Embed Size (px)
DESCRIPTION
METALLURGY USEFUL FOR GRADE 8 ,9,AND 10 STUDENTS
Citation preview
METALLURGY
By Tanush Seshadri 8C
RECAP…………
Metals are lustrous, malleable,ductile,sonorous,good conductors of heat and electricity
They are hard They have high densities Due to it’s distinguished properties metals have
a number of uses.(BOTH Physical and Chemical) Metals are extracted from their ‘ores’ Metals are present in the combined form in ‘ores’ This process of extracting metals from their ores
is termed ‘metallurgy’
TERMS TO NOTE
METALLURGY : - The process of extracting a metal in it’s pure state on a large scale from it’s ore by physical or chemical means
ORE : - Ores are minerals from which metals are extracted commercially at low costs with minimum effort.
Amalgam : - An alloy of mercury
PLENARY - 1
Metals form ____________(cations/anions) by _________ electrons.(losing/gaining)
Define METALLURGY Complete the TABLE : -
METAL MINERAL(COMMON)
K,Na
Ca,Mg
Zn,Fe
PLENARY - ANSWERS
CATIONS,LOSING METALLURGY : - The process of extracting a metal
in it’s pure state on a large scale from it’s ore by physical or chemical means
METAL MINERAL(COMMON) K,Na CHLORIDES
Ca,Mg CHLORIDES AND CARBONATES
Zn,Fe OXIDES AND SULPHIDES
NEED FOR METALLURGY-VARIOUS USES OF METALS
Due t o it ‘s properties,metals show many uses Iron is used in war ships because in the form of
steel it has a high tensile strength Copper is used in Boiler pipes and utensils
because it is non reactive Aluminium is used in foil as it is highly malleable Lead is used in X- ray shields as it absorbs
gamma radiations Zinc is used in GALVANIZATION of Fe,being more
electropositive thtan iron(preventing rusting of iron products)
OCCURRENCE OF METALS
METALS occur in the native as well as the combined state : -
Au,Ag,Pt exist in the free state owing to their low chemical activity
IN the COMBINED STATE:- Reactive metals react with certain substances and occur in the combined state in the Earth’s crust due to their HIGH chemical activity.For example sodium ,occurs in the earth’s crust ,in abundance as sodium chloride.(NaCl)
COMPOUNDS OF METALS
Metal Sulphides : -( Metal + Sulphur) generally found in rocks as they are insoluble in water.
Metal halides : - ( Metal + Halogen )Found in oceans and lakes as they are soluble in water
EXTRACTING METALS FROM THEIR ORES
Compounds/Salts of K,Na,Ca,Mg,Al are highly stable and a high amount of energy is required to break them apart.One such way is – ‘electrolysis of the salt/compound in the molten state or aqueous state’
2NaCl (m)2Na + Cl2 1 REDUCING PROPERTY : - Oxides of metals (basic and
amphoteric) can be seperated by the reducing property of coke , hydrogen and other elements.(at high temperatures)
EQUATIONS FOR REDUCING PROPERTY
2ZnS + 3O2 2ZnO + 2SO2
ZnO + C Zn + CO 2FeSO4.7H2O Fe2O3 + SO2 + SO3 +
14H2O 2Fe2O3 + 3C 4Fe + CO2
OR
Fe2O3 + 3H2 2Fe + 3H2O (Zinc oxide can be reduced by coke
only)
THERMAL DECOMPOSITION OF METAL OXIDES
Oxides of metals like Mercury and Silver decompose on heating
2HgO 2Hg + O2
2Ag2O 4Ag + O2
METALLURGY – MECHANICAL SEPERATION
This is brought about by certain machines termed as jaw crushers.These Jaw crushers break down the ore into fine particles,thus increasing the surface area for chemical reactions to take place thereby increasing the speed of the chemical reactions that follow
HYDRAULIC WASHING
PRINICIPLE : - Difference in densities of the metallic ore and the gangue particles
The crushed ore is washed against a stream of water on a vibrating grooved ,sloping table table.The lighter impurities are washed away while the heavier particles remain inside in the groove.
