1. TRANSITION AND INNER TRANSITION ELEMENTS
PRESENTE
D BY:
FREYA
CARDOZO
BY FREYA CARDOZO
2. TRANSITION ELEMENTS
THE GENERAL ELECTRONIC CONFIGURATION OF TRANSITION ELEMENTS IS
(N-1)D1-10 NS1-2.
THE TRANSITION ELEMENTS ARE PLACED IN THE PERIODS 4 TO 7 AND GROUPS 3 TO 12
THOSE CONSTITUTE 3D,4D,5D AND 6D SERIES
BY FREYA CARDOZO
3. WHAT ARE TRANSITION ELEMENTS
Elements that have a partially filled d orbital in their ground state or one of its oxidation state.
G.R why Zn is not a transition element but Cu is.
Since zinc has completely filled (n - 1)d orbital in the ground state (3d104s2) and (3d10) in its common
oxidation state +2, it is not regarded as transition element.
Copper in the elementary state (3d104s1) contains filled 3d orbitals but in the +2 oxidation state it has partly
filled 3d orbital (3d9), hence copper is a transition element.
BY FREYA CARDOZO
6. GIVE REASON
Why Cu and Cr show anomalous E.C
Mainly due to the fact that half filled and fully filled orbitals have extra stability
The general electronic configuration of the elements of the 3d series is 3d1-10 4s2 with the exceptions of
Cr and Cu.
The 3d and 4s orbitals are close in energy and in order to gain extra stability the last electron instead of
occupying 4s orbital occupies the 3d orbital that assigns Cr the 3d5 4s1 and Cu 3d10 4s1configuration
BY FREYA CARDOZO
7. PHYSICAL PROPERTIES
They are hard, lustrous, malleable and ductile
They are good conductors of heat and electricity
They possess high MP BP
Except Zn, Cd, Hg and Mn, all the other transition elements have one or more typical metallic structures
at ambient temperature.
These transition metals (with the exception of Zn, Cd and Hg) are very hard and have low volatility
BY FREYA CARDOZO
8. IONIC RADIUS
For the same oxidation state, with an increase of nuclear
charge a gradual decrease in ionic radii was observed.
The trend is pronounced for the divalent ions of the first
transition series (Cr2⊕ - 82 pm, Cu2⊕ - 72 pm).
The oxidation states of the same element shows
difference of one unit such as M⊕, M2⊕, M3⊕,M4⊕ and so
on.
With higher oxidation state the effective nuclear charge also
increases and hence, decrease of ionic radii can be observed
from M2⊕ to M3⊕
BY FREYA CARDOZO
9. ATOMIC RADII DECREASES GRADUALLY
ACROSS THE PERIOD
As we move across a transition series from left to right the nuclear charge increases by one unit at a
time.
The last filled electron enters a penultimate (n-1)d subshell.
However, d orbitals in an atom are less penetrating or more diffused and, therefore d electrons offer
smaller screening effect.
The result is that effective nuclear charge also increases as the atomic number increases along a
transition series.
Hence the atomic radii decrease gradually across a transition series from left to right.
BY FREYA CARDOZO
Size decreases across a period
10. IONIZATION ENTHALPY
The I.E for d block elements lies between the s and p blocks
Across the group as the size decrease
Ionization enthalpy increases
IE3>IE2> IE1
Depending on condition the type of bond is decided
Lower O.S – Ionic bond
High o.s – Covalent bond
BY FREYA CARDOZO
Ionization energy or Ionisation
energy, denoted Eᵢ, is the minimum
amount of energy required to
remove the most loosely bound
electron, the valence electron, of an
isolated neutral gaseous atom or
molecule
Size decreases across a
period
I.E ↑
Acros
s the
period
11. IONISATION ENTHALPY
G.R ionization enthalpy for 3rd transition series is
more than 1st and 2nd series
The atoms of elements of third transition series
possess filled 4f- orbitals. 4f orbitals show poor
shielding effect on account of their peculiar diffused
shape.
As a result, the valence electrons experience greater
nuclear attraction.
A greater amount of energy is required to ionize
elements of the third transition series
BY FREYA CARDOZO
12. METALLIC CHARACTER
Metallic character is due to the :
1. VACANT d orbitals
2. Low ionisation enthalpy
Hardness of metals is due to the covalent bond which is possible because of the unpaired (n-1)d
electrons in these elements
Mostly they show HCP, ccp, bcc lattice structure
Hardness, high melting points and metallic properties of the transition elements indicate that the metal
atoms are held strongly by metallic bonds with covalent character.
