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1. Metals are solid at room temperature. But mercury is such a metal which is liquid at room temperature.
2. All metals have a shining surface. They are lustrous. This property is called metallic lustre.
3. Metals are generally hard but alkaline metals (lithium, sodium, potassium) are so soft that they can be cut with a knife.
4. Metals are good conductors of electricity and heat. Silver and copper are the best conductors of heat. In comparison, lead and mercury are poor conductors of heat.
5. The melting point of metals is very high. But the melting point of gallium and cesium is very low. If these metals are kept on the palm, they melt immediately.
6. The metals are ductile. The ability of metals to be drawn into thin wires is called ductility.Gold is the most ductile metal.
7. When metals strike a hard surface, they produce sound. The metals which produce sound when struck against a hard surface are called sonorous.
8. Metals can be beaten into thin sheets. This property is called malleability. Gold and Silver are the most malleable metals.
Example - Iron, copper, silver, gold, mercury, aluminium, zinc etc.
❖Physical properties of nonmetals
1. All non-metals are either solids or gases, but bromine is such a non-metal which is a liquid
2. Non-metals are generally brittle.
3. Non-metals are no lustrus, but iodine is a non-metal which is lustrous.
4. Non-metals are bad conductors of electricity and heat. But graphite is a good conductor of electricity and heat.
Example- Carbon, Sulphur, Iodine, Oxygen, Hydrogen etc.
Allotropy - Two or more forms of the an elements, which differ in their physical properties but have same chemical properties are called allotropes and this type of behavior is called allotropy. Diamond, an allotrope of carbon, is the hardest natural substance known and has a very high melting and boiling point. Graphite, another allotrope of carbon, is a conductor of electricity.
❖Chemical properties of metals
1. Reaction of metals with air (Oxygen)
Almost all metals react with oxygen to form metal oxides. Metal oxides are basic in nature.
Metal + Oxygen ⟶ Metal oxide
Example:-
When copper is heated in the presence of air, it combines with oxygen to form black colored copper oxide.
Cu + O₂ ⟶ 2CuO
When aluminum is heated in the presence of air, it combines with oxygen to form aluminum oxide.
4Al + 3O₂ ⟶ 2Al₂O₃
Most of the metal oxides are insoluble in water but sodium oxide and potassium oxide dissolve in water to form alkalis.
Na₂O + H₂O ⟶ 2NaOH
K₂O + H₂O ⟶ 2KOH
Some metals like potassium and sodium react with oxygen so vigorously that they catch fire when kept in the open. Therefore, they are kept immersed in kerosene oil for safe keeping and to prevent accidental fire.
At ordinary temperature, the surfaces of metals such as magnesium, aluminium, zinc, lead, etc., are covered with a thin layer of oxide. This layer of oxide protects the metals from further oxidation.
Iron does not burn on heating but iron filings burn vigorously when sprinkled in the flame of the burner.
Copper does not burn, but a black layer of copper(II) oxide is formed on the hot metal.
Silver and gold do not react with oxygen even at high temperatures.
❖ Anodization
The process of forming a thick oxide layer on aluminum is called anodization. Aluminium develops a thin oxide layer when exposed to air.
This layer of aluminum oxide protects it from corrosion. By making this layer thicker, it can be more protected from corrosion.
❖ Amphoteric oxide
Such metal oxides which react with both acids and bases to produce salt and water are called amphoteric oxides. Amphoteric oxides show both acidic and basic behaviour. Like aluminum oxide (Al₂O₃) and zinc oxide (ZnO).
Aluminium oxide reacts with acids and bases –
Al₂O₃ + 6HCl ⟶ 2AlCl₃ + 3H₂O
Al₂O₃ + 2NaOH ⟶ 2NaAlO₂ + H₂O
(Sodium aluminate)
ZnO + 2HCl ⟶ ZnCl₂ + H₂O
ZnO + 2NaOH ⟶ Na₂ZnO₂ + H₂O
(Sodium zincate)
Such metal oxides which react with both acids and bases to produce salt and water are called amphoteric oxides. Amphoteric oxides show both acidic and basic behaviour. Like aluminum oxide (Al₂O₃) and zinc oxide (ZnO).
Aluminium oxide reacts with acids and bases –
Al₂O₃ + 6HCl ⟶ 2AlCl₃ + 3H₂O
Al₂O₃ + 2NaOH ⟶ 2NaAlO₂ + H₂O
(Sodium aluminate)
ZnO + 2HCl ⟶ ZnCl₂ + H₂O
ZnO + 2NaOH ⟶ Na₂ZnO₂ + H₂O
(Sodium zincate)
2. Reaction of metals with water :
Metals react with water to produce hydrogen gas and metal oxides. These metal oxides dissolve in water and make metal hydroxides
Metal + Water ⟶Metal Oxide + Hydrogen
Metal oxide + Water ⟶Metal hydroxide
Different metals shows different reaction with water.
1. Na and K react with cold water and reaction is so violent and exothermic that the evolved/realised hydrogen immediately catches fire.
2K + 2H₂O → 2KOH + H₂ + heat energy
2Na + 2H₂O → 2NaOH + H₂ + heat energy
2. The reaction of calcium with water is slow. Here the heat released is not sufficient for the hydrogen to catch fire. The bubbles of hydrogen gas formed in this reaction stick to the surface of the calcium metal. So calcium starts floating on water.
Ca(s) + 2H₂O(l) ⟶ Ca(OH)₂(aq) + H₂ (g)
3, Magnesium does not react with cold water but reacts with hot water to form magnesium hydroxide and hydrogen gas.The bubbles of hydrogen gas formed in this reaction stick to the surface of the Magnesium metal. So Magnesium also starts floating on water.
2Mg + 2H₂O → 2Mg(OH)₂ + H₂
4. Aluminium, iron and zinc do not react either with cold or hot water. But they react with steam to form the metal oxide and hydrogen gas.
2Al + 3H₂O(g) → Al₂O₃ + 3H₂
3Fe + 4H₂O(g) → Fe₃O₃ + 4H₂
5. Metals like lead, copper, silver and gold do not react with water at all.
3. Reaction of metal with acid :
Metals react with acids to give the corresponding salt and hydrogen gas.
Acid + Metal → Salt. + Hydrogen gas
Example-
Magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen gas.
Mg + HCl → MgCl₂ + H₂
Hydrogen gas is not evolved when a metals react with nitric acid. Because HNO₃ is a strong oxidizing agent which oxidises the generated H₂ to water and itself is reduced to an oxide of nitrogen.
Magnesium and Manganese react with very dilute HNO₃ to evolve H₂ gas.
