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LECTURE NOTES
METALS
Definition:
A metal is an element which ionises by the loss of its valence electrons.
M -----------→ Mz+ + zeWere z is the number of valence electrons.
The number of electrons given out by a metal characterises that metal and gives it an oxidation number or
oxidation state. For example, Potassium and other group Ia metals ionize as follows:
K
---------→ K+ + eNa --------→ Na+ + e(Oxidation state = +1)
Aluminium loses three electrons as follows:
Al ---------→ Al3+ + 3e(Oxidation state = +3)
Groups Ia, IIa and IIIa have one oxidation state each.
Transition metals however, have variable oxidation states. The variable oxidation states of transition metals
shall be explained later.
Metals generally form cations when they ionize or when their compounds are in solution.
NaCl ---------→ Na+ (aq) + Cl+ (aq)
CuSO4 --------→ Cu2+ (aq) + SO42- (aq)
Position of Metals in the Periodic Table
Metals are generally found on the left side of the diagonal division (line) which runs from Boron to Polonium in
the periodic table. This zig-zag line divides the elements into metals, non metals and metalloids. Elements on
the left are metals while those on the right are non metals. Those found along the line (e.g. Silicon, Germanium)
are metalloids. Metallic character increases from top to bottom down a group while it decreases from left to
right across a period. Non-metallic character on the other hand, decreases from top to bottom and increases
from left to right across a period in the periodic table.
Group Ia contains metals called alkali metals (K, Li, Na, Rb, Cs, Fr)
Group IIa metals are called alkaline – earth metals (Be, Mg, Ca, Sr, Ba)
Group IIIa metals include Aluminium.
Other metals found in the periodic table include the transition metals. These are found between Group IIa and
IIIa. The first series include Sc, Ti, V, Cr, Mn, Fe, Mn, Cu etc.
Amongst the transition elements are the lanthanide and actinide series. All these are metals.
Physical Properties of Metals
The physical properties of metals can easily be explained in terms of the electron cloud model of metallic
bonding. The physical properties of the different metals make them useful for different purposes. The following
are among the physical properties of metals.
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
a. Almost all metals are solids except mercury and caesium. Gallium melts in a protected band.
b. Metals have high boiling points and melting points. These increase across a period
c. They have relatively high densities which increase down a group and from left to right.
The properties above are due to the strong electrostatic force of attraction between electron could and
metallic ions (metallic bond) and the tightly packed crystal lattice of the metallic structure.
d. They are malleable (can be pounded/hammered into thin sheets)
e. They are ductile (can be drawn into wires). The atoms are arranged in order and are in the same size.
This makes it easy for layers of atoms to slide over each other when a force is applied making them
malleable, ductile, and soft in some cases.
f. They are hard with varying degrees of hardness.
g. Metals conduct heat. (e.g. Aluminium is used for saucepans).
h. They conduct electricity. The mobile electrons (electron cloud) make the transfer of heat and electrical
energy possible. Copper is used in electric cables.
i. Most metals (except group Ia, and IIa) have great tensile strength. Such metals are used for making
bridges, buildings and manufacturing cars. Steel is useful for these purposes.
j. They are sonorous, producing sound when hit
k. They are opaque, shiny and lustrous e.g. gold because visible light waves are not readily transmitted
through the bulk of their microstructure.
Chemical Properties
The groups Ia and IIa are the most active metals. Most metals have positive valencies, losing electrons as they
have low combining power which makes them easily lose electrons.
The reaction of metals is characterized by electron loss amongst which are:
a. Reaction with air/oxygen (oxidation)
Metals generally react with oxygen to form oxides over changing timescales.
The reaction is faster (few seconds) and rapid with group Ia, followed by group IIa. It is however, very
slow in others, taking years in some cases ( e.g Fe rusts, Cu, Zn and Ni). Palladium, platinum and gold
do not react at all.
4Na + O2 ------→ 2Na2O
4A1 + 3O2 -------→ 2Al2O3
The oxides of metals are mostly basic with a few being amphoteric unlike the non-metallic oxides that
are acidic and neutral. CaO, Na2O, K2O, MgO are basic. They react with water to form alkalis and react
with acids to form salts and water.