BY FREYA CARDOZO
13. MAGNETIC PROPERTIES
They show magnetic properties due to the unpaired electrons
3 types
1. Dimagnetic – Replled by magnetic field
2. Paramagnetic- attracted to mag field
3. Ferromagnetic- strongly attracted. EG. Fe, Co, Ni
Magnetic moment is sum of spin angular momentum and orbital angular momentum
µ= n(n + 2) BM
n = no.of unpaired ELECTRONS
BY FREYA CARDOZO
Paired e- : Diamagnetic
Unpaired e-:
Paramagnetic
14. QUESTIONS
Which one of the following is dimagnetic
a. Cr2⊕ b. Fe3⊕
c. Cu2⊕ d. Sc3⊕
Magnetic moment of a metal
complex is 5.9 B.M. Number of
unpaired electrons in the complex is
a. 2 b. 3
c. 4 d. 5
BY FREYA CARDOZO
15. QUESTIONS
What is the magnetic moment for Cr3+
a. equal to 1.73 BM,
b. less than 1.73 BM or
c. more than 1.73 BM ?
Why salts of Sc3⊕, Ti4⊕, V5⊕ are colourless ?
Calculate the spin only magnetic moment of divalent cation of a transition metal with atomic number 25.
BY FREYA CARDOZO
18. A substance appears coloured if
it absorbs a portion of visible light. The colour
depends upon the wavelength of absorption in
the visible region of electromagnetic radiation
BY FREYA CARDOZO
19. REASONS FOR COLOR IN TRANSITION METALS
1. presence of unpaired d electrons
2. d - d transitions
3. nature of ligands attached to the metal ion
4. geometry of the complex formed by the
metal ion
BY FREYA CARDOZO
20. UNPAIRED ELECTRONS AND D-D TRANSITION
REASON FOR COLOUR- d-d transition
BY FREYA CARDOZO
21. GEOMETRY OF COMPLEX ION
When cobalt chloride (Co2⊕) is dissolved in water, it forms a pink solution of the complex
[Co(H2O)6]2⊕ which has octahedral geometry.
But when this solution is treated with concentrated hydrochloric acid, it turns deep blue.
This change is due to the formation of another complex [CoCl4]2 which has a tetrahedral structure.
BY FREYA CARDOZO
22. CHARGE TRANSFER
MnO4- ion has an intense purple colour in solution.
In MnO4- , an electron is momentarily transferred from oxygen (O) to metal, thus momentarily changing
O2 to Oand reducing the oxidation state of manganese from +7 to +6.
For charge transfer transition to take place, the energy levels of the two different atoms involved should
be fairly close.
Colours of Cr2O7
2- , CrO4 , Cu2O and Ni-DMG (where DMG = dimethyl glyoxime) complex are other
examples
BY FREYA CARDOZO
23. CATALYTIC PROPERTIES
because of their ability to participate in different oxidation-reduction steps of catalytic reactions.
This possible due to
1. unpaired e-s in incomplete d orbitals
2. variable o.s
3. Large surface area
In homogeneous catalysis reactions, the metal ions participate by forming unstable intermediates.
In heterogeneous catalysis reactions on the other hand, the metal provides a surface for the reactants to
react.
BY FREYA CARDOZO
24. EXAMPLES OF IMPORTANT CATALYST
Mo/Fe – Habers process
Co-Th Fischer Tropsch process --- gasoline synthesis
Ni – cataylic hydrogenation
Platinised asbestos- solid catalyst --- contact process for manu of sulfuric acid from SO2 and O2
Fe-Cr – production of CO2 frm CO
BY FREYA CARDOZO
25. INTERSTITIAL COMPOUNDS
When small atoms like hydrogen, carbon or nitrogen are trapped in the interstitial spaces within the
crystal lattice, the compounds formed are called interstitial compounds
Steel and cast iron are examples of interstitial compounds of carbon and iron
Properties
1. Good conduction
2. MP BP higher than parent
3. Density less than parent
carbides of metals are inert and hard
hydrides of transition metals are Powerful reducing agents
BY FREYA CARDOZO
26. ALLOYS
Alloys are mixtures of metals
classification
1. Ferrouss alloys have atoms of other elements distributed randomly in atoms of
iron in the mixture.
