Table of Contents

Definition

Metallurgy class 10 questions and answers

Minerals: The naturally occurring metallic compounds found in Earth’s crust are called minerals.

EX – Gibbsite [ Al (OH)₃] is a mineral of aluminium.

Ores: The minerals from which a particular metal can be extracted conveniently and economically are called ores of that particular metal.

EX – From Bauxite ( Al₂O₃ . 2H₂O )aluminium can be extracted conveniently and profitably. Hence, Bauxite is called an ore of aluminium.

Metallurgy: The various processes involved in the extraction of metals from their ores and refining are called metallurgy.

Oxidation: Oxidation is a process where an atom or ion loses an electron(s), i.e., oxidation involves loss of electron(s).

EX – When atoms of elements lose electron(s) and are converted into their cations these atoms are said to be oxidised.

Na – e → Na⁺ ; Ca – 2e → Ca²⁺

Reduction: Reduction is a process in which an atom or ion gains electron(s), i.e., reduction involves the gain of electron(s).

EX – When metal ions like Fe ³⁺, Al³⁺ etc. are converted to their corresponding metal atoms by gaining electron(s), these ions are said to be reduced.

Al³⁺ + 3e → Al ; Fe³⁺ + 3e → Fe

Thermite Mixture: A mixture of 3 parts of ferric oxide and 1 part of aluminium powder is called a thermite mixture.

Activity series of metals: The reactivity of all the metals are not the same. The arrangement of metals in a vertical column in the order of decreasing reactivities is called the activity series of metals.

Corrosion: The deterioration of metals by the action of air, moisture, etc. is called corrosion.

Write a note on Iron: –

Iron

Symbol: Fe

Valency: 2 and 3

Atomic Weight: 55.85

Chief Ore: Haematite ( Fe₂O₃)

Properties of Iron:

Physical Properties:

Pure iron is a bright white metal.

Iron is a comparatively heavy metal. Its density is 7.874 g.cm^-3 ( near room temperature).

The melting point of iron is 1539°C.

Iron is a malleable and ductile metal.

Iron is attracted by a magnet and it can be magnetised also.

Chemical Properties:

Ⅰ Reaction with air:

ⅰ. Iron does not react with dry air.

ⅱ. At ordinary temperature and in presence of moist air, a reddish-brown flakey coating is observed on the surface of the iron. This is called rust. Rust is a hydrated ferric oxide ( Fe₂O₃ . x H₂O ). Rust is not formed on pure iron.

ⅲ. In presence of air or oxygen when the iron is heated strongly iron burns with a shower of sparks to form ferrosoferic oxide ( triferric tetraoxide).

3 Fe +2 O₂= Fe₃O₄

Ⅱ Reaction with water:

ⅰ. At normal temperature, iron does not react with water.

ⅱ. When steam is passed over red-hot ( 600°C – 800°C) iron, ferrosoferric oxide and hydrogen gas are produced.

3Fe +4H₂O ( vapour ) = Fe₃O₄ + 4 H₂ ↑

Ⅲ Reaction with acids:

ⅰ. When iron reacts with dilute or concentrated HCl, ferrous chloride and hydrogen gas are produced.

Fe + 2 HCl = FeCl₂ + H₂ ↑

ⅱ. Iron reacts with dilute H₂SO₄ to produce ferrous sulphate and hydrogen gas.

Fe + H₂SO₄ = FeSO₄ + H₂ ↑

Iron reacts with hot and concentrated H₂SO₄ to produce ferric sulphate, sulphur dioxide gas and water.

2Fe + 6H₂SO₄= Fe(SO₄)₃ + 3SO₂ ↑ + 6H₂O

ⅲ. Cold and dilute HNO₃ reacts with iron to produce ferrous nitrate and ammonium nitrate.

4Fe +10HNO₃ = 4Fe(NO₃)₂+ NH₄NO₃ + 3H₂O

Hot and concentrated HNO₃reacts with iron to produce ferric nitrate and reddish-brown coloured nitrogen dioxide gas.

Fe + 6HNO₃ = Fe(NO₃)₃+ 3NO₂↑ + 3H₂O

Extremely concentrated or fuming HNO₃does not react with iron because it transforms iron into passive iron, by forming an insoluble thin coating of Fe₂O₃ on the surface of the iron.

Ⅳ Reaction with alkali: Iron does not react with any alkali.

Ⅴ Displacement reaction: Iron can replace the metals which are placed below iron in the electrochemical series. For example, when the iron is added to the aqueous solution of copper sulphate then iron displaces copper from copper sulphate solution to form ferrous sulphate and metallic copper which is precipitated.