Aqua regia (Royal water/Amalraj) :- A fresh mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3:1 is called aqua regia. Aqua regia is a highly corrosive fumming liquid. It is one of reagents that is able to dissolve gold and platinum.
4. Reaction of metal with other metal salts :
The more reactive metal displaces the less reactive metal from its compound in solution.
Example-
When an iron nail is dipped in copper sulphate solution, iron displaces copper from copper sulphate and ferrous sulphate is formed.
Fe + CuSO₄ → FeSO₄ + Cu
In the above reaction, more reactive Fe displaces less reactive Cu from its compound.
❖ Activity Category
Activity series is a list in which metals are arranged in decreasing order of their reactivity.
K → potassium
Na → sodium
Ca → calcium Most reactive
Mg → Magnesium
Al → Aluminum
Zn → Zinc
Fe → Iron
Pb → lead Medium reactive
H → Hydrogen
Cu → Copper
Hg → Mercury
Ag → Silver is the Least reactive
5. Reaction of metals and non-metals
Reactivity of elements is a tendency to attain a completely filled valence shell. atoms of the metal lose electron to form cation and atoms of non-metal gain electrons to form anion.
Example-
Formation of sodium Chloride:
Sodium atom loses one electron in its outermost shell to form sodium cation [Na+].
Na → Na⁺ + e-
2,8,1 2,8
On the other hand, chlorine has 7 electrons in its outermost shell. Chlorine accepts one electron lost by sodium to complete its octet. and forms chloride anion [Cl-]
Cl + e- → Cl⁻
2,8,7 2,8,8
Sodium and chloride ions, being oppositely charged, attract each other and bind in strong electrostatic force to form sodium chloride.
Formation of Magnesium chloride
Mg → Mg²⁺ + 2e⁻
2,8,2 2,8
Cl + 2e⁻ → Cl⁻
2,8,7 2,8,8
2,8,2 2,8
Cl + 2e⁻ → Cl⁻
2,8,7 2,8,8
Formation of Kalcium chloride
K → K⁺ + e⁻
2,8,8,1 2,8,8
Cl + 2e⁻ → Cl⁻
2,8,7 2,8,8
2,8,8,1 2,8,8
Cl + 2e⁻ → Cl⁻
2,8,7 2,8,8
Ionic Compounds : The compounds formed by the transfer of electrons from a metal to a non-metal are called ionic compounds or electrovalent compounds.
properties of ionic compounds
1. Physical nature : Ionic compounds are solids and are somewhat hard because of the strong force of attraction between the positive and negative ions. These compounds are generally brittle and break into pieces when pressure is applied.
2. Melting point and boiling point: Ionic compounds have very high melting and boiling points because a considerable amount of energy is required to break the strong inter-ionic attraction.
3. Solubility: Ionic compounds are generally soluble in water and insoluble in solvents like kerosene, petrol etc.
4. Conduction of electricity: Ionic compounds do not conduct electricity in solid state because movement of ions is not possible in solid state due to rigid structure. But ionic compounds conduct electricity in molten state because ions are present in aqueous solution of ionic compounds. When an electric current is passed through the solution, these ions start moving towards the opposite electrode. and conduct electricity.
Metallurgy. - All the processes involved in the extraction of metals from ore, is called metallurgy.
The extraction of metals from their ores and then refining them for use is known as metallurgy.
Extraction of Metals
Mineral: The elements or compounds, which occur naturally in the earth’s crust, are known as minerals. e.g., Mica.
Ores - These minerals which contain a very high percentage of a particular metal and the metal can be profitably extracted from it are called ores.
Enrichment of Ores
Many impurities like soil, sand etc. are found in the ores mined from the earth, These impurities are called gangs and removal of impurities is called enrichment of ores.
Metallurgy.-All the processes involved in the extraction of metals from ore, is called metallurgy.
1. Extracting Metals Low in the Activity Series :
The metals at the bottom of the activity series are the least reactive. They are often found in a free state. For example, gold, silver, platinum and copper are found in the free state. Copper and silver are found in the combined state as their sulphide or oxide ores. The metal can be obtained only by heating the oxides of these metals.
Extraction of mercury from mercury ore cinnabar
The ore of mercury is cinnabar (HgS). When cinnabar (HgS) is heated in air, it gets converted into mercuric oxide.
2HgS + 3O₂ → Heating → 2HgO + 2SO₂
Mercuric sulphide mercuric oxide
Self-Reduction: On heating mercuric oxide further, it gets reduced to mercury.
2HgO → Heating → 2Hg + O₂
Mercuric oxide
Similarly, copper which is found as Cu₂S in nature can be obtained from its ore by just heating in air.
Roasting:
Cu₂S(s) + 3O₂ (g) → Heating → 2Cu₂O(s) + SO₂ (g)
Self-Reduction:
2Cu₂O(s) + Cu₂S(s) → Heating → 6Cu(s) + SO₂(g)
2. Extracting Metals in the Middle of the Activity Series :
The metals in the middle of the activity series (Zn, Fe, Pb, etc.) are moderately reactive. They are found in the earth’s crust mainly as oxides, sulphides or carbonates. It is easier to obtain the metal from its oxide ore than from a sulphide or carbonate ore. Therefore, first the sulphide and carbonate ores of the metal are converted into metal oxide.
Roasting :- Heating of sulphide ore at high temperature in the presence of excess air, it is converted into oxide. This process is called Roasting.
Calcination :- Heating of Carbonate ore at high temperature in the presence limited amount of air or in absent of air, it is converted into oxide. This process is called Calcination.
The metal oxide obtained in this way is reduced in the presence of a reducing agent such as carbon to obtain a metal.
Example:- Extraction of Zinc
Roasting
2ZnS + 3O₂ → Heating → 2ZnO+ 2SO₂
Calcination
ZnCO₃ → Heating → ZnO+ CO₂
when zinc oxide is heated with carbon, it is reduced to metallic zinc.[Reduction]
ZnO + C → Heating → Zn + CO
Sometimes the highly reactive metals such as sodium, calcium, aluminium, etc., are used as reducing agents. For example, when manganese dioxide is heated with
aluminium powder, the following reaction takes place –
3MnO₂ + 4Al → 3Mn + 2Al₂O₃ + Heat [Displacement]
✠Thermit Reaction : When iron oxide (Fe₂O₃) reacts with Aluminum, a large amount of heat is released. The amount of heat released is so large that the iron metal is obtained in molten state. This reaction is known as the thermit reaction
Fe₂O₃ + Al → Fe + Al₂O₃ + Heat
This reaction is used to join the railway tracks or cracked machine parts.