As percentage of iron is more, they are termed ferrous alloys eg. nickel steel,
chromium steel, stainless steel etc. All steels have 2% carbon
2. Non-ferrous alloys are formed by mixing atoms of transition metal other than iron
with a non transition element.
eg. brass, which is an alloy of copper and zinc. Ferrous and non-ferrous alloys are
of industrial importance.
BY FREYA CARDOZO
27. USES
Bronze=Cu+Tin Tough, strong and corrosion resistant
Cupra nickel – machine parts of ships
stainless steel – air crafts
Nichrome=Ni+Cr – turbine engines
Titanium alloys --- can withstand high temp
Components of Nichrome alloy are
are
a. Ni, Cr, Fe b. Ni, Cr, Fe, C
c. Ni, Cr d. Cu, Fe
BY FREYA CARDOZO
28. PREPERATION OF POTASSIUM DICHROMATE
K2CR2O7
1. Chromite ore =FeO.Cr2O3 to Sodium chromate Na2CrO4 --- anhydrous
sodium carbonate And flux of like in air
2. Sodium chromate to Sodium dichromate Na2Cr2O7 ---- Sulphuric acid
and water
3. Sodium dichromate to potassium dichromate K2Cr2O7 --- Potassium
chloride
BY FREYA CARDOZO
FeO.Cr2O3
Na2CrO4
Na2Cr2O7
K2Cr2O7
OUTLINE
32. CHEMICAL PROPERTIES OF POTASSIUM
DICHROMATE
Reactant Colour
(Before)
K2SO4 Cr2(SO4)3 H2O Special
byproduct
Color
K2Cr2O7+H2SO
4
KI
Potassium
iodide
Orange ✓ ✓ ✓ I2 Brown
K2Cr2O7+H2SO
4
H2S
Hydrogen
sulphide
Orange ✓ ✓ ✓ S Green
solution
+
Yellow
ppt
BY FREYA CARDOZO
33. REACTION WITH KI
The oxidation of KI with acidified potassium dichromate produces I2
This changes the solution to brown
Potassium dichromate is reduced to chromic sulphate
BY FREYA CARDOZO
34. REACTION WITH H2S
The reaction leads to the pptn of S which appears as pale yellow ppt
Potassium dichromate is reduced to chromic sulphate
Due to the production of chromic sulphate the orange solution turns green
BY FREYA CARDOZO
35. KMNO4 – POTASSIUM PERMANGANATE
Preparation method
1. Chemical oxidation
2. Electrolytic oxidation
BY FREYA CARDOZO
36. CHEMICAL METHOD
MnO2 manganese dioxide K2MnO4 Potassium mangante(green) –
1. Caustic potash KOH
2. Potassium chlorate KClO3 – oxidising agent
Dispropotionation in neutral or acidic medium KMnO4 + MnO2
Filteration to glass wool
BY FREYA CARDOZO
37. ELECTROLYTIC OXIDATION
Alkaline solution of manganate ion is electrolysed between iron electrodes seperated by a diaphram
At anode the oxygen evolved is used to reduce manganate to permanganate
Overall reaction
The solution is evaporated and filtered to obtain the crystals
BY FREYA CARDOZO
38. CHEMICAL PROPERTIES OF KMNO4
In acidic medium- Oxidising action
1. Iodide to Iodine
2. Fe2+ to Fe3+
3. H2S to S
4. Oxidation of oxalic acid H2C2O4
In neutral medium or weakly alkaline medium
1. Iodide to Iodate
2. Oxidation of thiosulphate to sulphate
3. Manganous salt to manganese dioxide
BY FREYA CARDOZO
42. USES
Antiseptic
Test for unsaturation
Quantitative analysis- Halide detection
Volumetric analysis- For reducing agents
Oxidising agent- labs and industry
Why is KMnO4 such a good oxidising agent?
BY FREYA CARDOZO
44. INNER TRANSITION ELEMENTS
Orbital lies much inside the d orbital,in relation to the transition metals the f
block elements are called inner transition elements.
f – 1 to 14 electrons, d – 0 or 1 and s – 2 electrons
2 series : Lanthanoids and Actinoids
Lanthanoids – characterizied by filling of 4f
Actinoids - characterizied by filling of 5f
14 elements in each
BY FREYA CARDOZO
45. F BLOCK ELEMENTS
Those elements in which the outermost electrons enter the f subshell
They belong to the 6th and 7th period
Placed seperately at the bottom of the table
BY FREYA CARDOZO
46. PROPERTIES OF F BLOCK ELEMENTS
These metals are soft with moderate densities of about 7 g cm-3.