Na2O + H2O ------→ 2NaOH(aq)
CaO + H2SO4 -----→ CaSO4 + H2O
Al2O3, ZnO, BeO, Ga2O3 are amphoteric oxides.
b. Reaction of metals with water/steam
Metals react variedly with water/steam to form the metal hydroxide and hydrogen gas. Potassium
explodes with cold water. Sodium reacts violently, calcium reactions quickly with cold water.
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
Magnesium reacts slowly but violently with steam to form magnesium oxide and hydrogen. Fe also
reacts with steam but slowly, Pb, Cu and Ag do not react with steam or water.
2Na + 2H2O(l) -----→ 2NaOH(aq) + H2
3Fe + 4H2O(g) -----→ Fe3O4(s) + 4H2
c. Reaction of metals with dilute acids (HCl in particular). Many metals react to form salts and hydrogen
gas. K and Na react explosively. Ca and Mg do so violently and rapidly respectively. Zn reacts
moderately.
Zn + 2HCl -----→ ZnCl2 + H2 (quickly)
d. Reactions with other non-metals such as sulphur, nitrogen, chlorine occur at high temperatures. The
corresponding compounds are formed
Mg + S ------→ MgS
e. Reduction of metallic oxides. This is possible using carbon or hydrogen
CuO + H2 -------→ Cu + H2O
Fe2O3 + 3C ------→ 2Fe + 3CO2
Oxides of potassium, sodium, calcium and magnesium cannot be reduced.
f. Displacement reactions: More active metals displace the less active metals from their compounds.
Examples are:
Zn + CuO → ZnO + Cu
Mg + PbSO4 → MgSO4 + Pb
g. Action of heat on metal trioxocarbonates (IV) with the exception of the trioxocarbonates (IV) of K and
Na, the rest decompose on heating. Those of the moderately active metals (including Mg and Ca),
decompose into the oxides and carbon (IV) oxide. Those of the least active metals decompose into the
metal oxygen and carbon (IV) oxide. Eg.
CaCO3 ------ht---→
CaO + CO2
ht
PbCO3
----- ---→
PbO + CO2
2Ag2CO3 ------→
4Ag + 2CO2 + O2
Uses of Metals
....check the various groups.
GROUP IA METALS (The Alkali Metals)
Members include Lithium Li., Sodium Na, Potassium K, Rubidium Rb, Caesium Cs and Francium Fr. They are
not found free in nature due to their high reactivity. They are so easily oxidised. Francium and Caesium are
short-lived and radioactive isotopes but the others are common on earth’s crust.
Each consists of one electron in their outer shells, and ionises by loss of one electron
M -----→ M+ + eWith the exception of lithium, the metals are soft, silvery and corrosive. They have reactively low melting and
boiling points than their group IIa counterparts
Chemical Properties
1. They react with limited/excess air to form oxides. Oxides formed are either basic, peroxides or
superoxides (K2O, NaO2, or K2O2)
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
2. They react with water or moisture in the air to form hydroxides.
2K + H2O -----→ 2KOH.
Because of the ease with which alkali metals react with air and water, they are stored under paraffin
oil/mineral oil.
3. Reaction with other elements (non-metals) such as Cl2, N2 lead to formation of chlorides (NaCl,
KCl) and nitrides such as Li3N
Uses of Group One Metals
 Lithium compouds are used for treating some mental disorders (manic depression) lithium is used as
heat transfer medium in exceptional. Nuclear reactors.
 Sodium salt (NaCl) is essential for life. The metal is used as reducing agent in the manufacturing of
drugs and dyes
 Sodium compounds (CO32-, HCO3-) are used for baking and other household purposes)
 Some K – salts are essential for life. KNO3 is used as fertilizer
GROUP IIA (Alkaline – Earth Metals)
Members are Beryllium Be, Magnesium Mg, Calcium Ca, Strontium Sr, Barium Ba and Radium, Ra. They are
characterised by possession of two valence electrons. Other characteristics include:
a. They ionise by loss of the 2 electrons, hence they are divalent and good reducing agents.
M -----→ M2+ + 2eb. They are silvery white, malleable and ductile, harder than group Ia
c. Their reactivity increases from top to bottom
d. They are not as reactive as group Ia but reactive enough not to be found in the free states.