3. Extracting Metals towards the Top of the Activity Series
The metals at the top of the reactivity series such as Sodium, Magnesium, Calcium, Aluminum etc. are extremely reactive. Therefore it cannot exist in the free state. These metals are obtained by electrolytic reduction.
Extraction of sodium metal from sodium chloride
Sodium, Magnesium and Calcium are obtained by the electrolysis of their molten chlorides.The metals are deposited at the cathode , whereas, chlorine is liberated at the anode
Electrolysis of sodium chloride
Na⁺ + e– → Na at cathode
2Cl⁻ → Cl₂ + 2e– at anode
Refining of Metals
The metals produced by reduction processes are not very pure. They contain impurities. The removal of these impurities from metals to obtain pure metals is called refining. Impurities are removed from metals by electrolytic refining method.
Electrolytic refining
Many metals, such as copper, zinc, tin, nickel, silver, gold, etc., are refined electrolytically. In this process, impure metal is made anode and a thin layer of pure metal is made cathode. Metal salt solutions are used as electrolytes. When current is passed through the electrolyte, the impure metal at the anode dissolves in the electrolyte. And an equal amount of pure metal is deposited on the cathode . The soluble impurities dissolve in the solution and the insoluble impurities settle down at the bottom of the anode and are known as anode mud.
At cathode Na⁺ + e⁻ → Na
At anode 2Cl⁻ → Cl₂ + 2e⁻
Corrosion : When a metal is attacked by substances around it such as moisture, acids, etc., it is said to corrode and this process is called corrosion.
❖ Silver articles become black after some time when exposed to air. This is because it reacts with sulphur [H₂S] in the air to form a layer of silver sulphide.
❖ When copper is exposed to air, its surface slowly loses its brown luster.This is because copper reacts with moist carbon dioxide present in the air to form a layer of green colored copper carbonate on its surface.
❖ If iron is kept in moist air for a long time, iron reacts with oxygen and water present in the air to form brown colored layer of ferric oxide on itself, which is called rust.
corrosion protection
1. By painting, oiling, greasing,
2. By galvanising
3. By chrome plating
4. Anodization
5. Alloying
Galvanisation- The method of coating iron and steel with a thin layer of zinc to protect them from corrosion is called Galvanisation. Even after the zinc layer is destroyed, the zinc coated article remains safe from rust.
Metal Alloys
A homogeneous mixture of two or more metals /non-metals is called an alloy. The properties of the alloy are better than the properties of the primary metal.
The alloys are hard and strong than the pure metal.
The electrical conductivity of alloys are less than the pure metal.
The melting point of alloys are less than the pure metal.
The alloys are more resistance towards corrosion than the pure metal.
The electrical conductivity and melting point of alloy are less than the pure metal.
Brass, an alloy of copper and zinc (Cu and Zn), and bronze, an alloy of copper and tin (Cu and Sn), are not good conductors of electricity
Solder, an alloy of lead and tin (Pb and Sn), has a low melting point and is used for welding electrical wires together.
Example
1. Iron cannot be used in its pure state. This is because pure iron is very soft and easily stretched when heated. If it is mixed with a small amount of carbon (about 0.05 %), it becomes hard and strong
2. Pure gold, known as 24 carat gold and it is very soft. therefore it is not suitable for making jewellery. It is alloyed with either silver or copper to make it hard. In India, 22 carat gold is mostly used for making jewellery. It means that 22 parts of pure gold is alloyed with 2 parts of either copper or silver.
3. Stainless steel - Stainless steel is an alloy of iron, nickel and chromium which is hard and does not rust.
4. Amalgam - An alloy made of mercury and any other metal is called amalgam.
5. Bronze – Copper + Tin.
6. Brass - Copper + Zinc.
7. Solder - Lead + Tin.
- Name the “A lustrous coloured non-metal.” ?
Iodine - Give one most suitable word for” Iodine, a shining non-metal.”?
Lustrous. - Name a non-metal which is lustrous whereas a metal which is non-lustrous.
Iodine is a lustrous non-metal, Lead is a non-lustrous metal. - Write one example of a metal which is so soft, that it can be cut with a knife.?
Sodium is so soft that it can be easily cut with a knife. - Name the metal which is a poor conductor of heat.?
Lead/Mercury - Write one example of the best conductor of heat and poorest conductor of heat.
Silver is the best conductor and lead/merucary is a poor conductor of heat. - Name the metal which melts when kept on palm.?
Gallium - Which of the following two metals will melt at body temperature (37°C): Gallium, Magnesium, Ceisium, Aluminium?
Gallium and Caesium will melt at the body temperature. - Name the metals Which have low melting point.?
Gallium and Caesium. - Name the metal which does not stick to the glass,
Mercury. - Write one example of ‘A metal with highest melting point and a metal with lowest melting point. ?
Tungsten has highest melting point, mercury has lowest melting point. - Write one example of most malleable and most ductile metal.?
Gold is most malleable and ductile. - Which is used to galvanise iron articles?
Zinc metal is used for coating over iron metal to galvanise iron. - Give reason for the "school bells are made up of metals."?
Metals are sonorous i.e., produce sound when struck with a hard substance. - Why are electric wires are coated with PVC or a rubber-like material?
PVC is an insulator which protects us from electric current /electric shock. - Metals can be given different shapes according to our needs.
Metals are malleable, therefore they can be given different shapes - Give one most suitable word for "some metals produce a sound on striking with a hard surface."
Sonorous - Name two metals which are used to make jewellery
Gold and platinum - Name the metal which is preserved in kerosene.
Sodium or Potassium - A metal (E) is stored under kerosene oil. When a small piece of it is left open in air, it catches fire. When the product formed is dissolved in water, it turns red litmus blue. Name the metal (E).
E is sodium metal. - Write the chemical equation for the reaction taking place when Copper is heated in air.
2Cu(s) + O₂ (g) ⟶ 2CuO(s) - Write chemical equations for the reaction taking place when iron is strongly heated with air.
3Fe(s) + 2O₂ (g) Heat Fe₃O₄ (s) - Choose the amphoteric oxide amongst the following: Na₂O, ZnO, Al₂O₃, CO₂, H₂O
ZnO and Al₂O₃ are amphoteric oxides. - A green layer is gradually formed on copper plate when left exposed to air for a week in a bathroom. What could this green substance be?
CuCO₃ .Cu(OH)₂ , Basic copper carbonate. - What is the nature of Zinc oxide?
It is amphoteric oxide. - Give one most suitable word for "Metal oxides which show basic as well as acidic behaviour."?
Amphoteric oxides - Name a metal it does react with any physical state of water.