FROTH FLOTATION
Principle : - Different wetting charecteristics of the metallic ore particles and the gangue particles with pined oil and water.The ore is wetted by oil and the gangue by water
Method : - The ore slurry is mixed with a frother(usually pine oil) and a collector(usually ethyl xanthate) in a large tank .The collector mmakes the ore particles water repellent.The whole mixture is aagitated with air.
The oil coated ore,being lighter than the water coated impurities,forms a froth and rises to the surface of the tank.IT IS THEN SKIMMED OFF.
The gangue cling on to the water and settle down NOTE :- THIS IS MAINLY USED FOR SULPHIDE ORES
MAGNETIC SEPARATION
PRINCIPLE : -When either the gangue or the metallic particles are magnetic while the other is non magnetic
The crushed ore is dropped over on a leather conveyor belt which passes over two rollers on of which is magnetic.
The non magnetic particles fall due to the pull of gravity.
The magnetic particles cling on for a longer time the belt as they are attracted to the magnetic roller and fall later
Both the particles are collected in two separate dishes
Roasting Calcination Ore is heated
strongly in the presence of air
Used for Sulphide ores.Hence Sulphur dioxide is given out
Volatile impurities are removed as oxides
Ore heated in the absence of air
Used in carbonate or hydrated ores,hence Carbon dioxide or water vapour is given out.
Moisture,organic impurities are removed.(even volatile)
Similarities between the two Both the processes are carried out in a
reverberatory furnace. Both these processes convert the ore to
it’s metal oxide They make the ore porous by removing
volatile impurities from them.
ROASTING
BAYER’S PROCESS (Concentration of Bauxite-ore of Aluminium)
Bauxite is crushed and then washed to remove dirt.It is then ground to a fine powder and heated to remove volatile impurities.
* Caustic Soda(NaOH) solution is added to the crushed bauxite to give Sodium Aluminate and Water.(Mixture is heated under pressure for 2-3hrs) in a digester
Insoluble impurities are removed by FILTIRATION **The filtrate Sodium Aluminate is then cooled and diluted
with acidulated water(HCl) in a tank called a precipitator.It undergoes hydrolisis and Al(OH) 3
IS given out .The prrecipitation process is sppeded up by adding aluminium hydroxide crystals.This is called seeding.
* **Aluminium hydroxide is washed, dried and ignited to given pure alumina (Aluminium Oxide)
EQUATIONS IN BAYER’S PROCESS CONVERSION OF Bauxite (powder)to Sodium
Aluminate Al2O3.2H2O + 2NaOH 2Na AlO2 + 3H2O Conversion of Sodium Aluminate to
Aluminum Hydroxide by hydrolysis at a temperature of 30-600C
NaAlO2 + HCl + H2O NaCl + Al(OH)3
Conversion of the precipitate- 11000C(Aluminum Hydroxide)
2Al(OH)3 Al2O3 + 3H2O
VIDEO :- BAYER’S PROCESS EXPLAINED
http://www.youtube.com/watch?v=ZtHF8zyR32Q
REDUCTION METAL OXIDES
In various methods ,the Oxide of the metal is obtained.The last step to obtain the metal is by reduction by Coke,Hydrogen or Carbon Monoxide(in some cases only)
Based on position in the reactivity series,themethod of reduction may be by heating,by use of Coke or CO or by electrolysis.
(REDUCTION FOR OXIDES BELOW Al and electrolysis for oxides above Al)
Reduction of metal oxides by Coke/CO
Oxides of Zn,Pb,Sn,Cu can be reduced by this method . The bye – product is CO if Coke is used or Carbon dioxide if CO is used
PbO + C Pb + CO CuO + CO Cu + CO2
(Heating required)
Aluminothermy(Aluminium + Heat) Oxides of Cromium and Manganese have a
greater affinity for oxygen than coke and hence cannot be reduced by it.Alumnium has a great affinity for oxygen and hence it can be used for extracting the metal from it’s oxides in the presence of heat
The process BY which a metal oxide is extraxted by the reduction of it by Aluminium by heating is called Aluminothermy.It is an exothermic reaction has a lot of heat is given out.