Chemical Reactions
The reactions of group IIa are wider but less reactive than those of group Ia.
e. With oxygen, oxides (e.g CaO, MgO) and super oxides (e.g BaO2) are formed,
f. With hydrogen, halogens, nitrogen and sulphur, hydrides (e.g MgH2), nitrides (e.g Ca3N2), halides
(CaCl2, MgCl2) and sulphides (e.g MgS) are formed.
g. With water, calcium, strontium and barium react at 250c to form the respective hydroxides. Magnesium
reacts at higher temperatures to form the oxide while beryllium does not react with water or steam.
Ca + 2H2O ------→
Ca (OH)2 + H2
Mg + H2O-----→ MgO + H2
NOTE: Group IIa compounds are less soluble in water than compound of group Ia
Uses of Group IIa Metals
*Windows for x-ray tubes are constructed using beryllium
*Mg is used in photographic flash accessories and fireworks.
*Mg is also used in many alloys for manufacturing building materials
*Ca is used as reducing agent in the extraction of uranium and thorium. It is a component of many alloys
*Sr salts are used in fireworks and flares
*Ba is a constituent of alloys
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
GROUP IIIA
Members are Boron B, Aluminium Al, Gallium Ga, Indium In , and Tellurium Te. Of these, the common
member is Aluminium. The properties of the elements vary less regularly down the group than those of groups
Ia and IIa.
Members are all solids with the exception of boron which is a non metal. With the exception of B (which
crystallises as a covalent solid and has a high melting point 23000c), others have considerably lower melting
points.
Al is the most active member and most abundant metal in earth’s crust and 3rd most abundant element. It is soft,
malleable and ductile. It has a low density hence its being used as a light weight structural metal, usually
alloyed with Mg and Cu, Si to increase its strength. It also conducts electricity and so is used in electrical
transmission lines and wiring of homes.
Chemical Reactions
a. Al is a strong reducing agent
Al ------→ Al3+ + 3e
b. It is quite reactive, but a thin, hard and transparent film of Al2O3 forms on the surface when it comes in
contact with air. This protects the Al from further oxidation. Thus Al is passive towards HNO3.
However, when the oxide layer is removed, it can react with HNO3
Al + 4HNO3 -----→ Al(NO3)3 + NO + 2H2O
d- TRANSITION ELEMENTS (METALS)
These are elements that contain partially or completely filled d-orbitals (or sub-shells) in at least one of their
compounds. Transition elements denote those elements that are in the middle of the periodic table which
provides transition between base formers on the left and acid formers on the right. They are found between
groups IIa and IIIa, between s- and p-block elements. They are often referred to as the d-block elements and
members of the first transition series include:
Scandium, Sc
= 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d1
Note that the configuration 1s2, 2s2, 2p6, 3s2, 3p6, 4s2 is same with that of Ca.
Titanium, Ti
= [Ca] 3d2
Vanadium, V
= [Ca] 3d3
Chromium, Cr
= [Ca] 3d4. It can also be 1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5
Manganese, Mn
= [Ca] 3d5
Ferrum (Iron), Fe
= [Ca] 3d6
Cobalt, Co
= [Ca] 3d7
Nickel, Ni
= [Ca] 3d8
Cuprum (Copper), Cu
= [Ca] 3d9 or 1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d10
Zinc, Zn
= [Ca] 3d10
Characteristics of Transition Metals
a. All of them are metals
b. Transition metals are characterised by the possession of variable oxidation states. Vanadium for
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
c.
d.
e.
f.
g.
instance, has oxidation numbers (state) of +3, +4, +5. Manganese exhibits +2, +4, +6, +7 oxidation
states amongst others. The 3d and 4s orbitals have very close energy levels. Therefore d-block elements
can place their electrons in either the 3d or 4s orbitals for bond formation. As the variation in successive
ionisation energies is not great, d-block elements can form cations of different charges with similar
stability. Therefore various oxidation states can be attained.
Most of them are hard and more brittle than groups Ia, IIa and IIIa metals. The hardness is due to the
stronger metallic bond.
They have higher melting and boiling points than non-transition metals/elements.
Many of the metals and their compounds are effective catalysts. Examples include Iron or iron (III)
oxide, Fe2O3 is used in the Haber process for the manufacture of ammonia and vanadium (v) oxide,
V2O5 used in the contact process for the manufacture of tetraoxosulphate (VI) acid, H2SO4.
