Metal extraction

see pages 141 and 142 for diagrams on aluminium and iron extractions.

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  • Created by: Jenny B
  • Created on: 15-02-13 16:20
ore?
contains enough of the mineral for it to be worth extracting the metal
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Native?
exist as uncombined metal element
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What affects price of metal?
how comman the ore is/difficulty to extract
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Silver and gold?
Occur naturally as elements
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zinc, iron and copper?
heat with reducing agent like copper or copper monoxide (this is cheapest method)
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Which metals are extracted by electrolysis?
potassium,sodium, lithium, calcium, magnesium,aluminium(all those above zinc)
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problem with electrolysis
very expensive due to large amounts of electricity involved
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some metals extracted by reacting with
more reactive metal but extremely expensive as have to extract the other metal in first place (e.g Titanium)
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main ore of aluminium?
Bauxite
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what is bauxite?
clay mineral which is like impure aluminium oxide
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what happens to the bauxite?
It is treated to form pure aluminium oxide
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What is the alumnium oxide dissolved in?
Molten cryolite
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Why is molten cryolite necessary?
Aluminium oxide has a high melting point, bauxite lowers it and makes electrolysis less expensive
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what is the electrolyte of metal extraction?
aluminium oxide and molten cryolite at about 1000'C
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How many volts does the electrolysis cell operate at?
5-7volts
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what current?
100,000 amps
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How does the electrolyte remain molten?
Heat generated from huge currentt
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Major expense?
large amount of electricity
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How does aluminium form?
Aluminium collects at cathode so sinks to bottom of cell where is can be tapped off. when the molten aluminium is taken fresh aluminium oxide is added.
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Where do the aluminium ions go?
to the cathode and are reduced to aluminium by gaining electrons
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Ionic half-equation for aluminium?
Al3+(l) + 3e- -> Al(l)
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What happens at anode?
Oxide ions are attracted and lose electrons to form oxygen gas
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Ionic half-equation for oxygen?
2O2- (l) -> O2(g) + 4e-
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3 uses of aluminium
Aircraft bodies - low density / pot and pans - shiny and good conductor of heat / power lines - good conductor of electricity and low density
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How is iron extracted?
Blast furnace
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What is added to furnace?
Iron ore, coke and limestone
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What is coke?
impure carbon
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What else is blown into the furnace?
hot air
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What happens to the coke?
coke reacts with oxygen to form carbon dioxide (this is a strongly exothermic reaction)- C(s) + O2(g) ->CO2(g)
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WHat happens to the carbon dioxide?
CO2(g) + C(s) ->2CO(g)
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Why is carbon monoxide important?
Carbon monoxide is the main reducing agent
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Assuming the iron ore is haematite what happens?
Fe2O3(s) +3CO(g) -> 2Fe(l) +3CO2 (g)
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What happens to the iron?
It melts and flows to the bottom of the furnace where is can be tapped off.
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Some of the iron oxide is also reduced by carbon itself in the hotter parts of the furnace
Fe2O3(s) + 3C(s) -> 2Fe(l) + 3CO(g)
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What does the limestone do?
It removes impurities in the ore which would otherwise clog the furnace with solid material
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what does the limestonce undergo does to the high temperatures?
Thermal decomposition (endothermic reaction) must be sure not to add too much limestone or will cool furnace.
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What does the thermal decomposition produce?
CaCO3(s) -> CaO(s) +CO2 (g)
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calcium oxide's function?
To react with acidic oxides like silicon dioxide (SiO2) ,aka quartz, which is a typical sort o impurity that needs to be removed from the furnace
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calcium oxide and silicon equation?
CaO(s) +SiO2(s) -> CaSiO3(l)
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The product is called calcium silicate, what happens to this?
It melts and trickles to the bottom of the furnace as a molen **** which floats on top of the molten iron and can be tapped off separately
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Types of iron?
wrought iron,mild steel, high-carbon steel, cast iron, stainless steel
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What is wrought iron used for?
it is pure iron ; easy to work because fairly soft: decorative work such as gates and railings
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mild steel use?
iron with up to 0.25% carbon; hard and strong: nails,car bodies, ship building,girders
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high-carbon steel use?
iron with between 0.25-1.5% carbon; hard but also brittle: cutting tools, masonry nails
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cast iron
iron with about 4% carbon; very hard but also brittle: manhole covers, guttering,engine blocks
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Stainless steel use?
iron with chromium and nickel; very resistant to corrosion: cutlery, cooking utensils, kitchen sinks
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WHat is pig iron?
Molten iron straight from the furnace that has been cooled rapidly and solidified by running it under sand moulds.
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how is cast iron formed from pig iron?
It is remelted and cooled
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Card 2

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Native?

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exist as uncombined metal element

Card 3

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What affects price of metal?

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Card 4

Front

Silver and gold?

Back

Preview of the front of card 4

Card 5

Front

zinc, iron and copper?

Back

Preview of the front of card 5
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