ores and minerals
DESCRIPTION
Topic on Exploring Material SCE 3103TRANSCRIPT
ORES AND MINERALSORES AND MINERALS
Very reactive metalsVery reactive metals can only be extracted from their can only be extracted from their ores by electrolysis such as K, Na, Ca, Mg, and Al.ores by electrolysis such as K, Na, Ca, Mg, and Al.
Discussion on the extraction of the following:Discussion on the extraction of the following:
i. Aluminium from molten aluminium oxide (Bauxite) i. Aluminium from molten aluminium oxide (Bauxite)
ii. Sodium from molten sodium chloride (Halite).ii. Sodium from molten sodium chloride (Halite).
iii. Iron from iron (III) oxide Feiii. Iron from iron (III) oxide Fe22OO33, (Hematite)., (Hematite).
iv. Lead from Lead (II) sulphid , PbS (Galena).iv. Lead from Lead (II) sulphid , PbS (Galena).
v. Tin@Stanum from Tin (IV) Oxide SnOv. Tin@Stanum from Tin (IV) Oxide SnO22 (Cassiterite). (Cassiterite).
K
Na Very reactive metals
Ca Their ores require strong reduction which is
Mg done through electrolysis of molten ores
Al
Carbon
Zn Fairly reactive metals
Fe Their ores can be reduced by heating
Sn strongly with carbon
Pb
Hydrogen
Cu Their ores can easily be reduced by heating
Hg directly in air
Ag Less reactive metal
Au They exist as free metals in nature
EXTRACTION OF TIN/STANUMEXTRACTION OF TIN/STANUM
The main ore of tin is cassiterite which contains tin The main ore of tin is cassiterite which contains tin (IV) oxide, SnO(IV) oxide, SnO22. .
First First - Ore is first crushed, grounded and washed.- Ore is first crushed, grounded and washed.
SecondSecond - Flotation - mixing it with oil and water. In - Flotation - mixing it with oil and water. In this flotation method, the tin minerals, which are this flotation method, the tin minerals, which are less dense, are trapped in the floating form. The less dense, are trapped in the floating form. The impurities such as soil and sand which are denser, impurities such as soil and sand which are denser, sink to the bottom.sink to the bottom.
ThirdThird - Roasted in the air. This converts the - Roasted in the air. This converts the sulphide of tin to oxide. At the same time, sulphide of tin to oxide. At the same time, impurities such as sulphur and oil are burnt off.impurities such as sulphur and oil are burnt off.
FourthFourth - Reduction of tin (IV) oxide to tin by carbon - Reduction of tin (IV) oxide to tin by carbon monoxide and coke.monoxide and coke.
SnOSnO22 + 2CO → Sn + 2CO + 2CO → Sn + 2CO22
SnOSnO22 + 2C → Sn + 2CO + 2C → Sn + 2CO SnOSnO22 + C → Sn + CO + C → Sn + CO22
Last Last -The molten tin is drained off into moulds to -The molten tin is drained off into moulds to become blocks.become blocks.
RoastedRoasted( Reduction)Heated with
coke and limestone in blast furnace
( Reduction)Heated with
coke and limestone in blast furnace
Molten tin is drawn off and moulded
Molten tin is drawn off and moulded
Tin block
Cassiterite Crushed and washed
Crushed and washed
Flotation to concentrate the
ore
Flotation to concentrate the
ore
Flow-chart below summarises the extraction of tin / stanum
Properties of Stanum, SnProperties of Stanum, Sn
– Melting point 232Melting point 232ooCC– Boiling point 2603Boiling point 2603ooCC– Silvery in colourSilvery in colour– Highly ductile and malleable at Highly ductile and malleable at
temperature 100temperature 100ooCC
Uses of Stanum, Sn in daily lifeUses of Stanum, Sn in daily life
Widely used in alloy making:Widely used in alloy making:
i.i. Produce bronze as alloy (70% Cu + 30% Sn).Produce bronze as alloy (70% Cu + 30% Sn). ii.ii. Industrial processes as in the form of:Industrial processes as in the form of:
Tinplate, pewter (96% Sn + 3 % Cu and 1% Sb) and Tinplate, pewter (96% Sn + 3 % Cu and 1% Sb) and solders (70% Pb + 30% Sn)solders (70% Pb + 30% Sn)
iii. iii. In aerospace industry ( Stanum +Titanium ).In aerospace industry ( Stanum +Titanium ).
iv. iv. Insecticides.Insecticides.