CuSO₄ + Fe = FeSO₄ + Cu ↓

Ⅵ Reaction with non-metals: Red hot – iron reacts with chlorine, sulphur and carbon to form ferric chloride, ferrous sulphide and iron carbide respectively.

2Fe + 3Cl₂ = 2FeCl₃

Fe + S = FeS

3Fe + C = Fe₃C

Passive Iron

When iron is dipped in highly concentrated or fuming nitric acid, an impervious coating is formed on the surface of the iron. As a result, acid cannot come in contact with iron anymore. This iron is known as passive iron. In this inert state, iron loses its general properties. This can be removed by strong heating of the metal.

Rust: Reddish-Brown coating of hydrated ferric oxide deposited on iron when left exposed to moist air at ordinary temperature is called Rust.

The formula of Rust: The formula of rust is Fe₂O₃. x H₂O

Conditions necessary for rusting: The conditions necessary for rusting are the presence of

Oxygen or Air
Moisture or Water Vapour

Classification of Iron: The different kinds of iron are :

Cast Iron
Steel
Wrought Iron

Uses of Iron:

Use of Cast Iron: Cast Iron is used to prepare railings, pipes, light posts, cauldrons etc.

Use of Steel: It is used to make knives, scissors, blades, surgical instruments, rails, tram lines, ships, tractors, permanent magnets, bridges, springs of automobiles, etc.

Use of Wrought Iron: Wrought Iron is used to make wires of iron, small iron chains, nails, nuts, bolts, electromagnets, etc.

Stainless Steel

The alloy of steel which is made by mixing 18% of chromium, 8% of nickel with steel is known as stainless steel. As, it never rusts, so it is called stainless steel.

Two alloys of iron along with their composition and uses:-

Note on Copper

At normal temperature, copper does not react with dry air.

In moist air, black oxides and sulphides of copper are formed. If left for a long period, these compounds are ultimately converted into basic copper sulphate [ CuSO₄. 3Cu( OH)₂ ]. Then the layer looks green.

If copper is heated strongly in dry air or oxygen, then black cupric oxide and red coloured cuprous oxides are formed.

2Cu + O₂ = 2CuO ; 4Cu + O₂ = 2 Cu₂O

Cupric Oxide Cuprous Oxide

Reaction with Water: Copper does not react with water or steam.

Reaction with Acids:

Ⅰ. Since the position of copper is below hydrogen in the electrochemical series, so copper does not react with dilute HCl or dilute H₂SO₄i.e., copper cannot displace hydrogen from HCl or H₂SO₄as it is less reactive than hydrogen.

But in presence of air or oxygen, copper reacts with conc. HCl and dilute H₂SO₄to form copper chloride and copper sulphate respectively.

2Cu + 4HCl +O₂= 2CuCl₂ + 2H₂O

2Cu + 2H₂SO₄+ O₂ = 2CuSO₄ +2H₂O

Ⅱ. Copper reacts with hot and concentrated H₂SO₄to form copper sulphate, water and sulphur dioxide gas.

Cu + 2H₂SO₄ = CuSO₄+ SO₂ ↑ + 2H₂O

Ⅲ. Copper reacts with cold and dilute HNO₃ to form copper nitrate, water and nitrous oxide gas.

4Cu + 10HNO₃ = 4Cu(NO₃)₂ + N₂O↑ + 5H₂O

But cold and moderate (1:1) HNO₃ reacts with copper to form cupric nitrate, water and nitric oxide gas.

3Cu + 8HNO₃= 3Cu(NO₃)₂+ 2NO↑ + 4H₂O

Copper reacts with hot and concentrated HNO₃to form cupric nitrate, water and nitrogen dioxide gas.

Cu + 4HNO₃ = Cu(NO₃)₂+ 2NO₂↑ + 2H₂O

When HNO₃ vapour is passed over heated copper, cupric oxide, nitrogen gas and water are produced.

5Cu + 2HNO₃ = 5CuO + N₂ ↑ + H₂O

Reaction with alkali: Copper does not react with any alkali.

Reaction with Halogens: Copper combines with halogens directly to form corresponding halides.

Cu + Cl₂ →CuCl₂

Cu + Br₂→ CuBr₂

Cu + I₂ →CuI₂

Moist chlorine rapidly attacks copper even at ordinary temperature.

Reducing property: Copper reduces oxides of nitrogen to elementary nitrogen and ferric ion to ferrous ion.

2Cu + 2NO = 2CuO + N₂

2FeCl₃+ Cu = Cucl₂ + 2FeCl₂

Displacement Reactions: Copper displaces silver and mercury from their salt solutions.