Au - Name any one metal which reacts neither with cold water nor with hot water but reacts with heated steam to produce hydrogen gas.
Aluminium(Al)/ Iron (Fe) - Write the chemical equation for the reaction taking place when steam is passed over hot Aluminium?
2Al(s) + 3H₂O(g) → Al₂O₃ (S) + 3H₂ (g) - Write the chemical equation for the reaction taking place when Iron reacts with steam.
3Fe(s) + 4H₂ O(g) Heat Fe₃ O₄ (s) + 4H₂ (g) - Write the chemical equation for the reaction taking place when Magnesium (Mg) reacts with dilute HCl.
Mg(s) + 2HCl(dil.) ⟶ MgCl₂ (aq) + H₂ (g) - Write the balanced chemical equation of Mg metal is reacted with very, little amount of dilute HNO₃.
Mg + dilHNO₃ ⟶ MgNO₃ + NO + H₂O - Arrange the following metals in decreasing order of reactivity are Na, K, Cu, Ag
K > Na > Cu > Ag is the decreasing order of reactivity. - X + YSO₄ ⟶ XSO₄ + Y and Y + XSO₄ ⟶ No reaction.
Out of the two elements, X and Y, which is more reactive and why?
X is more reactive than Y because it is displacing Y from its salt solution. - Arrange the metals: gold, copper, iron and magnesium in the order of their increasing reactivity.
Au < Cu < Fe < Mg is the increasing order of reactivity. - Whose articles when exposed to air forms a black coating?
Silver articles become black after some time when exposed to air. - What is corrosion of iron called?
Corrosion of iron is called rusting - What is the formula of rust?
Rust is hydrated ferric oxide, Fe₂O₃.xH₂O - Why do we apply paint on iron grills ?
Iron grills are painted to prevent them from rusting. - Why corrosion of iron metal is a serious problem?
It weakens bridges and materials and a lot of iron gets wasted every year. - Which is alloyed with other metal to make amalgam?
Mercury is alloyed with other metals to form amalgam. - What is amalgam ?
An alloy made of mercury and any other metal is called amalgam. - Name a non-metal which makes iron hard and strong?
Carbon makes iron hard and strong. - Write the constituents of Bronze.
Bronze, is an alloy of copper and tin (Cu and Sn) - Write the constituents of Brass.
Brass, is an alloy of copper and zinc (Cu and Zn) - Which property makes solder alloy suitable for welding electric wires?
Its melting point is low which makes solder suitable for welding electric wires. - An alloy has low melting point and is therefore used for electrical fuse. Name the alloy and write its constituents.
Solder is an alloy. It is made up lead and tin. - Name two metals which are found in nature in free state.
Gold and silver are found in free state. - Name any two metals used as reducing agents by displacing metals of low reactivity from their compounds.
Al and Mg. - Name two metals which react with dilute HNO₃ to evolve H₂ gas.
Or
Name two metals which displaces hydrogen on reaction with dill. nitric acid.
Mg and Mn - In electrolytic refining of impure copper metal, what are used as cathode and anode?
Pure copper is used as the cathode and impure copper is used as the anode. - Write one example of a non-metal which is the hardest known substance.
Diamond (an allotrope of Carbon) is a non-metal which is the hardest known substance - Why are ionic compounds usually hard?Ionic compounds are hard due to strong force of attraction between the positive and negative ions.
- Define metallurgy.
All the processes involved in the extraction of metals from ore, is called metallurgy. - Name one metal and one non-metal in liquid state at room temperature. ?
Mercury is a metal and Bromine is a non-metal present as a liquid at room temperature. - Define corrosion.
The process in which a metal react with substances present in atmosphere such as moisture, acids, etc., to form surface compounds is called corrosion. - Explain the following statement: "Some alkali metals can be cut with knife."?
Alkaline metals (lithium, sodium, potassium) are so soft that they can be cut with a knife. - Why do we use copper and aluminium wire for transmission of electric current?
Copper and aluminium are ductile and good conductors of electricity, therefore they are used in transmission wires. - Give reason why: Electric wires are coated with plastic. ?
Plastic is a non-conductor of electricity, therefore electric wires are coated with plastic. - Why do gold ornaments remain their lustre even after several years of use.
Gold is least reactive and do not react with substances present in the atmosphere, therefore remain lustrous for a long time - Why do we use gold,Platinum and Silver metals in jewellery?
Gold and Silver are lustrous metals and do not react with substances present in the atmosphere, therefore remain lustrous for a long time - What happens when carbon dioxide is compressed in water at high pressure?
CO₂ + H₂O ⟶ H₂CO₃ Carbonic acid is formed.
Most non-metals produce acidic oxides when dissolve in water. - At ordinary temperature the surface of metals such as magnesium, aluminium, zinc etc. is covered with a thin layer. What is the composition of this layer? State its importance.
The composition of this layer is metal oxide. This layer of oxide protects the metals from further oxidation - Most metal oxides are insoluble in water but some of these dissolve in water. What are these oxides and their solution in water called?
Sodium oxide and potassium oxide dissolve in water. These oxides are called basic oxides and their solution are called alkalies. - Give reasons for the following: Aluminium oxide is considered has amphoteric oxide.
Aluminium oxide reacts with both acids and bases to produce salt and water therefore it is considered has amphoteric oxide. - Hydrogen is not a metal but has been assigned a place in the reactivity services of metals. Why?
Like metal, hydrogen also has a tendency to lose electron and forms a positive ion H⁺ therefore it is included in the activity series. - In nature, aluminium is found in combined state whereas silver/gold are found in free state. Give reason.
Aluminium is reactive metal, therefore it is found in combined state whereas silver/gold are less reactive metals and so are found in free state. - Why do silver ornaments lose their shine when kept in open air for sometime?
Silver reacts with H₂S present in the atmosphere to form a layer of silver sulphide. due to which it loses its shine. - How will you recognise the phenomena of corrosion of silver?
Silver reacts with H₂S present in the atmosphere to form a black colour compound Silver Sulphide. This phenomenon is called corrosionf of silver. - Why do silver articles turn black and copper items turn green after sometime?
Silver turns black due to the formation of Ag₂ S, (Silver sulphide).
Copper turns green due to formation of basic copper carbonate. - How can we prevent corrosion of iron?
We can prevent corrosion of iron by 1. Painting, 2. Oiling and greasing, 3. Galvanisation, 4. By forming its alloys. - Why is iron galvanised with zinc? Can it be galvanised with copper? If not, why?