Many of the transition metals and their compounds are paramagnetic
They form coloured ions/compounds especially their hydrated forms. This is related to the incompletely
filled d-orbitals
METALLURGY
Metallurgy refers to the commercial extraction of metals from their ores and the preparation of such metals for
use. It includes several steps such as:
i. Mining the ore
ii. Pre-treatment of the ore (ore concentrations)
iii. Reduction of the ore to the free metal
iv. Refining or purification of the metal and
v. Alloying where necessary
Occurrence of Metals
Most metals generally occur in nature (in the earth crust) in combined states/forms called ores from which the
metals can be extracted. The ores contain minerals (pure compound of the metal) and other earthly materials
(impurities) called gangue. Gangue consists of sand, clay, rock, soil, etc. This is common for reactive metals.
The ores of such metals can be oxides, sulphides, trioxocarbonates (IV), chlorides or tetraoxosulphates (VI).
Less reactive metals occur free in nature. Examples of less reactive metals include gold, silver, platinum,
osmium, bismuth and rhodium. The properties of metals influence the kinds of ores in which they are found,
and the metallurgical processes used to extract them from their ores. Metals with negative standard reduction
potentials (less active metals) are found in nature in the combined state. Those with positive standard reduction
potentials (non-active metals) may occur in the uncombined state.
The following are examples of metallic ores:
Oxides = hematite Fe2O3, bauxite Al2O3, cassiterite SnO2, Silica SiO2
Sulphides = chalcopyrite CuFeS2, galena PbS, Sphalerite ZnS, iron pyrites, FeS2
Chlorides = rock salt NaCl, sylvite KCl, canarlite KCl.MgCl2-6H2O
Carbonates = limestone CaCO3, magnetite MgCO3, dolomite MgCO3.CaCO3
Sulphates = Gypsum CaSO4-24H2O, Epsom salt MgSO4.7H2O, Barite BaSO4
Silicates = Beryl Be3Al2Si6O18, Kaolinite Al2(Si2O8)(OH)4, Spodumene LiAl(SiO3)2.
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
Mining
This is carried out by Geologists and Mining Engineers. Details of how mining occurs shall not be discussed
here.
Pre treatment of Ores / Concentration of Ores.
After mining of ores, the ores must be concentrated by removal of most of the gangue/impurity. Various
methods of concentrating ores abound. Before concentration however, the ore must be pulverised, crushed into
tiny particles.
a. For sulphide ores, the gangue is lighter than the pure ore. After pulverization, the lighter gangue
particles are removed by a variety of methods such as the use of a cyclone separator. The cyclone
separator enriches metal ores. The crushed ore is blown in at high velocity. Centrifugal force takes the
heavier particles with the higher percentage of metal to the wall of the separator. These particles spiral
down to the collection bin at the bottom. Lighter particles not rich in the metal, move to the centre and
are carried out to the top in the air stream.
b. Another method is flotation process. In this process, a stream of air is blown through a swirled
suspension of an ore in water and oil. Bubbles form in the oil on the mineral particles and cause them to
rise to the surface. The bubbles are prevented from breaking and escaping by a layer of oil and
emulsifying agent. A frothy ore concentrate forms at the surface. The relatively light sulphide particles
are suspended in the water-oil detergent mixture and collected as froth. The denser material sinks to the
bottom of the container.
c. Roasting of ores: This is employed for some sulphide ores during which they are converted to oxides by
heating below their melting point in the presence of oxygen. 2ZnS(s) + 3O2(g) ---------→ 2SO2(g)
d. Washing with water: This enables the reduction of the gangue from the ore. It is a method commonly
employed for tin ores.
e. Another method involves chemical modification. This process converts the compound (ore) to a more
easily reduced form. It is used for trioxocarbonates (iv) and hydroxides to drive off CO 2 and H2O
respectively.
CaCO3(s) ---→ CaO(s) + CO2(g)
Mg (OH)2(S) ---→ MgO (s) + H2O(g)
Reduction to the Free Metal (Smelting)
A metal ore must usually, be smelted – heated with a reducing agent in order to extract the pure metal. There
are three methods of extraction:
i.
Roasting/Heating in air
ii.
Heating/Reduction with coke (carbon) or carbon(ii) oxide
iii.
Electrolysis
Roasting in air
This is employed for the ores of least reactive metals such as lead, copper, silver, mercury, platinum and gold.