REDUCTION by heat
Galena (PbS) is roasted to form Lead oxide and Sulphur dioxide.This Lead oxide is mixed with Galena and stringly heated to give Lead and Sulphur dioxide
Mercury is obtained from cinnabar(HgS) by heating the ore in the presence of Oxygen.Mercuric oxide is obtained and Sulphur dioxide is released.Mercuric oxide is heated at a temperature above 300 degress Celsius to give Mercury and Oxygen
Electrolytic Reduction
Reactive metals which are strong reducing agents themselves are reduced by passing electric current through the purified molten ore.
The molten oxide or Chloride is placed in an electrolytic cell with cathode and Anonde.Cathodes attract cations and Anodes attract anions
The compound is heated to melt.They can conduct elctricity.The metal is deposited at cathode(which has negative charge) from where it is separated
Simuntaneously the Non metal is deposited and is converted from the ion to the non metal
Proces by which a metal is decomposed to give the corresponding IONS is called ionisation
Refining the Metal
Metal obtained is sometimes contaminated with metals and other non metals.Hence purification is required
ELECTROLYTIC refining : -During electrolysis the pure metal is dedposited at the cathode
Impurities from the anode fall down and collect down at the bottom of the tank as anode mud
The impurities in the anode mud are either more reactive or less reactive than the metal to be refined
More reactive metallic impurities pass into the electrolyte solution
Less reactive metals collect as anode mud and are recovered from there.
Advantages
Metal is purified Valuable metals present as impurities
can be recovered.
PLENARY - 2
Given below are some metals K,Na,Ag,Al,Cu,Ca,Hg,Pb,Zn State which metal(only 1) would be
separated by Electrolysis Reduction of oxide by hydrogen Reduction by coke Thermal decomposition of metal oxideGive equations for the above
Tabulate the differences and similarities between Roasting and Calcination
Write an equation/s for extracting A metal from limestone.State the method.
Explain Hydraulic Washing Mention the methods( physical and chemical )by which
sulphide ores can give the corresponding metal If a Copper ore is used will the gangue particles be
magnetic or non magnetic , if they are to be separated by Magnetic separation?
Calcium is extracted from limestone.Suggest a suitable methodd for it’s extraction.Give reasons for your answer
Why is Gold found in the native state?
An element X combines with Oxygen to form X O.This element reacts with a basic oxide to form salt and water and reacts with carbon dioxide to form salt and water.Element X is highly malleable and shows many applications like foil.
Identify Element ‘x’.State if it is a metal or non metal
What type of oxide did it form? Aluminium cannot be reduced by COKE.Explain
Why? Define seeding. Write equations for Bayer’s process.
Which is the odd one out and why? Hematite: Ilmenite: Magnetite: Malachite:
Which is the odd one out and why? Hematite: Ilmenite: Magnetite: Malachite: Malachite because it is an ore of copper
and the rest are ores of iron.
Which is the odd one out and why? Froth Flotation Magnetic Separation Hydraulic washing Calcination
Which is the odd one out and why? Froth Flotation Magnetic Separation Hydraulic washing Calcination Calcination because it is a chemical
process while rest are physical processes and they only separate ore from impurites(gangue)
Which is the odd one out and why? Sodium Pottasium Aluminium Lead
Which is the odd one out and why? Sodium Pottasium Aluminium LeadLead because it’s oxide can be reduced by
Hydrogen,Coke or,CO while the rest cannot
MORE INFO ON ORES and other stuff…
http://en.wikipedia.org/wiki/Ore http://www.amateurgeologist.com/ores-o
f-common-metals-collection.html
http://www.scs.illinois.edu/~mainzv/HIST/bulletin_open_access/num17-18/num17-18%20p15-19.pdf
http://www.youtube.com/watch?v=6nEt6cW_GSw
http://www.youtube.com/watch?v=_OrBw4L490Y
