Copper [Cu]

Main ores of copper

• Copper iron pyrite or chalcopyrite = CuFeS₂
• Cuprite = Cu₂O
• Copper glance = Cu₂S
• Malachite = Cu(OH)₂·CuCO₃
• Azurite = 2CuCO₃·Cu(OH)₂

Extraction of Copper

Specially copper is extracted by copper iron pyrite including following process.

1. Concentration

The big lumps of CuFeS₂ is first crushed and grinded into fine powder then concentrated by froth floating process.

2. Roasting

In this process, concentrated ore are strongly heated in reverberatory furnace then impurities are removed as their oxide and CuFeS₂ is converted into ferrous oxide and cuprous oxide.

Reaction of impurities:

Rxn in CuFeS₂:

3) Reduction

a) Smelting

For this process, roasted ore are mixed with coke and sand (SiO₂) then placed in blast furnace and heated by hot air blow. The FeO combines with silica and form slag.

The copper oxide is also converted into the cuprous sulphide.

The molten mass below the slag is mixture of cuprous sulphide and FeS is known as matte (coarse metal) then removed out.

b) Bessemerization

Thus obtained matte is placed in egg-shaped Bessemer’s converter having internal lining acidic or basic medium depending upon nature of impurities. Due to the hot air blast following rxn occurs.

The molten mass of copper is poured off from converter and allowed to cool. At the metal solidifies, the dissolved SO₂ escape out and give the shape of blister to the surface of solidified copper, so the product is known as blister of copper.

4) Purification [Electrolytic refining]

For the purification of copper impure copper or blister copper made an anode and thin sheet of pure copper made a cathode and copper sulphate soln as electrolyte. When electricity is passed then pure copper is deposited on cathode and following rxn occurs.

At anode:

At cathode:

Properties of Copper

1) Action with air

In moist air copper gets corroded by following green film of basic carbonate on its outer surface.

2) Action with acids

a) Dilute H₂SO₄ and HCl

Cu reacts with dil. H₂SO₄ and HCl at hot condition only in presence of air.

b) With conc. H₂SO₄ and HCl

Cu reacts with conc HCl in presence of air.

Cu react with conc. H₂SO₄ then released SO₂ gas in presence of heat.

c) Action with HNO₃

Moderate conc. HNO₃ (1:1) react with copper in cold condition to give NO but conc. HNO₃ gives NO₂ gas.

Uses of Copper

• It is used in making utensils.
• It is used in making conducting wires.

Compounds of Copper

A. Cuprous oxide or red oxide [Cu₂O] and cupric oxide or black oxide [CuO]

Preparation

Properties

1) Action with heat

When Cu₂O is heated at 1200°C it reacts with air to give black oxide.

When CuO is heated above 1100°C, it gets decomposed.

2) Action with HCl

Conc HCl combines with both oxide i.e. red and black oxide and gives salt and water.

3. Action with H₂

Cu₂O is not reduced by hydrogen at any condition but CuO is reduced by hydrogen at hot condition.

Uses

For Cu₂O

• It is used in red coloration of red stained glass.
• It is used in painting to avoid rusting.
• It is used in the preparation of other compounds of Cu.

For CuO

• It is used in the manufacture of light blue colored glass.
• It is used as the detector of hydrogen present in organic compound.
• It is used in preparation of other compound of Cu.

B. Blue Vitriol [CuSO₄·5H₂O] / Nilathutha

Preparation

1. Copper sulphate is prepared by treating CuO, Cu(OH)₂ and CuCO₃ with dil H₂SO₄.

2) Copper sulphate can be prepared by heating Cu-turning with hot and dil H₂SO₄ in presence of air.

Thus obtained CuSO₄ dissolved in H₂O and then heated up to crystallization point to get crystals of CuSO₄·5H₂O.

Properties

• Blue vitriol is blue crystalline solid and anhydrous one is white powder.
• It is slightly acidic in nature.
• It is readily soluble in water.