Iron is galvanised by zinc because zinc is more reactive than Fe. Iron cannot be galvanised by copper because copper is less reactive than iron - Define Galvanisation
The method of coating iron and steel with a thin layer of zinc to protect them from corrosion is called Galvanisation. - The galvanised iron article is protected against rusting even if the zinc layer is broken. Why?
zinc is more reactive than iron, therefore it can be easily oxidized. Thus when zinc layer breaks down, the zinc gets oxidised before iron and prevents its corrosion. - Why does stainless steel not get rusted easily?
Stainless steel is an alloy of iron, nickel and chromium therefore it does not get rusted. - Iron is not used in pure state. Give reason.
Iron cannot be used in its pure state. This is because pure iron is very soft and easily stretched when heated. - Why are alloys used for making bells and strings of music instruments.
Alloys are stronger and more sonorous than metals and used for bells and musical instruments. - The reaction of metal X with Fe₂O₃ is highly exothermic and is used to join railway tracks. Identify metal X. Write the chemical equation for the reaction.
(i) X is Aluminium
(ii) 2Al + Fe₂ O₃ ⟶ Al₂O₃ + 2Fe - Give the reactions taking place at cathode and anode during the electrolytic refining of copper.
At cathode Cu²⁺ + 2e⁻ → Cu
At anode Cu → Cu²⁺ + 2e⁻ - Name a metal which is commonly used in thermite welding.
Aluminium displaces molten iron from Fe₂O₃ which (Fe) is used in thermite reaction for welding purpose. - An element ‘A’ form two oxides AO and AO₂ . The oxide AO is neutral whereas the oxide AO₂ is acidic in nature. Would you call element ‘A’ a metal or a non-metal?
The element is carbon which is a non- metal. CO is neutral and CO₂ is acidic in nature. - What kind of compounds are called Ionic compounds?Those compounds which are formed between metals and non-metals by transfer of electrons e.g., NaCl, KCl etc.
- Zinc does not evolve hydrogen gas on reacting with HNO₃ . Why?
Because HNO₃ is a strong oxidizing agent which oxidises the generated H₂ to water with zinc and itself is reduced to an oxide of nitrogen. - Which gas is liberated when a metal reacts with an acid? How will you test this gas?
Hydrogen gas is formed. Bring a burning splinter near the gas, it will burn with ‘pop’ sound. - Hydrogen is not a metal but has been assigned a place in the reactivity services of metals. Why?
Like metal, hydrogen also has a tendency to lose electron and forms a positive ion H⁺ therefore it is included in the activity series. - Which of the following listed metals can displace zinc from its salt solution? Give reason for your answer with a chemical equation: Copper, Lead, Magnesium, Silver
Magnesium can displace zinc from zinc salt solution because Mg is more reactive than zinc:
Mg(s) + ZnSO₄ (aq) ⟶ MgSO₄ (aq) + Zn(s) - Out of the two metals P and Q, P is less reactive than Q. Suggest an activity to arrange these metals in the order of decreasing reactivity. Support your answer with a suitable chemical equation.
Add Q in the salt solution of P. If Q is able to displace P’ from its salt solution, then it shows P is less reactive than Q
Q + PR ⟶ QR + P - We can store copper sulphate solution in a silver vessel but not silver nitrate solution in copper vessel. WhyIt is because copper is more reactive than silver, it will displace Ag from AgNO₃ solution. Thus we can’t store AgNO₃ in a copper container but CuSO₄ can be stored in silver vessel as no reaction will take place because silver is less reactive then copper
- List three properties of sodium in which it differs from general physical properties of most metals.
(i) It is soft.
(ii) It has low melting and boiling point.
(iii) It is not malleable and ductile. - Aluminium is highly reactive metal but still used for making cooking utensils. Give reason.
Aluminium reacts with oxygen present in air and forms a thin layer of aluminium oxide on its surface. This oxide layer is very stable and prevents further reaction of aluminium with oxygen. - What are amphoteric oxides? Give two examples. ?
Those metal oxides which react with both acids and bases to produce salt and water are called amphoteric oxides. Amphoteric oxides show both acidic and basic behaviour. Like aluminum oxide (Al₂O₃) and zinc oxide (ZnO). - Write chemical equations that shows aluminium oxide reacts with acid as well base.
"OR"
A metal forms an oxide having formula M₂O₃ . It dissolves both in dilute sulphuric acid as well as dilute sodium hydroxide solution. Identify the metal and write the equations for the reactions involved.
The metal is Al. Its oxide is Al₂O₃.
Al₂ O₃ + 2NaOH ⟶ NaAlO₂ + H₂O
Al₂ O₃ + 3H₂ SO₄ (aq) ⟶ Al₂ (SO₄)₃ (aq) + 3H₂O(l) - Why hydrogen gas is not evolved when a metal reacts with nitric acid?
Hydrogen gas is not evolved when a metals react with nitric acid. Because HNO₃ is a strong oxidizing agent which oxidises the generated H₂ to water and itself is reduced to an oxide of nitrogen. - Why are Food cans coated with tin rather than zinc.
Zinc is more reactive than tin. Due to this, zinc can react with organic acids present in food to form poisonous compounds. To avoid this, the food cans are coated with tin. - Why is copper vessel corroded with a green coating in rainy season ?
When copper vessel is exposed to moist air in rainy season, it reacts with moist carbon dioxide present in the air to form a layer of green colored basic copper carbonate on itself surface. - You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
The sour substances such as lemon or tamarind juice contain acids. These acids dissolve the coating of basic copper carbonate present on the surface of tarnished copper vessels and makes them shining red-brown again. - In one of the methods of rust prevention, iron is not coated with anything. Name that method and define it.
The method is alloy formation (Alloying)
Alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. - What is rust ?
If iron is kept in moist air for a long time, iron reacts with oxygen and water present in the air to form brown colored layer of ferric oxide on itself, which is called rust. - Why sulphide and carbonate ores are converted into oxides?
It is easyer to exrtract metals from their oxide ores by reduction process than their carbonate and sulphide ores. therefore sulphide and carbonate ores are converted into oxides. - Why oxides of highly reactive metals cannot be reduced by carbon ?
Or Why is carbon not used for reducing aluminium oxide to obtain Al?
or Metals placed high in reactivity series cannot be obtained from their compounds by heating with carbon?
Highly reactive metals such as Na, Mg, Ca, Al cannot be obtained from their compounds by heating with carbon. This is because these metals have more affinity for oxygen than carbon. - Define the term ‘anode mud’. Name an electrode made of pure metal.
The insoluble impurities settle down at the bottom of the anode in electrolytic refining are known as anode mud.
In electrolytic refining, cathode is made of pure metal. - The way, metals like sodium, magnesium and iron react with air and water is an indication of their relative positions in the ‘reactivity series’. Is this statement true? Justify your answer with example.
