Textbook - Metals and Non-metals Questions in English

(N/A) $(i)$ Metal that exists in a liquid state at room temperature $\to$ Mercury $(Hg)$.
$(ii)$ Metal that can be easily cut with a knife $\to$ Sodium $(Na)$ or Potassium $(K)$.
$(iii)$ Metal that is the best conductor of heat $\to$ Silver $(Ag)$.
$(iv)$ Metals that are poor conductors of heat $\to$ Mercury $(Hg)$ and Lead $(Pb)$.

(N/A) Malleable: Substances that can be beaten into thin sheets are called malleable. For example,most metals are malleable.
Ductile: Substances that can be drawn into thin wires are called ductile. For example,most metals are ductile.

(A) Sodium $(Na)$ and potassium $(K)$ are highly reactive metals.
They react vigorously and explosively when exposed to air (oxygen) and water (moisture).
If kept in the open,they react with atmospheric oxygen and moisture,which can lead to accidental fires.
Therefore,to prevent these reactions and ensure safety,sodium is stored immersed in kerosene oil,as it does not react with kerosene.

(N/A) $(i)$ $3Fe_{(s)} + 4H_2O_{(g)} \rightarrow Fe_3O_{4(s)} + 4H_{2(g)}$
$(ii)$ Calcium with water: $Ca_{(s)} + 2H_2O_{(l)} \rightarrow Ca(OH)_{2(aq)} + H_{2(g)} + \text{Heat}$
$(iii)$ Potassium with water: $2K_{(s)} + 2H_2O_{(l)} \rightarrow 2KOH_{(aq)} + H_{2(g)} + \text{Heat}$

(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 $B > A > C > D$.

(N/A) Hydrogen gas $(H_2)$ is evolved when dilute hydrochloric acid $(HCl)$ is added to a reactive metal.
When iron $(Fe)$ reacts with dilute sulphuric acid $(H_2SO_4)$,iron$(II)$ sulphate $(FeSO_4)$ is formed along with the evolution of hydrogen gas $(H_2)$.
The chemical equation is:
$Fe(s) + H_2SO_4(aq) \longrightarrow FeSO_4(aq) + H_2(g)$

(N/A) Zinc is more reactive than iron. Therefore,when zinc is added to a solution of iron $(II)$ sulphate,it displaces iron from the solution,resulting in the formation of zinc sulphate and iron metal.
The chemical reaction is:
$Zn_{(s)} + FeSO_{4(aq)} \to ZnSO_{4(aq)} + Fe_{(s)}$

(N/A) $(i)$ The representation of elements with valence electrons as dots around the element symbol is referred to as the electron-dot structure.
$(a)$ Sodium $(2, 8, 1) = Na^{\bullet}$
$(b)$ Oxygen $(2, 6) = :\ddot{O}:$
$(c)$ Magnesium $(2, 8, 2) = Mg^{\bullet\bullet}$
$(ii)$ Formation of $Na_{2}O$:
$2Na^{\bullet} + :\ddot{O}: \rightarrow (Na^{+})_{2}[:\ddot{O}:]^{2-}$
Formation of $MgO$:
$Mg^{\bullet\bullet} + :\ddot{O}: \rightarrow (Mg^{2+})[:\ddot{O}:]^{2-}$
$(iii)$ The ions present in $Na_{2}O$ are $Na^{+}$ and $O^{2-}$ ions,and in $MgO$ are $Mg^{2+}$ and $O^{2-}$ ions.

(N/A) Ionic compounds are formed by the transfer of electrons between atoms,resulting in the formation of positively charged cations and negatively charged anions.
These oppositely charged ions are held together by strong electrostatic forces of attraction.
To melt an ionic compound,a significant amount of energy is required to overcome these strong inter-ionic forces.
Consequently,ionic compounds exhibit high melting points.

(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.