4) Action with heat

On heating to different levels of temp at 100°C its water of crystallization successively and finally gets decomposed to give black oxide of copper.

5. Action with ammonia solution

6) Action with potassium iodide solution

Copper sulphate combines with potassium iodide by forming violet coloured ppt of cuprous iodide and iodine.

7. Action with potassium ferrocyanide solution

Copper sulphate soln with potassium ferrocyanide soln gives chocolate brown ppt of copper ferrocyanide.

Zinc [30Zn]

Transition elements are those elements which have partially filled d-orbitals either in atomic form or their important compounds.

Zinc is non-typical transition elements. Zinc has 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ electronic configuration which is completely filled d-orbitals in all state but to be non transition elements they show d-block incomplete filled d-orbitals. Therefore, zinc is non-typical transition elements.

Main ores of zinc

• Zinc blende = ZnS
• Calamine or zinc spar = ZnCO₃
• Zincite or red zinc = ZnO
• Franklinite = ZnO·Fe₂O₃
• Willemite = ZnO·SiO₂

Extraction of Zinc

Specially zinc is extracted from its zinc blende or calamine going through following process.

1. Concentration

The big lumps of ZnS is first crushed and grinded into fine powder then concentrated by froth flotation process.

2. Roasting

Concentrated sulphide ore are then subjected for roasting at about 600°C in excess of air.

If carbonated ore are used then calcination process is applied in place of roasting.

In this process moisture as well as volatile impurities are removed.

3. Reduction [Smelting]

Roasted or calcined ore are mixed with coke then placed in vertical retort furnace and then heated externally by producer gas. The zinc oxide is reduced into free mercury vapour. Thus obtained zinc then vaporized and passed to the condenser to get molten zinc which is called zinc spelter.

4) Purification

Thus obtained spelter zinc is purified by electrolysis in which impure zinc is made anode and thin sheet of pure zinc is made cathode and ZnSO₄ soln is used as electrolyte. When electricity is passed then pure zinc is deposited on cathode.

Properties of Zinc

It is bluish white shining metal.

1) Action with air

Pure zinc is not affected by dry air while in moist air it tarnished and become dull due to formation of basic zinc carbonate [ZnCO₃·Zn(OH)₂].

Zinc when heated in air, it oxidized into phosphorescent wool [ZnO].

2) Action with water

Pure zinc does not react with water but impure zinc decomposes on boiling and produce hydrogen gas.

3) Action with acids

Zinc metal produce hydrogen gas with both conc and dil. HCl.

Zinc metal produce hydrogen gas with dil H₂SO₄ and SO₂ gas with conc H₂SO₄.

Nitric acid produces different oxides of nitrogen with zinc metal.

4) Action with alkali

On boiling with caustic soda zinc evolves hydrogen gas.

5) Displacement reaction

Zinc can displace copper, mercury from their salt soln.

Uses

• It is used for galvanizing iron.
• It is used for laboratory preparation of hydrogen gas.
• It is used as electrode in electrochemical cell.
• It is used to make alloys like brass.

Galvanization

Galvanization is the process in which a thin layers of zinc is coated or deposited over the iron sheets or others to protects them from rusting.

Compounds of Zinc

A. Zinc oxide [ZnO] or philosopher’s wool or zinc white

Preparation

1. By heating metallic zinc in air

2. By heating carbonates, hydroxides, nitrate, sulphates of zinc

Properties

1) Action with reducing agents

Carbon and hydrogen reduce zinc oxide into metallic zinc.

2) Amphoteric nature

ZnO combines both acid and base then form salt and water.

3) Action with cobalt nitrate

When ZnO is heated with cobalt nitrate then double oxide of cobalt zincate is formed called Rinman’s green [CoZnO₂].

Uses of ZnO

• It is used as white paint by the name zinc white or Chinese white.
• It is used to prepare green pigments called Rinman’s pigment.
• It is used in medicine (mild antiseptic) and teeth cementing.