This statement is true.
Na reacts vigorously with cold water because it is highly reactive.
Mg reacts with hard water because it is less reactive than sodium.
Fe reacts only with steam because it is less reactive than magnesium - Name two metals which are purified by electrolytic refining. Mention the cathode, anode and electrolyte used in the refining process. At which electrode would the pure metal be deposited?
Copper, Zinc, Tin, Nickel, Silver, Gold can be purified by electrolytic refining method: In this process, impure metal is made anode and a pure metal is made cathode. Metal salt solutions are used as electrolytes. Pure metal is deposited on the cathode. - Why do ionic compounds have high melting point?
The ionic compounds have the strong force of attraction between positive and negative ions. A large amount of energy is required to break this strong inter-ionic attraction. Therefore Ionic compounds have very high melting and boiling points. - Write four important purposes of making alloys.
To increase the hardness of the substance.
To increase the resistance towards corrosion.
To decrease electrical conductivity
To deceases the melting point. - What is an alloy? How is it prepared? Give two examples of alloys.
Alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.
Alloys are made by first melting the primary metal, and dissolving the other elements in it in definite proportions. It is then cooled to room temperature. - How do properties of iron change when
(i) A small quantity of carbon is mixed in it?
It becomes hard and strong
(ii) Nnickel and chromium are mixed in it?
b. It becomes hard and does not get rusted. - Copper coin is kept immersed in silver nitrate solution for sometime. What change will take place in the coin and in the colour of the solution? Write a balanced chemical equation for the reaction.
When a copper coin is kept immersed in a solution of silver nitrate for some time then the copper coin will get the coating of silver. The solutions colour will turn to blue.
Cu + 2AgNO₃ ⟶ Cu(NO₃)₂ + 2Ag - If a strip of aluminium with scratched clean surface is dipped into an aqueous solution of copper sulphate for a little time, the surface of the strip becomes brownish. What is the reason for this? Write the balanced chemical equation for this.
Aluminium is more reactive than copper So Al displaces less reactive Cu from copper sulphate and forms aluminium sulphate.Copper deposits on the surface of aluminium strip so that it becomes brownish
2Al(s) + 3CuSO₄ (aq) ⟶ Al₂(SO₄ )₃ (aq) + 3Cu(s) - What is formed when sodium absorb moisture from air? Give equation also.
when sodium absorb moisture from air, sodium hydroxide and hydrogen gas is formed:
2Na(s) + 2H₂O(l) ⟶ 2NaOH(aq) + H₂(g) - When a metal X is reacted with cold water, it gives a basic compound Y with molecular formula XOH (Molecular mass 40) and liberates a gas Z which easily catches fire. Identify X, Y, Z.
X is Na (Sodium). , Y is NaOH and Z is H₂ gas
2Na(s) + 2H₂O(l) ⟶ 2NaOH(aq) + H₂ (s)
(Cold) - Write a balanced chemical equation for representing the chemical reaction between manganese dioxide and aluminium powder. What happens if manganese powder is heated with aluminium oxide?
3MnO₂ + 4A1 ⟶ 2Al₂ O₃ + 3Mn
No reaction will take place if manganese powder is heated with Al₂O₃ because Mn is less reactive than Al. - Write a balanced chemical equation for the reaction: Aluminium when heated in air. Write the name of the product formed.
When aluminum is heated in the presence of air, it combines with oxygen to form aluminum oxide.
4Al(s) + 3O₂(g) →Heat→ 2Al₂O₃(S)
Aluminium oxide - A copper plate was dipped into a solution of silver nitrate. After sometime a black layer was observed on the surface of copper plate. State the reason for it and write chemical equation for the reaction involved.
Black layer is deposited due to caoting of silver on the surface of copper plate Because Copper is more reactive than Ag, therefore it displaced Ag from AgNO₃ solution and silver gets deposited on the copper plate
Cu(s) + 2AgNO₃ (aq) ⟶ Cu(NO₃ )₂ (aq) + 2Ag(s) - What happens to potassium and sodium if they are kept in open? Why are they immersed in kerosene oil ?
Potassium and sodium are highly reactive metals. These metals react with oxygen(air) so vigorously that they catch fire when kept in the open. Therefore, they are kept immersed in kerosene oil for safe keeping and to prevent accidental fire. - Aluminium oxide and zinc oxide react with both acids and bases to produce salt and water. What are these oxides called? Write chemical equations in each case.
These are called amphoteric oxides.
Al₂O₃ + 2NaOH ⟶ 2NaAlO₂ + H₂O
Al₂O₃ + 6HCl ⟶ 2AlCl₃ + 3H₂O
ZnO + 2NaOH ⟶ Na₂ZnO₂ + H₂O
ZnO + 2HCl ⟶ ZnCl₂ + H₂O - Suggest a method of reduction for the following metals during metallurgical processes:
(i) Metal A which is one of the last, second or at the third position in the reactivity series.
Reduction with carbon.
(ii) Metal B which gives vigorous reaction even with water and air.
Electrolytic reduction.
(iii) Metal C which is kept in the middle of the activity series.
Reduction with Al. - Suggest different chemical processes used for obtaining a metal from its oxides of metals in the middle of the reactivity series and metals at the top of the reactivity series. Support your answer with one example each.
Metals at the top of activity series are obtained by electrolytic reduction
NaCl ⟶ Na⁺ + Cl⁻
Na⁺ + e– → Na at cathode
2Cl⁻ → Cl₂ + 2e– at anode
Metals in the middle of the reactivity series are obtained by reduction with A1
e.g., Cr₂ O₃ + 2Al ⟶ Al₂ O₃ + 2Cr - A metal P when exposed to moist air for a longer period of time, loses its shining brown surface and attains a green coating; what has happened? Identify the metal, write the name and chemical formula of green coloured compound. List two ways to prevent this process.
(i) This lead to corrosion of copper by formation of green coating of basic copper carbonate on it
(ii) The metal is copper.
(iii)Chemical formula of green coloured compound is basic copper carbonate [CuCO₃.Cu(OH)₂]
(iv) Two ways to prevent this process : Painting, Greasing, Oilin and Galvanizing - From amongst the metal, sodium, calcium, aluminium, copper and magnesium, name the metal:
(i) Which reacts with water only on boiling.
Mg
(ii) Another one which does not react even with steam.
Cu - A metal A which is used in thermite process, when heated with oxygen gives an oxide B which is amphoteric in nature. Identify A and B. Write down the reactions of oxide of B with HCl and NaOH.
A is Aluminium and B is Aluminium oxide
2Al + 3O₂ →Heat→ Al₂O₃(S)
Reactions of aluminium oxide with HCl and NaOH.