2AgNO₃+ Cu = 2Ag+ Cu(NO₃)₂

HgCl₂ + Cu = CuCl₂ + Hg↓

Uses of Copper :

Ⅰ. Being a good conductor of electricity, copper is used to make electrical wires, dynamos, motors, transformers and other electrical appliances.

Ⅱ. Being a good conductor of heat, copper is used to make cooking utensils, calorimeters, boilers, etc.

Ⅲ. Copper is used in electroplating, electrotyping and in electric cells.

Ⅳ. Copper is used in the preparation of alloys like brass, bronze, bell metal, german silver etc.

Two alloys of copper along with their composition and uses.

Note on Zinc( Zn )

Zinc:

Symbol: Zn

Valency: 2

Atomic Weight: 65.3

Chief Ore: Zinc Blende( ZnS)

Physical properties of Zinc:

Ⅰ. Zinc is a bluish-white metal. It acquires grey colour when exposed to moist air.

Ⅱ. Density of Zinc is 7.14 g.cm^-3 ( near room temperature ).

Ⅲ. The melting point of zinc is 419.5°C and the boiling point of zinc is 907°C.

Ⅳ. Zinc is a good conductor of heat and electricity.

Ⅴ. At normal temperature and at a temperature of more than 200°C zinc is bristle but between 110°C to 150°C zinc is malleable and ductile.

Chemical properties of zinc:

Ⅰ. Reaction with air:

ⅰ. Zinc does not react with dry air.

ⅱ. In moist air, zinc reacts to form a white coating of basic carbonate [ ZnCO₃. 3Zn(OH)₂ ] on zinc which fades the normal brightness of zinc.

ⅲ. When zinc is heated in air or oxygen, it burns with white flame and produces white fumes of zinc oxide. This zinc oxide vapour gets cooled and condensed to form woolly flocks known as Philosopher’s wool or zinc white.

2Zn + O₂ = 2ZnO

Ⅱ. Reaction with water:

ⅰ. Pure zinc does not react with water.

ⅱ. When steam is passed over red – hot zinc, zinc oxide and hydrogen gas are formed.

Zn + H₂O = ZnO + H₂ ↑

Ⅲ. Reaction with acids: Pure zinc is attracted slowly by acids but commercial zinc reacts readily with all acids.

ⅰ. Zinc reacts with both dilute and concentrated HCl to form zinc chloride and hydrogen gas.

Zn + 2 HCl = ZnCl₂+ H₂ ↑

ⅱ. Zinc reacts with dilute H₂SO₄to form zinc sulphate and hydrogen gas.

Zn + H₂SO₄ = ZnSO₄+ H₂ ↑

Zinc reacts with hot and concentrated H₂SO₄ to form zinc sulphate, sulphur dioxide and water.

Zn + 2H₂SO₄= ZnSO₄ + SO₂ ↑+ 2H₂O

(concentrated)

ⅲ. When zinc reacts with very dilute and cold HNO₃, zinc nitrate, ammonium nitrate, and water are formed.

4Zn + 10 HNO₃ = 4Zn(NO₃)₂ + NH₄NO₃+ 3H₂O

(very dilute)

When zinc reacts with dilute and cold HNO₃, zinc nitrate, nitrous oxide and water are formed.

4Zn + 10 HNO₃ = 4Zn(NO₃)₂ +N₂O↑+ 5H₂O

When zinc reacts with cold and moderate (1:1) HNO₃, zinc nitrate, nitric oxide and water are formed.

3Zn + 8HNO₃ = 3Zn(NO₃)₂ + 2NO ↑+ 4H₂O

moderate(1:1)

When zinc reacts with hot and concentrated HNO₃, zinc nitrate, NO₂gas and water are formed.

Zn + 4HNO₃ = Zn(NO₃)₂ + 2NO₂↑+ 2H₂O

Ⅳ. Reaction with alkalis: When zinc is heated with the concentrated solutions of caustic soda or caustic potash solution, soluble sodium zincate or potassium zincate salts are produced respectively.

Zn + 2 NaOH = Na₂ZNO₂+ H₂↑

Zn + 2 KOH = K₂ZnO₂+ H₂↑

Ⅴ. Displacement Reaction: Zinc displaces metals from the aqueous solution of salts of less active metals. For example – When zinc is added to the aqueous solution of salts of less active metals. For example – When zinc is added to an aqueous solution of copper sulphate, zinc sulphate is formed and reddish-brown coloured copper is precipitated.

