metallic luster because it reacts rapidly with air and moisture.

(N/A) $(i)$ Gold and platinum are noble metals that are highly lustrous and resistant to corrosion,making them ideal for jewellery.
$(ii)$ Copper is less reactive than hydrogen in the reactivity series,so it cannot displace hydrogen from dilute acids.
$(iii)$ Stainless steel is an alloy of iron with chromium and nickel,which forms a protective oxide layer that prevents rusting.
$(iv)$ Metals are malleable (can be beaten into sheets) and ductile (can be drawn into wires),allowing them to be shaped as required.
$(v)$ $HNO_3$ is a strong oxidizing agent. When it reacts with metals,it oxidizes the produced hydrogen gas $(H_2)$ into water $(H_2O)$ instead of releasing it.

(N/A) $Mg$ has a higher affinity for oxygen than carbon does,meaning $MgO$ is more stable than $CO_2$ at the temperatures required for reduction.
$(b)$ Sodium is obtained by the electrolytic reduction of molten sodium chloride $(NaCl)$.
At cathode: $2Na^+ + 2e^- \rightarrow 2Na$
At anode: $2Cl^- \rightarrow Cl_2 + 2e^-$
$(c)$ Copper is obtained from its sulphide ore $(Cu_2S)$ by roasting followed by self-reduction:
$2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$
$2Cu_2O + Cu_2S \rightarrow 6Cu + SO_2$

(A-D) The coating on silver is silver sulphide $(Ag_2S)$ and on copper is basic copper carbonate $(CuCO_3 \cdot Cu(OH)_2)$.
$(b)$ Galvanisation is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc. The purpose is to prevent corrosion,as the zinc layer acts as a sacrificial anode and protects the underlying metal even if the coating is scratched.
$(c)$ An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal. It is prepared by melting the primary metal and then dissolving the other elements in it in a definite proportion,followed by cooling to room temperature.
$(i)$ When a small quantity of carbon is mixed with iron,it becomes hard and strong.
$(ii)$ When nickel and chromium are mixed with iron,it becomes stainless steel,which is hard and does not rust.

(N/A) Metals are chemically reactive in nature. They readily react with oxygen,sulfur,and other elements to form compounds such as oxides,sulfides,halides,carbonates,and sulfates. Due to this high reactivity,they are rarely found in their free (native) state in nature.
$(b)$ Metals are good conductors of heat because they possess free electrons. These free electrons move throughout the metallic lattice,effectively transferring kinetic energy from hotter regions to cooler regions,which facilitates the rapid conduction of heat.

(B) Element $A$ is a non-metal because non-metal oxides are typically acidic or neutral in nature.
$AO$ (e.g.,$CO$ - Carbon monoxide) is a neutral oxide.
$AO_2$ (e.g.,$CO_2$ - Carbon dioxide) is an acidic oxide.
Since metals generally form basic oxides,the formation of neutral and acidic oxides confirms that $A$ is a non-metal.

(A) We can store copper sulphate in a silver vessel because silver is less reactive than copper,so no displacement reaction occurs. However,we cannot store silver nitrate solution in a copper vessel because copper is more reactive than silver and will displace silver from its salt solution.
$Cu(s) + 2AgNO_{3}(aq) \rightarrow Cu(NO_{3})_{2}(aq) + 2Ag(s)$
$(b)$ Nitric acid $(HNO_{3})$ is a strong oxidizing agent. When zinc reacts with dilute $HNO_{3}$,the hydrogen gas produced is immediately oxidized to water $(H_{2}O)$,while the nitric acid itself gets reduced to nitrogen oxides like $N_{2}O$,$NO$,or $NO_{2}$.
$(c)$ Tin is less reactive than zinc. Zinc is more reactive and can easily react with organic acids present in food,potentially contaminating it. Tin provides a protective,non-reactive layer that preserves the food.

(N/A) $(i)$ Carbon acts as a reducing agent. In the reactivity series,zinc is less reactive than carbon,so carbon can displace oxygen from zinc oxide to form zinc metal:
$ZnO(s) + C(s) \rightarrow Zn(s) + CO(g)$
However,calcium is much more reactive than carbon and has a very high affinity for oxygen. Therefore,carbon cannot reduce calcium oxide to calcium.
$(ii)$ Copper and aluminium are used for electricity transmission because they possess high electrical conductivity and low electrical resistance,which minimizes energy loss during transmission.

(N/A) $(i)$ Alloys generally have higher electrical resistivity than their constituent pure metals. This property allows them to produce more heat when current passes through them. Additionally,they do not oxidize (burn) readily at high temperatures.
$(ii)$ Gold is a noble metal and is highly resistant to corrosion. It does not react with oxygen,moisture,or atmospheric gases,which is why it retains its luster for years.
$(iii)$ Iron reacts with oxygen and moisture present in the air to form hydrated iron$(III)$ oxide,commonly known as rust. Painting the grill creates a protective barrier that prevents the iron from coming into contact with air and moisture,thereby preventing rusting.

(B) Non-metals typically form acidic or neutral oxides.
$1$. Acidic oxides: These react with water to form acids. Among the given,$SO_2$ and $NO_2$ are acidic oxides.
$2$. Neutral oxides: These do not react with acids or bases to form salts. Among the given,$CO$,$H_2O$,and $N_2O$ are neutral oxides.