Al₂O₃ + 6HCl ⟶ 2AlCl₃ + 3H₂O
Al₂O₃ + 2NaOH ⟶ 2NaAlO₂ + H₂O - predicting the relative activity of various metals ?
The series in which metals are arranged in decreasing order of reactivity is called activity series of metals.
The metal at the top is most reactive, followed by less reactive metal. The metal at the bottom of activity series is least reactive. Thus a metal placed above can displace metal placed below, from its salt solution. - What is reactivity series ? How does the reactivity series of metals help in predicting the relative activities of various metals ?
The series in which metals are arranged in decreasing order of reactivity is called activity series of metals.
The metal at the top is most reactive, followed by less reactive metal. The metal at the bottom of activity series is least reactive. Thus a metal placed above can displace metal placed below, from its salt solution. - State four general properties of ionic compounds.They are soluble in water.They are hard but brittle solids.They do not conduct electricity in solid state but conduct electricity in molten stateThey have high melting and boiling points.
- Compound Z is formed by transfer of electrons from the metal X to a non-metal Y, Identify the type of bond formed in the compound. List three properties of compound formed by such type of bonds.The bond formed is ionic bond:The compound will have high melting and boiling point.It will be soluble in water.It will conduct electricity in molten state as well as in aqueous solution.
- Describe ionic compounds on the basis of following properties:(i) Strong forces of attraction between positive and negative ions.Ionic compounds are hard and they have high melting and boiling points(ii) Solubility of compounds in water.They are soluble in water.(iii) Electrical conductivity.They do not conduct electricity in solid state but conduct electricity in molten state
- Why do ionic compounds conduct electricity in molten state and not in solid state?Ionic compounds conduct electricity in molten state because ions are present in aqueous solution of ionic compounds. When an electric current is passed through the solution, these ions start moving towards the opposite electrode and conduct electricity. Ionic compounds do not conduct electricity in solid state because movement of ions is not possible in solid state due to rigid structure.
- What will you observe when:
(i) Some zinc pieces are placed in copper sulphate solution.
The solution will become colourless, reddish brown because more reactive zinc displaces less reactive Cu from its compound.
Zn(s) + CuSO₄ (aq) ⟶ ZnSO₄ (aq) + Cu(s)
(ii) Some silver pieces are placed into green coloured ferrous sulphate solution.
No reaction will take place because Ag is less reactive than Fe. - Define the terms: (i) Mineral (ii)Ores (iii) Gangue
Mineral: The elements or compounds, which occur naturally in the earth’s crust, are known as minerals. e.g., Mica.
Ores - These minerals which contain a very high percentage of a particular metal and the metal can be profitably extracted from it are called ores. e.g., Haematite.
Gangue -The impurities present in the ore is called gangue e.g., SiO₂ - Name the ore of mercury. How mercury is extracted from its ore?
The ore of mercury is cinnabar (HgS).
Roasting : When cinnabar (HgS) is heated in air, it gets converted into mercuric oxide.
2HgS(s) + 3O₂(g) → Heating → 2HgO(l) + 2SO₂(g)
Mercuric sulphide mercuric oxide
Self-Reduction: On heating mercuric oxide further, it gets reduced to mercury.
2HgO → Heating → 2Hg + O₂ - How is copper obtained from Cu₂S? Give reactions
Copper which is found as Cu₂S in nature can be obtained from its ore by just heating in air.
Roasting:
Cu₂S(s) + 3O₂ (g) → Heating → 2Cu₂O(s) + SO₂ (g)
Self-Reduction:
2Cu₂O(s) + Cu₂S(s) → Heating → 6Cu(s) + SO₂(g) - How metals can be differentiated from non-metals on the basis of any of it three chemical roperties ?
(i) Metallic oxides are basic in nature. while non-metallic oxides are acidic in nature
(ii) Most of metals displace hydrogen from dilute acids. while non-metals do not displace hydrogen from dilute acids.
(iii) Only few of the metals combine with hydrogen to form ionic hydrides. while non-metals combine with hydrogen to form covalent hydrides. - State the conditions under which the following metals react with water. Write chemical equation for its reaction with each: (i) Na (ii) Mg (iii) Fe
(i) Na - Sodium metal reacts with cold water as:
2Na + 2H₂ O ⟶ 2NaOH + H₂
(ii) Mg - Magnesium reacts with hot water as:
Mg + 2H₂ O ⟶ Mg(OH)₂ + H₂
(iii)Fe - Iron reacts with steam as:
3Fe + 4H₂ O ⟶ Fe₃ O₄ + 4H₂ - Write chemical equations for the reactions taking place when:
(i) Lead carbonate is calcined.
PbCO₃(s) ⟶ Heat⟶ PbO(s) + CO₂ (g)
(ii) Chromium oxide (Cr₂O₃ ) is heated with aluminium powder.
Cr₂O₃(s) + 2Al(s) ⟶ Heat ⟶ Al₂O₃ (s) + 2Cr(l)
(iii) Aluminium powder is added to Fe₂O₃.
2A1 + Fe₂ O₃ ⟶ Al₂O₃ + 2Fe
(iv) Zinc sulphide is roasted.
2ZnS + 3O₂ ⟶ 2ZnO + 2SO₂ - A, B and C are three elements which undergo chemical reactions according to the following equations:
A₂O₃ + 2B ⟶ B₂O₃ + 2A
3CSO₄ + 2B ⟶ B₂(SO₄)₃ + 3C
3CO + 2A ⟶ A₂O₃ + 3C
(i) Which element is most reactive?
B is most reactive.
(ii) Which element is the least reactive?
C is least reactive.
(iii) What type of reactions is listed above?
Displacement reactions. - (i) What type of ores are calcined? Illustrate with suitable examples.
Carbonate ores are calcined e.g., ZnCO₃ → Heating → ZnO+ CO₂
(ii) In what form calcined ore is obtained and how it can be reduced? Give chemical equation for the reduction process involved for the example given by you.
It is obtained in oxide form.
It is reduced by using a suitable reducing agent
ZnO + C → Heating → Zn + C - Using the electronic configuration, explain how magnesium atom combines with oxygen atom to form magnesium oxide by transfer of electrons.
Formation of Magnesium chloride
Mg → Mg²⁺ + 2e⁻
2,8,2 2,8
Cl + 2e⁻ → Cl⁻
2,8,7 2,8,8 - Explain the formation of ionic compound CaO with its electron dot structure. Atomic number of Ca = 20, O = 8.