EXTRACTION OF ALUMINIUM
Aluminium is extracted from its ore (bauxite) which Aluminium is extracted from its ore (bauxite) which contains aluminium oxide Alcontains aluminium oxide Al22OO33 . 2H . 2H22OONote:Aluminium not from AlClNote:Aluminium not from AlCl33 because AlCl because AlCl33 does not melt when heated. does not melt when heated.
Aluminium oxide is mixed with cryolite, NaAluminium oxide is mixed with cryolite, Na33AlFAlF66
to lower the melting point of aluminium oxide from to lower the melting point of aluminium oxide from 20452045ooC to about 900C to about 900ooCC. .
4000 A current is used to keep the temperature of 4000 A current is used to keep the temperature of the electrolysis cell at 900the electrolysis cell at 900ooC.C.
Block of carbon act as anodesBlock of carbon act as anodesCarbon lining act as cathode.Carbon lining act as cathode.
Cathode: AlAl3+3+ + 3e → Al + 3e → AlAnode:
2O2O2-2- → O → O22 + 4e + 4e--
The overall chemical reaction is:The overall chemical reaction is: 2Al2Al22OO33 → 4Al + 3O → 4Al + 3O22
The oxygen liberated at the anode will react The oxygen liberated at the anode will react with the carbon electrode to produce carbon with the carbon electrode to produce carbon dioxide gas.dioxide gas.The anode is corroded slowly and must be The anode is corroded slowly and must be replaced form time to time.replaced form time to time.
Physical Properties of AluminiumPhysical Properties of Aluminium
1) Is strong.1) Is strong.2) 2) malleable . .3) Low 3) Low density..4) Resistant to 4) Resistant to corrosion because the presence because the presence
of an impervious oxide layer on the surface ofof an impervious oxide layer on the surface of aluminium.aluminium.
5) G5) Good conductor of heat and electricity. of heat and electricity.6) Can be polished to give a highly reflective6) Can be polished to give a highly reflective
surface.surface.
Chemical properties of aluminiumChemical properties of aluminium
1) Reaction with non-metallic elements when 1) Reaction with non-metallic elements when heated.heated.
4Al + 3O4Al + 3O22 2Al2Al22OO33
2Al + 3S 2Al + 3S AlAl22SS33
2Al + N2Al + N22 2AlN2AlN
4Al + 3C 4Al + 3C AlAl44CC33
2Al + 3Cl2Al + 3Cl22 AlAl22ClCl66
Chemical properties of AluminiumChemical properties of Aluminium
2) React with hydrochloric acid and 2) React with hydrochloric acid and sulphuric acidsulphuric acid
2Al + 6HCl → 2AlCl2Al + 6HCl → 2AlCl33 + 3H + 3H22
However, with hot dilute or concentrated sulphuric However, with hot dilute or concentrated sulphuric (VI) acid, sulphur dioxide gas is liberated(VI) acid, sulphur dioxide gas is liberated
2Al + 6H2Al + 6H22SOSO44 → Al → Al22(SO(SO44))33 + 3SO + 3SO22 + 6H + 6H22OO
Chemical properties of aluminiumChemical properties of aluminium
3) Reaction with alkalis3) Reaction with alkalis
The reaction is highly exothermic.The reaction is highly exothermic.
2Al + 2NaOH + 6H2Al + 2NaOH + 6H22O → 2NaAl(OH) + 3HO → 2NaAl(OH) + 3H22
Uses of AluminiumUses of Aluminium
Shiny metal – Used as jewelley.Shiny metal – Used as jewelley.
Low density - Used to make aeroplanes and Low density - Used to make aeroplanes and trains.trains.
Non- toxic –Used in a drink cans and roofing Non- toxic –Used in a drink cans and roofing materials materials
EXTRACTION OF IRON
Ores:hematite, Fe2O3 and magnetite,
Fe3O4.
First - remove the impurities.First - remove the impurities.
Then, concentrated ores are reduced by carbon in Then, concentrated ores are reduced by carbon in the form of the form of cokecoke in a very large and hot furnace in a very large and hot furnace called called blast furnaceblast furnace. Its temperature can reach up . Its temperature can reach up 20002000ooC.C.