They have high melting point
They are quite reactive similar to the alkali metals than d block metals
common oxidation state for lanthanoids is +3
+2 is also very common among these, higher O.S like +4 is unusual (exptn- Ce)
BY FREYA CARDOZO
47. LANTHANOIDS- RARE EARTH ELEMENTS
They were know as rare because it was difficult to extract them economically from their ores
BY FREYA CARDOZO
48. G.R: LANTHANOIDS HAVE LOWER HEAT OF
ATOMIZATION THAN TRANSITION METALS.
The energy required to break up the metal lattice is heat of atomization.
This is because with d electrons, transition metals
are much harder and require high heat of
atomization.
Europium and ytterbium have the
lowest enthalpies of vaporization and largest
atomic radii of lanthanoids, resemble barium.
BY FREYA CARDOZO
49. RADII
Their ionic radii decrease from 117 pm of La to 100 pm for Lu.
This is because 5f orbitals do not shield the outer 5s and 5p electrons
effectively, leading to increase in effective
nuclear charge and decrease in the ionic size.
BY FREYA CARDOZO
50. REACTIONS WITH LN
Reactants Reactants Product
Ln C LnC
Ln H2O Ln(OH)3
Ln O2 Ln2O3
Ln N2 LnN
Ln X LnX3
Ln= Lanthanoids
BY FREYA CARDOZO
51. BASICITY OF LANTHANOIDS
All the lanthanoids form hydroxides ofthe general
formula Ln(OH)3
These are ionic and basic.
Since the ionic size decreasesfrom La3+ to Lu3+,
the basicity of hydroxides decreases.
La(OH)3 is the strongest base while Lu(OH)3 is the
weakest base.
BY FREYA CARDOZO
52. ELECTRONIC CONFIGURATION
Generally the E.C for lanthanoids is represented as [Xe] 4f0-14 5d0-1 6s2
Xe = Xenon, Z= 54
The E.C for Xe is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10
BY FREYA CARDOZO
53. EXCEPTIONS
The electrons first fill up the 6s
4f and 5d are very close in energy
In case of lanthanum the 5d oribtal has lower energy
In case of Gd and Yb the anamolous behaviour is
observed
As half filled and fully filled electrons have extra stability
Thus general E.C for lanthanoids is [Xe] 4f0-14 5d0-1 6s2
BY FREYA CARDOZO
54. IONISATION ENTHALPY
What is ionisation enthalpy?
As size increases, ionisation enthalpy decreases since the
last electron experiences lesser pull from the nucleus
Across the period, size decreases thus I.E increases
Why some elements have variable O.S states but others only
a few? Can ionisation enthalpy justify these?
BY FREYA CARDOZO
55. QUESTION
HINT:
-Energy required to remove unpaired electrons is lesser than that
to remove paired electrons
- Check the energy of subshell, lower the energy easy to remove
the last electron
- n+l lower: lesser energy the subshell has
BY FREYA CARDOZO
56. OXIDATION STATE
G.E.C = [Xe] 4f0-14 5d0-1 6s2
thus the common O.S is +3 i.e 2 e- from 6s and the order from d/f
subshell
The 4f electrons are shielded by the inner 5s and 5p orbitals, they are
tightly bond to the nucleus. Thus they do not take part in the bonding
Some show O.S +2 and +4 this is due to f0, f7, f14 E.C
BY FREYA CARDOZO
57. COLOUR
These elements are coloured due to the f-f
transition which corresponds to the energy in
the visible spectrum
The colour of ions with nf electrons= (14-n)f
electrons
COLOUR IN LANTHANOIDS
BY FREYA CARDOZO
58. WHAT IS SHIELDING EFFECT
The decrease in the net force of attraction between
the electrons present in the outer shell of an atom in
the direction of nucleus due to change in linearity of
the electric lines of forces between them due to the
presence of high election density in the inner shells
in the same atom is known as screening effect.