These elements either occur in the free state or as sulphides
HgS + O2 → Hg(g) + SO2(g)
Cu2S + O2 → 2Cu(s) + SO2(g)
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
Reduction using Carbon (ii) Oxide or Coke
This method is employed for the moderately reactive metals such as iron, zinc, chromium and manganese. In
this case, the carbon (ii) oxide serves as a reducing agent. The ores are usually oxides. E.g.
a. 2ZnS + 3O2
----→ 2ZnO + 2SO2
ZnO + C
----→ Zn(s) + 2SO2
b. Fe2O3 + 3CO
----→ 2Fe(S) + 3CO2(g)
c. SnO2 + C
---→ Sn(s) + CO2(g)
Reduction using electricity (electrolysis)
Electrolysis is the chemical decomposition of a compound brought by the flow of a direct current through a
solution or molten compound. This process can be used to obtain free metals from their ores.
Examples of such metals are Potassium, sodium, calcium, aluminium, magnesium etc (the active metal).
For the extraction to be carried out, the molten compounds are used. During the process the metal ions are
reduced at the cathode to the free metals, examples:
Al3+ + 3e- → Al(s)
Na+
+ e- → Na(s)
Ca2+ + 2e- → Ca(s)
Electrolysis uses very large amount of energy/electricity which is expensive in terms of fuel costs due to the
high current needed to heat the ores (salts) to melting points. The process is much more expensive than
reductions using C or CO; thus aluminium which is the most common metal in the Earth’s crust, is expensive
where as iron is rather cheap.
In the extraction of calcium from molten CaC12, Some CaF2, must be added to lower or reduce the melting
point of CaC12 thereby reducing the amount of energy needed to melt the ore (and hence reduce the cost of
extraction).
EXTRACTION OF COPPER
Copper is extracted from chalcopyrite, CuFeS2 (CuS.FeS) mainly. Other ores of copper include azurite,
Cu3(CO3)2(OH)2 and malachite, Cu2CO3 (OH)2. CuFeS2 is actively a mixture of CuS and FeS.
After mining, the CuFeS2 is concentrated using Flotation process.
It is then roasted to remove impurities after which air is used to convert iron (ii) sulphide to iron (ii) oxide.
2CuFeS2 + 3O2 → 2FeO(s) + 2CuS(s) + 2SO2(s)
Sand, silicon (iv) oxide, SiO2 and crushed limestone, CaCO3, are added to the mixture in a reverberatory
furnace at 1100C to remove the FeO. During this process, CuS is reduced to Cu2S.
2CuS + O → Cu2S + SO2(g)
CaCO3 + SiO2 → CaSiO3(1) + CO2(g)
CaSiO3 + FeO + SiO2 → CaSiO3, FeSiO3(l)
The slag is drained off periodically leaving the Cu2S
The molten Cu2S is again heated and treated with air to oxidize the sulphate ions and reduce the copper (i) ions
into metallic copper.
Cu2S(l) + O2 → 2Cu(l) + SO2(g)
The impure copper is refined/purified using electrolysis
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
Copper from the blast furnace contain numerous impurities; it is purified by electrolysis. In the electrolytic cell
for the purification of the copper, the impure copper is used as the anode while a piece of pure copper rod is
used as the cathode. The electrolyte is a solution of copper II) salt, usually copper (ii) tetraoxosulphate (vi),
CuSO4 solution.
The copper anode is not an inert electrode – it does not remove electrons from an ion in solution, but loses
electrons itself.
At the anode
Neither the SO42- nor the OH- ions are oxidised at the anode. Instead, pure copper atoms from the impure copper
rod are oxidised to copper (II) ions (dissolved into solution) as;
Cu → Cu2+ + 2eThese ions move to the cathode along with the Cu2+ of the electrolyte and are reduced to the free metal, Cu.
Cu2+ + 2e- → Cu
As the pure atoms from the anode dissolve and migrate to the cathode, impurities fall to the bottom of the tank.
As the electrolysis continues, the anode decreases in size while the copper cathode increases in size due to the
deposit of copper formed at the cathode.
EXTRACTION OF ALUMINIUM
Pure aluminium oxide is extracted from bauxite, Al2O3, through electrolysis. Bauxite is a mixture of aluminium
oxide, iron oxide, silicon dioxide and variable amounts of water.