B) Zinc sulphate [ZnSO₄·7H₂O] or white vitriol

Preparation

1. Zinc sulphate can be prepared by the action of dil H₂SO₄ on Zn, ZnO, Zn(OH)₂, ZnCO₃.

2. Zinc sulphate can be prepared by heating zinc blende with excess of air.

Thus obtained ZnSO₄ dissolved in water and then heated up to crystallization point to get crystals of ZnSO₄·7H₂O.

Mercury [80Hg]

Main ore

Cinnabar: HgS, Mercuric sulphide.

Extraction of Mercury

Mercury can be extracted from its cinnabar ore which includes following process.

1) Concentration

The ores are first crushed and grinded into fine powder then concentrated by froth flotation process.

2) Roasting

In this process concentrated ore are heated in excess of air then oxide of mercury is obtained.

3. Reduction

a) Smelting

In this process roasted ore are mixed with coke then heated in shaft furnace to about 400°C to be reduced into free mercury vapour. Thus obtained mercury is passed in cooling to get liquid mercury.

4) Purification

a) By Filtration

Thus obtained mercury is filtered through canvas or chamois leather and it separate impurities like bismuth, lead etc.

b) By treatment with dilute HNO₃

When mercury is treated with dil HNO₃, most of the metal present in Hg as impurities gets dissolve and removed.

c) By distillation in vacuum

When dry mercury is distilled in vacuum then highly pure form of mercury is obtained.

Properties

Mercury is silvery white and heaviest liquid at ordinary temperature.

Properties of Mercury

1) Action with air

When mercury is heated at 350°C then it is oxidised to mercuric oxide.

2) Action with H₂SO₄

Only hot and conc H₂SO₄ react with mercury and gives SO₂ gas.

3) With sulphur

4) Action with HNO₃

Mercury gives nitric oxide with dil HNO₃.

Conc HNO₃ gives NO₂ with mercury.

5) Action with halogen

On heating mercury gives dihalide with halogen.

6) Action with aqua-regia

The mixture of conc HNO₃ and conc HCl in 1:3 ratio by volume is called aqua regia. When it reacts with mercury then mercuric chloride is obtained.

7) Action with metals

Mercury reacts with metals and gives amalgam.

8) Tarnishing of mercury

Mercury when becomes contact with ozone then mercurous oxide is formed which is dissolved in Hg leaving dark grey colored or special markings is called tailing of mercury.

Uses

• It is used in mercury vapour lamp.
• It is used in thermometer.
• It is used for making amalgam.
• It is used as reducing agent.

Compounds of Mercury

A) Mercurous chloride Hg₂Cl₂ or HgCl [calomel]

Preparation

1) By heating mercuric chloride with mercury

2. By heating mercuric sulphate, sodium chloride and mercury

3. By reducing mercuric chloride with stannous chloride

4. By adding soluble chloride in soluble mercurous nitrate soln

Properties [Mpt 302°C + bpt 324°C]

It is white amorphous solid, insoluble in water and almost all acids.

1) Action with aqua-regia

2) Action with ammonia

Calomel with NH₃ ammonia and gives mercurous amido chloride.

3. Action with SnCl₂

Mercurous chloride gives metallic mercury with stannous chloride.

4. Action with conc. HCl

It dissolved in conc HCl in presence of strong oxidizing agent.

Uses

• It is used in medicine as purgative [blue bottle].
• It is used as calomel electrode.
• It is used as fungicides.

IRON [Fe]

Electronic configuration: [Ar] 4s² 3d⁶

Main ores of Iron

• Haematite = Fe₂O₃
• Limonite = Fe₂O₃·3H₂O
• Magnetite = Fe₃O₄
• Iron pyrite = FeS₂
• Copper iron pyrite = CuFeS₂
• Siderite = FeCO₃

Extraction of Iron

Specially iron is extracted from its haematite or iron pyrite ore. It includes following steps.

1. Crushing and pulverization

Concentrated haematite ore is first crushed then pulverized to form fine powder and concentrated by gravity separation process.