BY FREYA CARDOZO
59. ATOMIC RADII
Across the period the radii decreases as the size
decreases
The decrease in lanthanoids is very steady this is
called the LANTHANOID CONTRACTION
As we move left to right the nuclear charge
increases by +1 and an electron is added
The electron is added to the same 4f subshell
Due to their diffused shape the 4f electrons shield
each other poorly from the nuclear charge
With increasing atomic no. the effective nuclear
charge increases thus pulling the 4f shell closer,
causing it to cntract
BY FREYA CARDOZO
60. MAGNETIC MOMENT
µ=square root of n(n + 2) BM
n = no.of unpaired ELECTRONS
Calculate magnetic moment for La3+
La -57
[Xe]4f05d16s2 n=1
Magnetic moment
BY FREYA CARDOZO
61. APPLICATIONS
In hybrid cars, superconductors and permanent magnets
Used in the colour tubes of computers and T.Vs since they
produce visible light over a small wavelength upon bombarding
with e-s
(Eu,Y)2O3 – red colour
There types of Ln are used to get 3 primary colours
Luminescent materials Nd: YAG laser
Applications of Lanthanoids
BY FREYA CARDOZO
63. ACTINOIDS
Starts with Thorium Z=90 and ends with Lawrencium Z=103
They are all radioactive and man-made
High M.P, B.P, density
The electronic configuration of actinoids is
[Rn] 5f0-14 6d0-2 7s2, where Rn is the electronic
configuration of radon.
most stable oxidation state in actinoids
is +3. The highest however actinoids show a variety of O.S from +2 to +8
BY FREYA CARDOZO
65. OXIDATION STATE
Early lanthanoids show variable O.S this is similar to transition
elements than lanthanoids
This pattern is seen mostly due to the ability of 5f orbital to
participate in bonding
A ready loss of 5f electrons by early actinoids indicates that these
electrons are much closer in energy to 7s and 6d electrons than
the 4f electrons to 6s and 5d electrons as in lanthanoids
G.E.C [Rn] 5f0-14 6d0-2 7s2
Eg. uranium has electronic configuration of [Rn]7s2 5f 36d1. The
formation of +6 oxidation state corresponds to an electronic
configuration of [Rn].
BY FREYA CARDOZO
66. Half filled and fully filled
orbitals have extra stability.
Thus one electron from f is
promoted to d
BY FREYA CARDOZO
67. The overall gradations
among the different blocks
of the periodic table
Transition elements- d
block
Lanthanoids-f block
Pre- transition – s block
BY FREYA CARDOZO
68. ACTINOID CONTRACTION
5f 6d 7s are almost same energy in actinoids
The 7s electrons shield the 5f and 6d orbitals from nuclear
charge , thus they expand a little. Therefore, they have size
greater than lanthanoids
But the decreases in radii is not as prominent, due to the
shielding effect of f orbitals
BY FREYA CARDOZO
69. APPLICATION OF ACTNOIDS
Half lives of Thorium & Uranium are so long that
the amount of radiation emitted is negiligble, thus
they can be used in everyday life.
Th(IV) oxide, ThO2 with 1% CeO2 was used as a
major source of indoor lighting before
incandescent lamps came into existence only
because these oxides convert heat energy from
burning natural gas to an intense light.
Even today, there is a great
BY FREYA CARDOZO
70. POSTACTINOID ELEMENTS
POST ACTINOID ELEMENTS
Elements with atomic number greater than 92 are called ‘Transuranium’.
Elements from atomic number 93 to 103 now are included in actinoid series and
those from 104 to 118 are called as postactinoid elements.
They are included as postactinoids because similar to actinoid elements, they can
be synthesized in the nuclear reactions.
So far, nine postactinoid elements have been synthesized.
Half life is in secs 2.8 x 10^-4, thus difficult to study reactions
Rutherfordium forms a chloride, RfCl4, similar to zirconium and hafnium in the +4
oxidation state.
Dubnium resembles to both, group 5 transition metal, niobium(V) and actinoid,
protactinium(V).
BY FREYA CARDOZO
71. Questions
ix. In which of the following series
all the elements are radioactive in
nature
a. Lanthanides b. Actinides
c. d-block elements d. s-block elements
x. Which of the following sets of ions
contain only paramagnetic ions
a. Sm3⊕, Ho3⊕, Lu3⊕ b. La3⊕, Ce3⊕, Sm3⊕
c. La3⊕, Eu3⊕, Gd3⊕ d. Ce3⊕, Eu3⊕, Yb3⊕
xi. Which actinoid, other than uranium,
occur in significant amount
naturally?
a. Thorium b. Actinium
c. Protactinium d. Plutonium
BY FREYA CARDOZO
73. DEFINITION
Mineral : naturally occuring substance found in the earth’s crust containing inorganic salts, solids,
siliceous matter etc, is called a mineral.
