Metallurgy Flashcards
What is metallurgy ?
Extracting metal from their ores
Difference between metals and non metals ?
A] Lose electron - metals - to form cation - oxidation , gains electron - non metal - to form anion - reduction
b] metals - electron donor , non metals -electron accepter
C] cations - metals , anions - non metals
d] electrovalent compound - metals , covalent compound or electrovalent compound - non metals
e] Metals - Good reducing agent , nonmetals - good oxidising agent
Properties of metals -
Lustrous , malleable , conductivity - Good conductor , density- high , ductility- high ,melting and boiling point - high
Exception for properties of metals -
Melting and boiling point - Na ,K, Hg
Density - Na , K , Ca
Ductility - can be drawn into wires - Exception - Zn , Hg
Malleability - Can be beaten into sheets - Exception -Zn
Oxide Compounds [metals]-
Bauxite - [Al2O3.2H2O]
Zincite- [ZnO]
Haematite-[Fe2O3]
Cuprite-[Cu2O]
Carbonates [Metals] Compounds -
Siderite - FeCO3
Marble - CaCO3
Calamine - ZnCO3
Magnesite -MgCO3
Metals Halides Compounds-
Cryolite - Na3 AlF6
Rock salt - NaCl
Horn silver - AgCl
Fluorspar - CaF2
Metals Compounds Sulphides -
Iron pyrite - FeS2
Zinc Blende-ZnS
Galena - PbS
Cinnabar -HgS
Metals Sulphates compound -
Gypsum - CaSO4.2H2O
Baryte -BaSO4
Epsom salt - MGSO4.7H2O
Anglesite - PbSO4
What is mineral ?
what is ore ?
- The compounds of various metals found in nature - associated with their earthly impurities called minerals
- The naturally Occurring mineral from which metals can be extracted profitably and conveniently
Matrix -
Flux-
Rocky impurities including silica [Sio2] , Mud etc
Substance added to ore to get rid of matrix - resulting in formation of fusible compound - slag
Ores of aluminium -
Bauxite - Al2O3.2H2O -Main ore - Hydrated Aluminium oxide
Cryolite- Na3AlF6 - sodium aluminium fluoride
Corundum -Al2O3 - Aluminium oxide
Ores of Zinc -
Zinc blende - ZnS
Calamine - ZnCO3
Zincite - ZnO
Ores of Iron -
Haematite- Fe2O3 - Iron oxide
Magnetite- Fe3O4 - Tri iron tetra oxide
Iron pyrites -FeS2 - Iron disulphate
Spathic iron ore - FeCO3 - Iron 2 carbonate
Extraction of Aluminium - STEP :1 Ore used- Method used - Process used - Conversion - Reaction -
Bauxite
Chemical method using conc.NaOH
Baeyer’s Process
Al2O3.2H2O –> AL2O3
1ST . IMPURE ORE + NAOH –> 150*C NAALO2 + H20
2ND . SALT ON HYDORLYSIS –> NAOH + AL[[OH]]3
3RD . INSOULUBLE HYDROXIDE –> AL2O3 + H2O
Step 3 extraction of aluminium method process conversion reaction electrolyte electrodes ]reaction
Electrolyte Hall heroult process AL2O3 --> PURE AL ELECTROLYTIC REDUCTION PF AL2O3 FUSED ALUMINIA , CRYOLITE , FLUORSPAR INERT GRAPHIDE CARBON ELECTRODES CATHODE- PURE ALUMINIA ANODE - OXYGEN GAS --> CO CO2 EVOLVED DUE TO OXIDATION OF CARBON ANODE
Seeding means :-
process of adding Al[{Oh]} 3 to further precipitate out AL[{oh}}3
Write down the conversion of bauxite to pure alumina
Al2O3.2H2O + H2O –> NaAlO2 + 3H2O
NaALO2 + 2H2O –> AL[[OH]]3 + NAOH
AL[[OH]]3 IGNITE –> AL2O3 + 3H2O [VAP]
Step -3 reduction of aluminium oxide to alumina -pure Electrolyte- electrolytic cell - electrolytic reaction - products formed -
Cryolite , fluorspar , fused alumina Cathode - carbon lining -gas carbon anode - Thick carbon rod - graphite --> attached to copper clamps dipping into fused electrolyte temp-950* , I - 100Ampere At cathode - 2Al +3 + 6e- --> 2Al At anode - 3O2- - 6e- --> 3[O] --> 3O2
why Al2O3 can’t be reduced to Al by reducing agent ?
Al2O3 is highly stable oxide - and has strong affinity for Oxygen
hence Al2O3 can be reduced to Al electrolytically .
Difficulties faced during electrolytic reduction of Al2O3
Al2O3 has high melting point around 2050C - large amount of electrical energy is required and to maintain Al2O3 at molten state at that temp
liberated Al metal -660C may also tend to volatize out and get wasted
Usage of Cryolite and fluorspar -
Addition of cryolite and fluorspar –> enhances the mobility of the fused mixture
addition of cryolite enhances the conductivity of the mixture
Al2O3 –> is a non conductor
the mixture fuses around 950c instead of 2050*c
WHO REDUCED THE DIFFICULTY FACED DURING REDUCTION OF Al2O3 ?
CHARLES HALL IN 1886
Why layer of powdered coke is used ?
Is sprinkled over the electrolytic mixture
1] prevents burning of carbon electrodes in air
2] minimizes or prevent the heat loss by radiation
why graphite anode should be replaced periodically ?
Oxygen evolved at the anode escapes as gas or react with carbon anode
carbon anode thus oxidised to carbon monoxide which either burns giving carbon dioxide or escapes out through an outlet
hence carbon anode is consumed and renewed periodically
preferable to use number of graphite electrode instead of single one
what happens if concentration of Al2O3 falls ?
Resistance of the bath increases , indicated by glow of bulb
Al can be further purified by
Hoope’s process
Alloys -
substance prepared by adding other metals or non metals - to a base metal in appropriate proportions - to obtain desirable properties
which alloy has base metal mercury ?
amalgam
Aluminium - Alloys-
Duralumin and magnalium
Duralumin - 95% al , 0.5% - Mg Mn , Cu -4%
magnalium - 95% AL , 5% MG
duralumin - al imparts lightness , mg strength
magnalium - light , hard , tough , corrosive resistant
Duralumin and magnalium where they use this two metals
Duralumin –> aircrafts , light tools , cooker
magnalium –> Aircrafts , scientific tools