(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 $CuO$ $(Mg + CuO \rightarrow MgO + Cu)$

(B) The reactivity of a metal is directly proportional to its tendency to corrode.
Metals that are less reactive,such as gold,silver,and platinum,do not react easily with atmospheric oxygen,moisture,or other chemicals.
Therefore,these metals are highly resistant to corrosion and do not corrode easily.

(N/A) Alloys are homogeneous mixtures of two or more elements.
The elements can be two metals,or a metal and a non-metal.
An alloy is formed by first melting the primary metal and then dissolving the other elements in it.
For example,$Steel$ is an alloy of $Iron$ and $Carbon$.

(D) displacement reaction occurs when a more reactive metal displaces a less reactive metal from its salt solution.
According to the reactivity series,copper $(Cu)$ is more reactive than silver $(Ag)$.
Therefore,copper can displace silver from silver nitrate $(AgNO_{3})$ solution.
The chemical reaction is: $Cu(s) + 2AgNO_{3}(aq) \rightarrow Cu(NO_{3})_{2}(aq) + 2Ag(s)$.
In the other options,the metal added is less reactive than the metal present in the salt solution,so no displacement reaction will occur.

(A) The correct method is applying a coating of zinc (galvanization).
While applying grease or paint can prevent iron from rusting in general,these methods are not suitable for an iron frying pan.
When the pan is heated during cooking or washed repeatedly,the layers of grease or paint would be destroyed or contaminate the food.
Galvanization (coating with zinc) provides a more durable protective layer that is better suited for metallic cookware.

(B) The element is likely to be calcium $(Ca)$.
Calcium reacts with oxygen to form calcium oxide $(CaO)$,which is an ionic compound.
Ionic compounds typically have high melting points due to strong electrostatic forces of attraction between ions.
Calcium oxide $(CaO)$ reacts with water to form calcium hydroxide $(Ca(OH)_2)$,which is soluble in water.

(C) Food cans are coated with tin instead of zinc because zinc is more reactive than tin.
When food (which often contains organic acids) comes into contact with a zinc coating,the zinc reacts with the acids to form toxic zinc salts,which can contaminate the food.
In contrast,tin is less reactive than zinc and does not react easily with food acids,making it a safer choice for preserving food.

(N/A) With the hammer,we can beat the sample. If it can be beaten into thin sheets (i.e.,it is malleable),then it is a metal; otherwise,it is a non-metal.
Similarly,we can use the battery,bulb,wires,and a switch to set up an electrical circuit with the sample. If the sample conducts electricity,the bulb will glow,indicating it is a metal; otherwise,it is a non-metal.
$(b)$ These tests are useful in distinguishing between metals and non-metals because they are based on fundamental physical properties such as malleability and electrical conductivity. These tests are simple,quick,and do not involve any complex chemical reactions.

(N/A) Amphoteric oxides are those metal oxides which react with both acids as well as bases to produce salts and water.
These oxides exhibit dual nature,showing both acidic and basic properties.
Examples: Aluminium oxide $(Al_2O_3)$ and Zinc oxide $(ZnO)$.

(N/A) Metals that are more reactive than hydrogen in the reactivity series can displace it from dilute acids. Examples of such metals are $Sodium$ $(Na)$ and $Magnesium$ $(Mg)$.
Metals that are less reactive than hydrogen cannot displace it from dilute acids. Examples of such metals are $Copper$ $(Cu)$ and $Silver$ $(Ag)$.

(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.

(N/A) $(i)$ There will be no action on dry litmus paper.
$(ii)$ Since the gas is sulphur dioxide $(SO_2)$,it turns moist blue litmus paper to red because sulphur dioxide reacts with moisture to form sulphurous acid.
$(b)$ $S_{(s)} + O_{2(g)} \to SO_{2(g)}$
$SO_{2(g)} + H_2O_{(l)} \to H_2SO_{3(aq)}$

(N/A) Two ways to prevent the rusting of iron are:
$(i)$ Oiling,greasing,or painting: By applying oil,grease,or paint,the surface becomes waterproof,and the moisture and oxygen present in the air cannot come into direct contact with the iron. Hence,rusting is prevented.
$(ii)$ Galvanisation: An iron article is coated with a layer of zinc metal,which prevents the iron from coming into contact with oxygen and moisture. Hence,rusting is prevented.