(N/A) $(i)$ Metals conduct electricity because they possess free electrons that are mobile. Consequently,they offer minimal resistance to the flow of electric current.
$(ii)$ The reaction between iron $(III)$ oxide $(Fe_{2}O_{3})$ and aluminium is highly exothermic. The heat released is sufficient to produce molten iron,which fills the cracks in machine parts. This is known as the thermite reaction:
$Fe_{2}O_{3}(s) + 2Al(s) \xrightarrow{\text{Heat}} 2Fe(l) + Al_{2}O_{3}(s)$
$(iii)$ These metals are stored under oil for two primary reasons:
$(a)$ They are highly reactive and can spontaneously catch fire upon contact with atmospheric oxygen.
$(b)$ They react readily with moisture and carbon dioxide in the air,forming a layer of oxides or carbonates on their surface.

(N/A) $(i)$ When a metal is heated,its atoms gain energy and vibrate more vigorously. This energy is transferred to the free electrons,which move through the metal lattice. These electrons transfer their kinetic energy to other atoms and electrons throughout the structure,making metals good conductors of heat.
$(ii)$ Pure gold,known as $24$ carat gold,is extremely soft and malleable. It is not suitable for making jewellery as it would easily deform. Therefore,a small amount of silver or copper is added to create an alloy,which makes the gold harder and more durable.
$(iii)$ Non-metals are electronegative and act as electron acceptors. To displace hydrogen from dilute acids,a substance must be able to donate electrons to $H^{+}$ ions to form $H_2$ gas. Since non-metals cannot provide electrons,they are unable to displace hydrogen from dilute sulphuric acid.

(D) An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal.
When an alloy is formed,the regular arrangement of atoms in the pure metal lattice is disrupted by the addition of other atoms.
This disruption hinders the movement of free electrons,which are responsible for electrical conduction,thereby decreasing the electrical conductivity compared to the pure metal.
Additionally,the presence of foreign atoms creates lattice distortions that require more energy to overcome during the phase transition from solid to liquid,which typically results in a lower melting point compared to the pure metal (though this can vary,the general property of alloys is lower conductivity and lower melting point than the base metal).

(C) An alloy is a homogeneous mixture of two or more metals,or a metal and a non-metal.
$24$ carat gold is pure gold,which is very soft and cannot be used for making jewellery.
To make it hard,it is alloyed with small amounts of silver or copper.
$22$ carat gold consists of $22$ parts of pure gold and $2$ parts of either copper or silver,making it an alloy.

(C) The process of depositing a layer of any desired metal on another material by means of electricity is known as $Electroplating$.
In this process,an electric current is passed through an electrolyte solution containing the metal to be deposited (in this case,gold) to coat the base metal (silver).
Therefore,the correct option is $C$.

(D) An oxide of a metal is formed when a metal reacts with oxygen.
$CaO$ (Calcium oxide) is a metal oxide.
$MgO$ (Magnesium oxide) is a metal oxide.
$Na_2O$ (Sodium oxide) is a metal oxide.
$CO_2$ (Carbon dioxide) is formed by carbon,which is a non-metal. Therefore,$CO_2$ is a non-metallic oxide (acidic oxide),not a metal oxide.

(B) Statement $B$ is incorrect because metals generally have high melting and boiling points due to strong metallic bonding.
Statement $A$ is correct as iron rusts in the presence of moisture and oxygen.
Statement $C$ is correct as calcination is the process of heating carbonate ores in limited supply of air.
Statement $D$ is correct as a more reactive metal displaces a less reactive metal from its salt solution.

(A) Stainless steel is an alloy primarily composed of iron $(Fe)$,chromium $(Cr)$,and nickel $(Ni)$.
Chromium is added to provide corrosion resistance,while nickel improves the mechanical properties and ductility of the steel.
Carbon is also present in small amounts,but the primary alloying elements that define stainless steel are iron,chromium,and nickel.

(B) An alloy is a homogeneous mixture of two or more metals,or a metal and a non-metal.
$A$. Copper $(Cu)$ is a pure chemical element.
$B$. Brass is an alloy consisting of copper $(Cu)$ and zinc $(Zn)$.
$C$. Chromium $(Cr)$ is a pure chemical element.
$D$. Magnesium $(Mg)$ is a pure chemical element.
Therefore,the correct answer is $B$.

(B) An alloy is a homogeneous mixture of two or more metals,or a metal and a non-metal.
$A$. Copper $(Cu)$ is a pure metal.
$B$. Magnalium is an alloy of aluminum $(Al)$ and magnesium $(Mg)$.
$C$. Iron $(Fe)$ is a pure metal.
$D$. Zinc $(Zn)$ is a pure metal.
Therefore,Magnalium is the correct answer.

(B) An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal.
Bronze is an alloy primarily composed of copper $(Cu)$ and tin $(Sn)$.
Brass is an alloy of copper $(Cu)$ and zinc $(Zn)$.
Steel is an alloy of iron $(Fe)$ and carbon $(C)$.
German silver is an alloy of copper $(Cu)$,zinc $(Zn)$,and nickel $(Ni)$.
Therefore,the correct option is $B$.