CuSO₄+ Zn = ZnSO₄ +Cu↑

Ⅵ.Reducing property: When zinc dust is added to an acidified solution of yellow coloured ferric sulphate solution ( acidified with dilute sulphuric acid ) then yellow coloured ferric sulphate is reduced to colourless ferrous sulphate by zinc.

Fe₂(SO₄)₃+ Zn = 2 FeSO₄ + ZnSO₄

Ⅶ. Reaction with non-metals:

ⅰ. Zinc reacts with halogens directly to form respective zinc halides.

Zn + X₂= ZnX₂ [ X may be F, Cl, Br, I ]

ⅱ. When zinc is heated with sulphur, it forms zinc sulphide.

Zn + S = ZnS

Ⅷ. Reaction with ammonia: Zinc reacts with ammonia in presence of heat to form zinc nitride and hydrogen gas.

3Zn +2NH₃ = Zn_,3N₂+ 3H₂↑

Ⅸ. Uses of Zinc:

ⅰ. To protect iron articles from rusting, a thin coating of zinc is applied on the surfaces of those articles.

ⅱ.Zinc is used in the preparation of dry cells and other electric cells.

ⅲ. Zinc is used to prepare white paint called zinc white, hydrogen in the laboratory and also in the extraction of metals like gold, silver, etc.

ⅳ. Zinc is also used in making some alloys like brass, german silver, etc.

Two alloys of zinc along with their composition and uses:-

Ⅹ. Philosopher’s wool or Zinc White: Zinc Oxide is known as Philosopher’s wool or zinc white. It is used as white paint.

2Zn +O₂= 2ZnO

ⅩⅠ. Galvanisation: To protect iron articles from rusting, a coating of zinc is applied on the surface of those articles. This process is known as Zinc plating or Galvanisation.

Note on Aluminium(Al):

Aluminium:

Symbol: Al

Valency: 3

Atomic Weight: 26.98

Chief Ore: Bauxite(Al₂O₃. 2H₂O)

Physical properties:

Ⅰ. Aluminium is a silvery-white lustrous metal. The lustre is destroyed on long exposure to air due to the formation of a thin film of oxide on the surface.

Ⅱ. Density of aluminium is 2.70 g.cm^-3( near room temperature )

Ⅲ. The melting point of aluminium is 660.32°C and its boiling point is 2519°C.

Ⅳ. Aluminium is a good conductor of heat and electricity.

Ⅴ. Aluminium is malleable and ductile.

Chemical properties:

Ⅰ.Reacction with air:

ⅰ. Dry air has no action on aluminium.

ⅱ. In moist air, a thin film of aluminium oxide is formed on the surface of aluminium which protects it from further action with air.

ⅲ. Aluminium powder, wire or plate when heated strongly in air burns with bright white flame. It reacts with oxygen and nitrogen present in the air to produce aluminium oxide and aluminium nitride respectively.

4Al +3 O₂= 2Al₂O₃ ; 2Al + N₂ = 2AlN

Ⅱ.Reaction with water:

ⅰ. Aluminium does not react with cold water at normal condition.

ⅱ. Aluminium powder reacts with boiled water to form hydrogen and aluminium hydroxide.

2Al + 6H₂O ↔ 2Al(OH)₃ + 3H₂↑

Ⅲ. Reaction with Acids:

ⅰ. Aluminium reacts with cold and dilutes HCl to produce aluminium chloride and hydrogen gas. If the acid is concentrated and hot then the reaction becomes intense.

2Al + 6HCl = 2AlCl₃ + 3H₂ ↑

ⅱ. Aluminium reacts with cold and dilutes H₂SO₄to produce aluminium sulphate and hydrogen gas.

2Al + 3H₂SO₄= Al₂(SO₄)₃ + 3H₂↑

It also reacts with concentrated and hot H₂SO₄ to produce aluminium sulphate and sulphur dioxide gas.

2Al + 6H₂SO₄= Al₂(SO₄)₃ + 3 SO₂ ↑+ 6H₂O

ⅲ. Aluminium does not react with dilute or concentrated nitric acid as nitric acid is a strong oxidising agent. Thus, nitric acid renders aluminium unreactive due to the formation of a thin insoluble protective layer of aluminium oxide. In presence of impurities, aluminium reacts very slowly with dilute HNO₃ to produce aluminium nitrate and ammonium nitrate.

Ⅳ. Reaction with alkalis: Aluminium powder, when boiled with caustic soda or caustic potash solution, sodium illuminate or potassium aluminate salts and H gas is produced.

