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NEET Chemistry Notes General Principles and Processes of Isolation of Metals -Thermodynamics of Metallurgy

NEET Chemistry Notes General Principles and Processes of Isolation of Metals -Thermodynamics of Metallurgy

Thermodynamics of Metallurgy

Thermodynamics of Metallurgy

To understand the variation of temperature requirement for thermal reactions and suitable reducing agent for a given metal oxrde (MxOy), Gibbs energy interpretations are made.
NEET Chemistry Notes General Principles and Processes of Isolation of Metals -Thermodynamics of Metallurgy 1
A reaction with positive ∆G can still be made to occur by coupling it with another reaction having large negative ∆G. Such coupling is easily understood through
Ellingham diagram.
NEET Chemistry Notes General Principles and Processes of Isolation of Metals -Thermodynamics of Metallurgy 2

Gibbs Energy NEET Chemistry Notes General Principles and Processes of Isolation of Metals -Thermodynamics of Metallurgy 3
From Ellingham diagram, it is evident that metals which have more negative NEET Chemistry Notes General Principles and Processes of Isolation of Metals -Thermodynamics of Metallurgy 4 of their oxides can reduce those metal oxides for which NEET Chemistry Notes General Principles and Processes of Isolation of Metals -Thermodynamics of Metallurgy 4 is less negative.
Reduction can also be done by using Al, H2 etc. By Al oxides of Cr, Fe and Mn are reduced. A mixture of Fe203 and Al is called thermite mixture.
Highly electropositive metals like Na, K, Al are reduced by the electrolysis of their fused salts, e.g.
NEET Chemistry Notes General Principles and Processes of Isolation of Metals -Thermodynamics of Metallurgy 5

Occurrence and Principles of Extraction of Some Metals

Some of the important metals, their occurrence and extraction are given below:

Metal Aluminium (Al)
Occurrence

  1. Bauxite-A1203 -2H20,
  2. Cryolite-Na3AlF6

Common method of extraction Electrodes  of A1203 dissolved in molten Na3AlF6 (Hall and Heroult process).

Metal Iron (Fe)
Occurrence .

  1. Haematite-Fe203
  2. Magnetite-Fe304

Common method of extraction Reduction of the oxide with CO and coke in blast furnace.
The iron obtained from blast furnace contains about 4% carbon and many impurities in smaller amount (e.g. S, P, Si, Mn) and is known as pig iron.
Cast iron is different from pig iron and is made by melting pig iron with scrap iron and coke using hot air blast. It has slightly lower carbon content (about 3%) and is extremely hard and brittle.
Wrought iron or malleable iron is the purest form of commercial iron and is prepared from cast iron by oxidising impurities in a reverberatory furnace lined with haematite. This haematite oxidises carbon to carbon monoxide.
NEET Chemistry Notes General Principles and Processes of Isolation of Metals -Thermodynamics of Metallurgy 6

Metal Copper (Cu)
Occurrence

  1. Copper pyrites- CuFeS2
  2.  Copper glance-Cu2S

Common method of extraction Roasting of sulphide partially and auto-reduction.

Metal Zinc (Zn)
Occurrence

  1. Zinc blende or sphalerite-ZnS
  2. Calamine-ZnC03
  3.  Zincite-ZnO

Common method of extraction Roasting followed by reduction with coke.
The metal may be purified by fractional distillation.

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