Ca → Ca²⁺ + 2e-
2,8,8,2 2,8,8
O + 2e- → O²⁻
2,6 2,8 - Na → Na⁺ + e-Write the electron dot structure for sodium and chlorine atoms. How do these atoms form a chemical bond? Name the type of bond so formed. Why does a compound so formed have high melting point. ?
2,8,1 2,8
Cl + e- → Cl⁻
2,8,7 2,8,8
Sodium can lose an electron and Cl gains that electron and they form an ionic bond. It has high melting point due to strong forces of attraction between Na⁺ and Cl⁻ ions. - (i) Name the ions present in the compound, CaS. Atomic number of Ca = 20, S = 16
(ii) Write the electron dot structure of Calsium and Sulphide.
(iii) Show the formation of CaS by transfer of electrons.
(i) Calsium [Ca²⁺] and Sufide [F⁻] ions are present in the compound, CaS.
(ii) Electron dot structure of Calsium and Sulphide.
(iii) formation of CaS
Ca → Ca²⁺ + 2e-
2,8,8,2 2,8,8
S + 2e- → S²⁻
2,8,6 2,8,8 - (i) Write the electron dot structure of Potassium (19) and Chlorine (17).
(ii) Name the ions present in the compound, KCl.
(iii) Show the formation of KCl by transfer of electrons.
(i) Electron dot structure of Potassium and Chlorine
(ii) K⁺ and Cl⁻ ions are present in the compound, KCl.
(iii) Formation of Kalcium chloride
K → K⁺ + e⁻
2,8,8,1 2,8,8
Cl + 2e⁻ → Cl⁻
2,8,7 2,8,8 - (i) Write electron dot structure of Potassium and Chlorine
(ii) Name the ions present in the compound, KCl.
(iii) Show the formation of KCl by transfer of electrons.
(i) Electron dot structure of Potassium and Chlorine
(ii) K⁺ and Cl⁻ ions are present in the compound, KCl.
(iii) Formation of Kalcium chloride
K → K⁺ + e⁻
2,8,8,1 2,8,8
Cl + 2e⁻ → Cl⁻
2,8,7 2,8,8 - Write electron dot diagrams of chlorine (At. No. 17) and calcium (At. No. 20). Show the formation of calcium chloride by transfer of electrons.
Formation of Magnesium chloride
Ca → Ca²⁺ + 2e⁻
2,8,8,2 2,8,8
Cl + 2e⁻ → Cl⁻
2,8,7 2,8,8 - Show the formation of Na₂O by transfer of electrons between the combining atoms.
formation of Na₂O
Na → Na⁺ + e-
2,8,1 2,8,
O + 2e- → O²⁻
2,6 2,8 - State three reasons for the following facts: One of the reason must be supported with a chemical equation.
(i) Sulphur is a non-metal.
Sulphur is a non-metal because it reacts with O₂ to form SO₂ which is an acidic oxide:
S + O₂ ⟶ SO₂
Sulphur is not malleable and ductile
Sulphur is not malleable and ductile
(ii) Magnesium is a metal.
Manesium is a metal which reacts with O₂ to form basic oxide:
2Mg + O₂ ⟶ 2MgO
Magnesium is malleable and ductile.
Magnesium conducts electricity - Why does calcium float in water?
Or
Explain, why calcium metal after reacting with water starts floating on its surface. Write the chemical equation for the reaction.
Calcium form hydrogen gas on reaction with water. The bubbles of hydrogen gas sticks to the surface of calcium metal. and that is why calcium floats in water.
Ca(s) + 2H₂O(l) ⟶ Ca(OH)₂(aq) + H₂ (g) - A substance X which is an oxide of metal is intensively used in cement industry. The element is present in our bones also. On treatment with water, it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.
X is calcium. Its oxide, CaO is used in cement industry. Calcium is also present in bones.
Ca(s) + 2H₂O(l) ⟶ Ca(OH)₂ (aq) + H₂ (g)
Calcium hydroxide turns red litmus blue. - Differences between calcination and roasting.
Roasting-
1. Roasting is a process of heating sulphide ore at high temperature in the presence of excess air.
2. Roasting is used to convert sulphide ore into oxide.
3. Ex. 2ZnS+ 3O₂ → Heating → 2ZnO+ 2SO₂
Calcination-
1. Calcination is a process of heating Carbonate ore at high temperature in the presence limited amount of air.
2. Calcination is used to convert oxide ore into sulphide.
3. Ex. ZnCO₃ → Heating → ZnO+ CO₂ - Explain the process by which metal is obtained from its molten chloride
Metals are obtained from their molten chlorides by the process of electrolytic reduction. ‘Na’ metal is obtained by electrolysis of molten NaCl
Metals are obtained from their molten chlorides by the process of electrolytic reduction. ‘Na’ metal is obtained by electrolysis of molten NaCl
Electrolysis of sodium chloride:
In this process, impure metal is made anode and a thin layer of pure metal is made cathode. Metal salt solutions are used as electrolytes. When current is passed through the electrolyte, the electrolyte separates into sodium and chloride ions.The impure metal at the anode dissolves in the electrolyte. And an equal amount of pure metal is deposited on the cathode .
Electrolysis of NaCl
NaCl ⟶ N⁺ + Cl⁻
At cathode: Na⁺ + e- ⟶ Na
At anode: 2Cl⁻ → Cl₂ + 2e⁻
- Four metals A, B, C and D are added to the following aqueous solutions one by one. The observations made are tabulated below:
Answer the following questions based on the above observations:Metal
Iron sulphate
Copper sulphate
Zinc sulphate
Silver nitrate
A
No reaction
Reddish Brown Dep.
…………..............
…………................
B
Grey Deposit
………..................
No reaction
………...................
C
No reaction
No reaction
No reaction
White Shining Dep.
D
No reaction
No reaction
No reaction
No reaction
D Ag C Cu A fe B Zn
(i) Which is the most active metal and why?
B is the most reactive because it displaces Fe. It will displaces Fe. It will displace Cu as well as Ag also.
(ii) What would be observed if B is added to copper (II) sulphate solution and why?
B will displace copper from CuSO₄ solution because it is more reactive than Cu.
(iii) Arrange the metals A, B, C and D in order of increasing reactivity.
D is least reactive and D<C<A<B is the increasing order of reactivity.
(iv) Container of which metal can be used to store both zinc sulphate solution as well as silver nitrate solution?
Container of metal D can be used to store both ZnSO₄ and AgNO₃ .
(v) Which of the above solutions can be easily stored in a container made up of any of these metals?
Zinc sulphate solution can be stored in container made up any of the metals A, B, C, D because none of them could displace zinc from zinc sulphate as these are less reactive than zinc.
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