2Al + 2NaOH + 2H₂O = 2NaAlO₂ + 3H₂↑

2Al + 2KOH + 2H₂O = 2KAlO₂ + 3H₂↑

Ⅴ. Reducing Property: At higher temperatures, aluminium acts as a reducing agent. At a high temperature, aluminium reduces ferric oxide , chromium oxide and manganese dioxide to metallic iron , chromium and manganese respectively.

2Al + Fe₂O₃= Al₂O₃ + 2Fe

2Al + Cr₂O₃,= Al₂O₃ + 2Cr

8Al + 3Mn₃O₄= 4Al₂O₃ + 9Mn

Ⅵ. Reaction with non-metals: Besides oxygen, aluminium reacts with non-metals to form corresponding compounds.

ⅰ. Aluminium when heated in the atmosphere of nitrogen, forms aluminium nitride.

2Al + N₂ = 2 AlN

ⅱ. The aluminium powder when fused with sulphur forms aluminium sulphide.

2Al + 3S = Al₂S₃

ⅲ. Finely powdered, heated aluminium, combines with halogens to form corresponding halides.

2Al + 3X₂ = 2AlX₃( X= F,Cl,Br,I )

Ⅶ. Displacement Reactions: Being more electropositive, aluminium displaces copper, zinc and lead from the solution of their salts.

3ZnSO₄ + 2Al = Al₂(SO₄)₃ + 3Zn

3CuSO₄ + 2 Al = Al₂(SO₄)₃ + 3Cu

Ⅷ. Uses of Aluminium:

ⅰ. Aluminium is used in the making of aircraft and motor car bodies.

ⅱ. Aluminium is widely used in making cooking utensils and furniture.

ⅲ. Being a good conductor of electricity, aluminium is used for making electrical wires and other appliances.

ⅳ. Aluminium foils are used for packing medicines, foodstuffs, chocolates, etc.

Two alloys of aluminium along with their compositions and uses:

Short Questions:

What do you mean by alloy?

ANS: A homogenous mixture of two or more than two metals and non-metals is known as an alloy.

Ex- An example of an alloy is brass which is produced by mixing copper and zinc.

Write down the importance of alloys?

OR,

What are the advantages of using alloys instead of metals?

ANS: I. Alloys are much harder than their constituent metals.

Ex: Copper is a soft metal but its alloy bell metal or brass are harder than copper.

ⅱ. The melting point of an alloy is less than the melting point of its constituent metals.

Ex: The melting point of soldering metal ( Pb + Sn ) is less than that of its component elements lead and tin.

ⅲ. To protect from corrosion by the action of water or moisture and air, alloys are used instead of metals.

Ex: In moist air, iron rusts but its alloy stainless steel does not rust.

ⅳ. Alloys are more malleable and ductile than ordinary metals and for this reason, alloys are widely used.

Ex: Alnico, an alloy of iron can withstand two times of its own weight.

ⅴ. Alloys have less tendency to be oxidized than their component elements.

ⅵ. To increase or decrease thermal and electrical conductivities, alloys are used.

Why aluminium is used as cooking utensils?

ANS: Aluminium is a good conductor of heat. It does not react with water. It is also cheap and light. That is why aluminium is used as cooking utensils.

What is the formula of sodium aluminate?

ANS: NaAlO₂

What is the chemical name and formula of baking powder?

ANS: Chemical Name: Sodium bicarbonate

Formula: NaHCo₃

What is the chemical name and formula of caustic soda?

ANS: Chemical Name: Sodium hydroxide.

Formula: NaOH

What is the chemical name and formula of caustic potash?

ANS: Chemical name: Potassium hydroxide

Formula: KOH

State what happens when steam is passed over red-hot iron.

ANS: When steam is passed over red-hot iron, ferrosoferric oxide and H₂ gas are formed.

3Fe + 4H₂O = Fe₃O₄ + 4H₂↑

Why is copper used as an electrical appliance?

ANS: Copper is a good conductor of electricity. It has less resistance, that is why copper is used as an electrical appliance.

Name a metal that reacts both with an acid and an alkali to produce salt and hydrogen.

ANS: Aluminium.

What is Philosopher’s wool?

ANS: When zinc is burnt in air or oxygen, white zinc oxide vapour forms. This vapour of zinc oxide when cools and condenses look like wool, which is called Philosopher’s Wool.

2Zn + O₂ = 2ZnO

State whether pickles should be taken in aluminium foil or not. Give reasons.

ANS: Pickle contains vinegar ( acetic acid ) which is an organic acid. This organic acid reacts with aluminium foil to produce aluminium acetate which is harmful to our health. Thus, the pickle should not be wrapped in aluminium foil.