Ore: The mineral which contains high percentage of the metal and from which the metal can be
extracted economically is called an ore
DEFINITONS
BY FREYA CARDOZO
75. TYPES OF METALLURGY
Pyrometallurgy: A process in which the ore is reduced to
metal at high temperature using reducing agents like carbon,
hydrogen, aluminium, etc. is called pyrometallurgy.
Hydrometallurgy : The process of extracting metals from the
aqueous solution of their salts using suitable reducing agent
is called hydrometallurgy.
Electrometallurgy : A process in which metal is extracted by
electrolytic reduction of molten (fused) metallic compound is
called electrometallurgy
TYPES OF METALLURGY
BY FREYA CARDOZO
76. GENERAL METHODOLOGY
Extraction of ore
Concentration of ore – removing impurities of other metals, sand, dust
particles
impurities termed as gangue are removed from the ore and the ore gets
concentrated.
The sand, mud and other unwanted impurities which remain mixed with the
ore deposit are called gangue.
Methods –
1. Hydraulic classifiers
2. Froth floation
3. Magnetic seperation
Convert to its oxides – Can be done by either
1. Roasting .
2. Calcination
Obtaining pure metal
BY FREYA CARDOZO
78. EXTRACTION OF IRON
Ore – Haematite ore (Fe2O3)
Gangue -SiO2 + Al2O3+ phosphates
Concentration – Hydraulic classifier
The powdered ore is washed in a powerful current of water introduced
into the hydraulic classifier.
The lighter gangue particles are separated and the concentrated ore is
collected at the bottom.
Converting into the oxide
Roasting : The concentrated ore is heated In a current of air. The sulfur
and arsenic impurties present in the ore get converted into their oxides
and escape as vapour. Ferrous oxide in the ore is converted to Fe2O3
4FeO + O2 -- 2 Fe2O3
STEPS IN EXTRACTION OF Fe ore
BY FREYA CARDOZO
81. BLAST FURNANCE- Smelting
Tall cylindrical steel tower lined with
refractory bricks.
The height=25 m and diameter =5 to10
m.
Working- counter current principle :
Charge comes down and hot gases move
up the tower.
The furnace is comprised of 3 parts –
1. Hearth, 2. Bosh and 3. Stack
Ore is introduced in the furnace through
a cup and cone arrangement
Ensures uniform distribution and
prevents loss of gases
A blast of preheated air is introduced into
the furnance below the bosh through
BY FREYA CARDOZO
83. 1.ZONE OF COMBUSTION
The formation of CO is exothermic and thus temperature is 2000K
Some CO decomposes to C
The hot CO gas moves upward and thus heats up the incoming charge
Therefore CO acts as a fuel and reducing agent
BY FREYA CARDOZO
85. ZONE OF SLAG FORMATION
The gangue present in the ore is converted to slag. This slag can be used for making road foundation.
Temperature of this zone is 1200 K. The gangue contains silica, alumina and phosphates. A removal of this
gangue is effected by adding lime-stone in the charge, which acts as flux. Limestone decomposes to give
CaO (quick lime)
3.Zone of slag formation
BY FREYA CARDOZO
86. • ZONE OF FUSION
MnO2 and Ca3(PO4)2 present in the iron ore are reduced to Mn and P. Some of the silica is also reduced to
Si.
The spongy iron coming down in the furnace melt absorbs impurities like C, Si, Mn, P and S. This molten
iron collects at the bottom in the furnace.
The slag which is lighter floats on the surface of molten iron. Molten slag and iron are collected through
separate outlets.
Molten iron is poured into moulds.
These solid blocks are called pigs. This iron contains about 4% of carbon.
When pig iron is remelted, run into moulds and cooled, it becomes cast iron. The waste gases containing
N2, CO and CO2 escape through the outlet at the top. These hot gases are used for preheating
the blast of air
BY FREYA CARDOZO
88. FACTORS AFFECTING EXTRACTION TECHNIQUE
Pure iron can be obtained by electrolytic refining of impure iron or other methods given in the flow chart.
The choice of extraction technique is governed by the following factors.
1. Nature of ore
2. Availability and cost of reducing agent, generally cheap coke is used
3. Availability of hydraulic power.
4. Purity of product (metal) required.
5. Value of byproducts for example, SO2 obtained during roasting of sulphide ores is vital for manufacture
of H2SO4. Knowledge of electrochemical series provides solutions to many problems.
BY FREYA CARDOZO