A A small charge small charge ( consists of concentrated iron ( consists of concentrated iron ores, coke and limestone )is introduced ores, coke and limestone )is introduced from the from the top of the blast furnace top of the blast furnace at intervals of 10 to 15 at intervals of 10 to 15 minutes.minutes.
Blast of extremely hot air are pumped through the furnace via the bottom. The oxygen in the hot air reacts with coke to form
carbon dioxide . C + O2 → CO2
Blast of extremely hot air are pumped through the furnace via the bottom. The oxygen in the hot air reacts with coke to form
carbon dioxide . C + O2 → CO2
Excess carbon reacts with carbon dioxide producing carbon monoxide ( the main reducing agent) in the furnace.
C + CO2 → 2CO
Excess carbon reacts with carbon dioxide producing carbon monoxide ( the main reducing agent) in the furnace.
C + CO2 → 2CO
Carbon monoxide and carbon reduce the iron oxides to iron.
Fe2O3 + 3CO → 2Fe + 3CO2
2Fe2O3 + 3C → 4 Fe + 3CO2
Fe3O4 + 4CO → 3Fe + 4CO2
Fe3O4 + 2C → 3Fe + 2CO2
Carbon monoxide and carbon reduce the iron oxides to iron.
Fe2O3 + 3CO → 2Fe + 3CO2
2Fe2O3 + 3C → 4 Fe + 3CO2
Fe3O4 + 4CO → 3Fe + 4CO2
Fe3O4 + 2C → 3Fe + 2CO2
The following flow chart outlines the reduction of the iron ores The following flow chart outlines the reduction of the iron ores
The molten iron is collected at the bottom of the The molten iron is collected at the bottom of the furnace. It is drained off periodically into moulds furnace. It is drained off periodically into moulds and is allowed to cool. The product known as cast and is allowed to cool. The product known as cast iron.iron.
At the same time, the At the same time, the limestone decomposes tolimestone decomposes to..
CaCOCaCO33 → CaO + CO → CaO + CO22
The The calcium oxide then reacts with the impurities calcium oxide then reacts with the impurities in the oresin the ores, which consist mostly of sand, SiO, which consist mostly of sand, SiO22 to to form calcium silicate, CaSiOform calcium silicate, CaSiO33 or or slagslag..
CaO + SiOCaO + SiO22 → CaSiO → CaSiO33(l)- slag(l)- slag
Properties and Uses of IronProperties and Uses of Iron
Cast iron is very brittle (it cracks easily) Cast iron is very brittle (it cracks easily) butbut it has a it has a greater resistance to corrosion than either pure iron greater resistance to corrosion than either pure iron or or steel..
Cast iron is used for manhole covers on roads and Cast iron is used for manhole covers on roads and pavements and as engine blocks for pavements and as engine blocks for petrol and diesel and diesel engines.engines.
Pure iron is called wrought iron. Wrought iron is Pure iron is called wrought iron. Wrought iron is malleable and is mainly used in ornamental work for malleable and is mainly used in ornamental work for gates.gates.
React as catalyst in the Haber Process.React as catalyst in the Haber Process.
EXTRACTION OF LEAD, Pb
Lead Ores - Galena, PbS.Lead Ores - Galena, PbS.
Process: (heating & electrolysis)Process: (heating & electrolysis)
FirstFirst - Lead bromide must be heated until - Lead bromide must be heated until it is molten before it will conduct electricity.it is molten before it will conduct electricity.
SecondSecond - Electrolysis separates the - Electrolysis separates the molten ionic compound into its elements molten ionic compound into its elements
Cathode:Cathode: PbPb2+2+ + 2e- → Pb + 2e- → Pb
Anode:Anode:
2Br2Br-- → Br → Br2 2 + 2e+ 2e
The overall reaction isThe overall reaction is
PbBrPbBr22(l) → Pb(s) + Br(l) → Pb(s) + Br22(g)(g)
Properties of Lead, PbProperties of Lead, Pb
– Melting point 327.4Melting point 327.4ooCC– boiling point 1750boiling point 1750ooCC– Soft metal.Soft metal.– Easily Easily malleabilitymalleability or can be shaped. or can be shaped.– Grey in colour.Grey in colour.– Resistance to corrosion.Resistance to corrosion.
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