3. Calcination

Concentrated ore are calcined in limited or absence of air. In this process impurities are removed and their volatile oxide. Ferrous oxide and carbonate also changes into ferric oxide.

4. Reduction

Reduction process is carried out by smelting [carbon-reduction process]. Smelting is carried out in blast furnace which contains mixture of calcined ore, coke and limestone.

a. Zone of combustion

In the zone of combustion, coke burns with air and form CO₂ gas.

b) Zone of fusion

In the zone of fusion, upcoming CO₂ gas is fused with coke and CO is formed. If the ferric oxide is present then reduced into free iron.

c) Zone of slag formation

In this zone, flux is fused with oxide of impurities and form slag.

d) Zone of reduction

In this zone CO gas coming from zone of fusion is reduced the oxide of iron into free iron of metallic iron.

Thus obtained free metallic falls down and melts at the bottom of furnace. The free metallic silicon, the obtained iron contains impurity like C, P, Si, Mn and S etc. Therefore it is called cast or pig iron.

Properties of Iron

1) Action with H₂SO₄

Iron gives H₂ gas with dil H₂SO₄ and SO₂ gas with conc H₂SO₄ in presence of heat.

2) Action with HNO₃

• Very dilute nitric acid gives ammonium nitrate with iron.
• Dilute nitric acid gives nitrous oxide with iron.
• Moderate (1:1) nitric acid gives NO and NO₂ gas with iron.

3) Action with HCl

Both dilute and conc HCl gives H₂ gas with iron.

4) Action with halogens

Iron gives ferric halide with halogens.

5. Action with air

When iron is exposed to air it forms rust.

Commercial varieties of Iron

There are three commercial varieties of iron.

1. Wrought iron

It is the purest form of iron contains about 0.25% of carbon and trace of S, P, Si, Mn etc as impurities. It is soft and malleable having melting point 1500°C.

2. Steel

It is intermediate form of iron contains about 0.25% – 2% of carbon and traces of S, P, Si, Mn etc as impurities. Its melting point is 1000 – 1400°C.

3. Cast or pig iron

It is the least pure form of iron contains about 2% – 4.5% of carbon along with other impurities like P, S, Si, Mn etc. It is hard and brittle having melting point 1200°C.

Manufacture of Steel

Steel is the intermediate form of wrought iron and cast iron. It is manufactured either adding carbon to wrought iron or removing carbon and other present in cast or pig iron. It contains 0.25 – 2% of carbon and little amount of Mn. Steel is manufacture by following process.

A. By Bessemer’s process

In this process the molten iron is poured into a large egg-shaped Bessemer converter. It is made up of steel and internal lining is basic or acidic medium depending upon the nature of impurities present. A blast of hot air under pressure is passed through the molten cast iron then following rxn occurs.

After removing all impurities, wrought iron is obtained then required amount of carbon is added in the form of spiegel iron which is an alloy containing Fe, Mn and carbon to get steel.

B. By open-hearth process

In this process, a mixture of cast iron, scrap iron and haematite ore is charged in a open hearth furnace. The internal lining of furnace is acidic or basic medium depending upon the nature of impurities. Due to the hot air blast following reaction occurs.

By removing all oxide slag then wrought iron is obtained then spiegel iron is mixed to obtain steel.

Advantages of open-hearth process over Bessemer’s converter

[No explanatory points are written under this heading in the supplied source page.]

Heat treatment of Steel

1. Annealing
2. Quenching
3. Tempering

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Rusting of Iron

Rusting is an electrochemical phenomenon in which there is formation of very loose non-coherent brown coat of hydrated ferric oxide [Fe₂O₃·xH₂O] on the outer surface of iron when it is exposed to moist air.

Electrochemical theory of rusting

According to this theory when impure iron is exposed to moist air, a kind of small electrochemical cells are set up bet’n impurities of iron and iron itself which is in contact of moisture [water vapour containing CO₂]. Here iron act as anode, impurities as cathode, soln of CO₂ and water as electrolyte and dissolved O₂ gas as depolarizer. During rusting following rxn takes place.