The aluminium oxide cannot be melted on an industrial scale since it is melting temperature is about 2045 0C. It
is therefore dissolved in molten cryolite, Na3A1F6, at about 9500C and electrolysed using the Hall – Heroult
process (cell).
The inner surface of the cell is coated with carbon (graphite) or carbonised iron which functions as the cathode
at which aluminium ions are reduced to the free metal. Blocks of graphite hang in the middle of the tank as the
anode.
Electricity is passed and electrolysis begins with the movement of ions to opposite poles. The ions present in the
molten compound (bauxite) are:
A13+ and O2The A13+ ions migrate to the cathode while the O2- ions migrate to the anode.
At the anode:
Oxide ions are oxidised to oxygen which immediately reacts with the graphite anode. As a result of the attack of
the anode by the oxygen, the anode needs to be replaced from time to time:
2O2- ------→ O2 + 4eC + O2 ------→ CO2
At the cathode:
Aluminium ions are reduced to molten aluminium at the cathode:
A13+ + 3e- ------→ A1
The molten aluminium formed is denser than the cryolite and so it collects at the bottom of the cell from where
it is siphoned out from time to time and cooled to a solid.
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
The large amount of electrical energy needed in this electrolysis makes the production of aluminium from its
ore very expensive. A more economical process, the Alcoa chlorine process, has been developed on a
commercial scale. The anhydrous bauxite is first converted to AlCl3 by reacting with chlorine in the presence of
carbon. The AlCl3 is then melted and electrolysed to give aluminium and the recovered chlorine is re-used in
the first step.
Al2O3 + 3C + 6Cl2 -----------→ 4AlCl3 + 3CO2
AlCl3 -----------→ 2Al(l) + 3Cl2
This process uses only 30% as much electrical energy as the Hall – Heroult process.
Nowadays, methods of recycling used aluminium use less than 10% of the energy required to make the new
metal from bauxite by the Hall – Heroult process.
Aluminium is:
 Soft and of low density – it needs to be alloyed to be useful for engineering applications
 Malleable and ductile
 A very good conductor of electricity
 Resistant to corrosion (see below)
It is used as an alloy (Duralumin) with magnesium and some copper for making aircraft (because of low
density; not light) and with magnesium for car bodies.
It is used with a steel core (for strength) for overhead power lines, and without the steel for underground cables.
It is used to make a wide variety of items for construction, e.g. window frames, because of its ease of extrusion
into complex shapes and its corrosion resistance.
EXTRACTION OF IRON
Iron is extracted either from haematite Fe2O3 or magnetite Fe3O4. Other raw materials include coke, limestone
and hot air. Recall that carbon and carbon monoxide can reduce the oxides of less reactive metals. A wide
variety of oxides of less reactive metals can be reduced by carbon or carbon monoxide:
Fe2O3 + 3C ----→ 2Fe + 3CO
Fe2O3 + 3CO ---→ 2Fe + 3CO2
The extraction of iron is the largest use of the process and it takes place in the blast furnace. The structure of the
blast furnace is essential for the process.
The top of the furnace is charged with a mixture of coke, the iron ore (Fe2O3 or Fe3O4) and limestone (CaCO3).
The coke serves to produce heat and the reducing agent, CO. The limestone is used to remove silica impurity
from the ore.
These reactions occur near the air inlet. A blast of hot air from the bottom burns the coke to produce CO with
the evolution of more heat.
C + O2 ---→ CO2 + heat; an exothermic reaction
CO2 + C ---→ 2CO, an endothermic reaction
The CO produced then reduces the iron ore. The reaction with CO is endothermic and uses about half the
energy in the furnace.
Fe2O3 + 3CO ---→ 2Fe + 3CO2
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
Fe2O3 + 3C ---→ 2Fe + 3CO
The main impurity in the ore is silica, SiO2. This is acidic and reacts with CaO (a base) to give molten slag
CaSiO3. CaO is produced from limestone
CaCO3 ---→ CaO + CO2
CaO + SiO2 ---→ CaSiO3
The molten slag is less dense than the molten iron and so floats on top of the molten iron. The removal of SiO 2
as slag is an endothermic process and therefore costs fuel. Slag is used to make building blocks and for
manufacturing cement.