(B) Non-metals react with oxygen to form acidic oxides.
For example:
${S_{(s)}} + {O_{2(g)}} \to {SO_{2(g)}}$ (which is acidic in nature).
When these oxides are dissolved in water,they form acids. For instance,${SO_2} + H_2O \to H_2SO_3$ (sulfurous acid).

(N/A) Platinum,gold,and silver are used to make jewellery due to the following reasons:
$1$. Lustre: These metals possess a high degree of metallic lustre,which makes them attractive and suitable for ornaments.
$2$. Low Reactivity: They are noble metals and are very less reactive. They do not react with air,water,or acids under normal conditions,which prevents them from corroding or tarnishing easily.
$3$. Malleability and Ductility: These metals are highly malleable and ductile,allowing them to be easily shaped into intricate designs.

(N/A) Copper reacts with moist carbon dioxide in the air to form copper carbonate,which results in the copper vessel losing its shiny brown surface and forming a green layer of copper carbonate.
The citric acid present in lemon or tamarind juice neutralizes the basic copper carbonate and dissolves the layer.
This is why tarnished copper vessels are cleaned with lemon or tamarind juice to restore the characteristic lustre of the copper surface.

(A)

Metal	Non-metal
Metals are electropositive.	Non-metals are electronegative.
They react with oxygen to form basic oxides. $4Na + O_2 \longrightarrow 2Na_2O$. These typically form ionic bonds.	They react with oxygen to form acidic or neutral oxides. $C + O_2 \longrightarrow CO_2$. These typically form covalent bonds.
They react with water to form oxides or hydroxides and hydrogen gas. $2Na + 2H_2O \longrightarrow 2NaOH + H_2 \uparrow$.	They generally do not react with water.
They react with dilute acids to form salt and hydrogen gas. $2Na + 2HCl \longrightarrow 2NaCl + H_2 \uparrow$.	They do not react with dilute acids as they cannot displace hydrogen.
They act as reducing agents because they easily lose electrons. $Na \longrightarrow Na^+ + e^-$.	They act as oxidizing agents because they gain electrons. $Cl_2 + 2e^- \longrightarrow 2Cl^-$.

(A) The man must have used $Aqua$ $Regia$ to clean the ornaments.
$Aqua$ $Regia$ is a freshly prepared mixture of concentrated $HCl$ and concentrated $HNO_3$ in a $3:1$ ratio.
It is a highly corrosive and fuming liquid capable of dissolving noble metals like gold.
When the gold bangles were dipped in this solution,the outer layer of the gold was dissolved,exposing the fresh,shiny inner layer,which made the bangles look new.
However,because the outer layer of gold was dissolved into the solution,the total weight of the bangles was significantly reduced.

(N/A) Copper does not react with cold water,hot water,or steam.
However,iron reacts with steam.
If the hot water tanks are made of steel (an alloy of iron),the iron present in the steel would react vigorously with the steam formed from the hot water.
$3Fe(s) + 4H_2O(g) \to Fe_3O_4(s) + 4H_2(g)$
This reaction would lead to the corrosion and degradation of the tank.
That is why copper is used to make hot water tanks,and not steel.

(N/A) $Sodium$,$potassium$,and $lithium$ are highly reactive metals that react vigorously with both air and water. To prevent them from coming into contact with atmospheric oxygen and moisture,which could lead to spontaneous combustion or oxidation,they are stored immersed in kerosene oil.

(N/A) Although aluminium is a highly reactive metal,it is resistant to corrosion.
This is because aluminium reacts with oxygen present in the air to form a thin,protective layer of aluminium oxide $(Al_2O_3)$.
This oxide layer is very stable and non-porous,which prevents further oxidation and corrosion of the underlying metal.
Additionally,aluminium is lightweight,durable,and an excellent conductor of heat,making it an ideal material for manufacturing cooking utensils.

(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.