The ferrous and hydroxyl ion combine to form ferrous hydroxide which undergo atmospheric oxidation to form ferric hydroxide.

Thus obtained ferric hydroxide dissociate to form hydrated ferric oxide which is brown powder mass known as rust.

Prevention of iron from rusting

• By making coat of oil, grease, paint on outer surface of iron.
• By electroplating on surface with Ni, Cr, Cu etc.
• By using anti-rust soln like phosphoric acid.
• By galvanizing of iron with Zn, Cr etc.

Iron Salts and Biological Importance

Q.No. Write the molecular formula of green-vitriol and mohr’s salt and also write its uses.

1. Green-vitriol / hepta-hydrated ferrous sulphate [FeSO₄·7H₂O]

• It is used as reducing agent.

2. Mohr’s salt [FeSO₄·(NH₄)₂SO₄·6H₂O]

• It is used as reducing agent.
• It is used in volumetric analysis for standardization of KMnO₄ solution.

Biological importance of iron

• It acts as O₂ carrier in the blood.
• It acts in O₂ storage in muscle tissues.
• It acts in storing and scavenging of iron in animals.

Silver [Ag]

Main ores of silver

• Argentite Ag₂S
• Horn silver AgCl
• Lunar caustic AgNO₃

Extraction of Silver by cyanide process

Specially silver is extracted from its argentite ore. It includes following steps.

1) Concentration

Argentite is first crushed then pulverized to form fine powder and concentrated by froth flotation process.

2. Cyanide treatment

The concentrated ore is mixed with sodium cyanide soln giving a current of air then the solution of sodium argento cyanide is formed.

Since the rxn is reversible.

If the ore is horn silver:

3. Precipitation of silver

The soln obtained above is filtered and the filtrate is treated with zinc, where Ag is ppt.

The silver is separated by filtration and fused with borax or K₂CO₃ to get a compact mass of silver known as spongy silver.

4) Purification

Thus obtained silver is purified by electrolytic refining. Impure silver is made anode and pure silver is made cathode and AgNO₃ as electrolyte.

On electrolysis Ag deposited from the anode and get collected in the cathode.

At anode:

At cathode:

Uses

• To prepare coins and ornaments.
• In photography and electrical purpose.
• To prepare electrode and alloy.

Compounds of Silver

A. Lunar caustic or Silver nitrate [AgNO₃] preparation

1. By the action of nitric acid on silver

Properties

It is a white crystalline solid and soluble in water and alcohol.

1) Action with heat

2) Decomposition by organic matter

If AgNO₃ comes in contact with the skin in presence of sunlight, a permanent black stain is formed on the skin. This property has been used in the preparation of indelible ink that can’t be removed, ink which is used during election for marking the voter who have put the vote.

4) Action with NH₄OH

5) Action with KCN

6. Displacement rxn

7. Action with halides / Sulphate / Sulphide

Uses

• To silvering of mirror.
• In photography.
• To prepare indelible ink.
• To prepare Tollens’ reagent.

B) Horn silver or silver chloride (AgCl) preparation

By action of sodium chloride and silver nitrate

Properties

It is white solid.

1) Action with ammonia

2) Action with KCN

3) Action with sod. thiosulphate or hypo

Uses

• In photography.

Frosted Silver

The ornaments and articles of silver usually contains 6-7% copper to give a pure white appearance to the articles. These are heated in the air so that the copper near the surface is oxidized while silver remains as such. The oxide formed on the surface is left on the surface. This process is called frosting of silver and silver obtained is called frosted silver.

Purity of Gold

Pure gold is very soft and can’t be used for making jewellery, so it is generally alloyed with silver or copper to make it harder and modify its color. The purity of gold in jewellery is expressed in carat. It implies that no of parts by wt of gold in 24 parts by wt alloy. Pure gold is 24 carat. 18 carat gold means it contains 18 parts by wt of pure gold in 24 parts by wt of the alloy. Most of the jewellery is made up of 22 carat gold.