The iron produced is not pure as it still contains impurities among which is carbon. This iron is called pig iron.
Pig-iron from the blast furnace contains about 4% carbon. It is strong but very brittle so will not withstand
sharp blows. It is used for street furniture – bollards, drain and manhole covers, for example. If this is remelted,
run into molds, and cooled, it becomes cast iron. This is more brittle and contains much iron carbide, Fe3C.
The carbon content of pig-iron is lowered by blowing oxygen through the molten iron – this oxidises the carbon
to gaseous CO2. If all the carbon is removed, nearly pure iron can be obtained. If some of the carbon is
removed and other metals such as nickel, chromium, manganese, vanadium, etc, are added, the mixture
becomes stronger and is known as steel.
There are various types of steel containing alloyed metals and other elements in various controlled proportions.
Stainless steel consists of an alloy of iron, chromium and nickel: It is expensive so it is not used for largescale construction. It is however used for cutlery, kitchen fittings, surgical instruments, exhaust systems for cars
(at a price)
Stainless steel is attacked by high concentrations of acids. High quality stainless steel is non-magnetic. It will
contain 18% Cr and 8% Ni and is called ’18:8 stainless’
Mild steel contains about 0.15% carbon and is the most widely-used steel. Mild steel is used for almost all nonspecialist steel produce – cars, domestic goods, constructional steel. It rusts easily in presence of air and water,
so alloy steels are used where this is such a serious problem that the much greater coast of alloys is acceptable.
Other types of steel include the following:
Alloy steels are used for various purposes:
Titanium steels are used for cutting tools;
Vanadium steels are used for spanners and springs;
Manganese steel is especially hard and is used for safes;
Alnico contains A1, Ni and Co in addition to iron and is used for permanent magnets.
EXTRACTION OF TIN
Tin is usually extracted from Cassiterite, SnO2 (tinstone). It is usually concentrated by gravity separation and
magnetic separation (to remove magnetic impurities). It is then roasted in air to remove sulphur and arsenic
impurities as volatile oxides, SO2 and As2O3. Iron pyrites are also converted to oxides and sulphides in the
process.
The ore is further concentrated by leaching and washing during which impurities such as CuSO4 and FeSO4 are
washed away, including ferric oxide. The ore is then reduced using carbon, to tin.
SnO2 + C ---→ Sn + CO2(g)
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA
LECTURE NOTES
The tin is drawn into block containing 99.5% tin (called block tin).
SiO2 impurity is removed by CaO (from CaCO3).
CaO + SiO2 ----→ CaSiO3.
The tin is refined/purified by electrolysis.
Tin is a constituent of many alloys including type metal (Sn, Sb, Pb), bronze (Sn, Cu) and solder (Sn, Pb). Large
quantities are used in the manufacture of tinplate as food containers.
ALLOYS
An alloy is a mixture of two or more elements in solid solution in which the major component is a metal. Most
of our metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of
metals as alloys modifies the properties of pure metals to produce desirable characteristics. The aim of making
alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and
luster. Of all the metallic alloys in use today, the alloys of iron (steel, stainless steel, cast iron, tool steel, alloy
steel) make up the largest proportion both by quantity and commercial value. Iron alloyed with various
proportions of carbon gives low, mid and high carbon steels, with increasing carbon levels reducing ductility
and toughness. The addition of silicon will produce cast irons, while the addition of chromium, nickel and
molybdenum to carbon steels (more than 10%) results in stainless steels.
Other significant metallic alloys are those of aluminium, titanium, copper and magnesium. Copper alloys have
been known since prehistory – bronze gave the Bronze Age its name – and have many applications today, most
importantly in electrical wiring. The alloys of the other three metals have been developed relatively recently;
due to their chemical reactivity they require electrolytic extraction processes. The alloys of aluminium, titanium
and magnesium are valued for their high strength-to-weight ratio s magnesium can also provide electromagnetic
shielding. These materials are ideal for situations where high strength-to-weight ratios; magnesium can also
provide electromagnetic shielding. These materials are ideal for situations where high strength-to ratio is more
important than material cost, such as in aerospace and some automotive applications.
Alloys specially designed for highly demanding applications, such as jet engines, may contain more than ten
elements.
DR. J.J. GONGDEN & VEN.(DR). E.J. GONGDEN
UNIJOS-NIGERIA