Section 1
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What is coke?
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Last updated
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Date created
Mar 1, 2020
Cards (83)
Section 1
(50 cards)
What is coke?
impure carbon
When is iron oxide reduced by C itself?
in the hotter parts of the furnace
How are Al cables strengthened?
core of steel
What is roasting?
heating a compound in air to form an oxide
How can the metal then be obtained from the oxide?
must be reduced NEED TO ADD ELECTRONS!
What is the electrolyte?
solution of aluminium oxide dissolved in molten cryolite
What happens first to the limestone that is put in the furnace? What type of reaction is this?
V.Hot temperatures in the furnace so the limestone undergoes thermal decomposition to form calcium oxide and carbon dioxide CaCO₃ → CaO + CO₂ ENDOTHERMIC
unreactive metals found...
native - so unreactive that they are found naturally as the uncombined element
What is the issue with aluminium oxide?
HIGH MELTING POINT NOT PRACTICAL TO ELECTROLYSE THIS MOLTEN AS LOTS OF ENERGY IS NEED TO MELT IT
How is Al extracted?
ELECTROLYSIS - FAIRLY REACTIVE METAL
What is the iron straight from the furnace?
pig iron
What happens to the hot waste gases at the top of the furnace?
piped away used to heat the air blast at the bottom
What is the blast furnace diagram?
What is the main reducing agent in the furnace and where?
CO especially in the cooler parts
What does cryolite do?
it is another aluminium compound that melts at a more reasonable mixture and so allows for the Al2O3 to melt at a lower temp LOWERS COSTS
What temp is the solution of pure aluminium ore and molten cryolite?
about 1000 degrees
What two factors govern the method used for extraction?
cost of... ENERGY REDUCING AGENT
Why did the Al age not occur very early on?
because Al is above C in the RS so it cannot be made accidently by reacting Al₂O₃ WITH Carbon - needed to be extracted using electricity which was only discovered much later
When is the CO2 reduced by more C?
in the very hot parts of the furnace
How else can metals be extracted (Ti)?
heat the compound with a more reactive metal
How does CaO remove silicon dioxide?
CaO + SiO₂ → CaSiO₃
Why would silicon dioxide clogging the furnace be an issue?
furnace would have to be shut down whilst solid is removed VERY COSTLY
Why is electrolysis not ideal?
lots of electricity = EXPENSIVE PROCESS Therefore the metal product is also expensive to then buy
How is a sulfide like zinc blende (sphalerite) converted into an oxide?
heated in air 2ZnS + 3O₂ → 2ZnO + 2SO₂
What happens to this product? What is the common name?
melts and trickles to the bottom of the furnace as a molten SLAG which floats ontop of the molten iron and is tapped off separately ROAD BUILDING AND FERTILISER
Why is carbon used?
cheap source of heat
Extract metals zinc and below?
heat with C/CO REDUCING AGENT
What are the stages of the extraction of iron?
C + O₂ → CO₂ CO₂ + C → 2CO Fe₂O₃ + 3CO → 2Fe + 3CO₂ Fe₂O₃ + 3C → 2Fe + 3CO
How is it formed?
it is cooled rapidly and solidified by running into sand moulds
What is silicon dioxide?
a non-metal, acidic oxide
Steps to the extraction of Al?
Bauxite is purified to produce Al₂O₃ Al.Oxide has a very high melting point - it is dissolved in molten cryolite to make an electrolyte which has a lower MP and is a better conductor of electricity At the cathode: Al³⁺ + 3e⁻ →Al Aluminium melts and collects at the bottom of the cell - then tapped off At the anode: 2O²⁻ →O₂ + 4e⁻ Some of the oxygen produced then reacts with the C of the electrode due to the HIGH TEMPS to produce CO₂ gas. Therefore the anode gradually burns away and needs to be replaced regularly.
What is done to solve this problem?
the aluminium oxide is dissolved in molten cryolite
What dictates the method of metal extraction?
position in RS
What are the issues with this?
Bound to be expensive -> the mroe reactive metal itself will have had to be extracted by an expensive process
What currents are used in the cell for the electrolysis of Al? WHAT BENEFIT DOES THIS HAVE?
very high the heat generated by the huge currents keeps the electrolyte molten so electrolysis remains constant BUT ELECTRICITY V.EXPENSIVE
Why does Al resist corrosion?
it has a very strong yet thin layer of aluminium oxide on the surface this prevents anything else from getting to the surface and reacting with it
What is the product called?
calcium silicate
Aluminium extractor diagram
Carbon anodes and cathodes Outer layer is a steel tank lined with heat resistant bricks The extractor is filled with a solution of Al₂O₃ in molten cryolite and the formed molten Al collects at the bottom
What is put into the BF?
iron ore, coke and limestone
What happens to the iron that is produced?
it melts and flows to the bottom of the furnace where it can be tapped off
What are the uses of Al?
ALLOYS OF Al: RESIST CORROSION LOW DENSITY STRONG CONDUCT ELEC/HEAT AEROPLANE BODIES - resists corrosion, low density and strong, high strength-to-weight ratio Pots and pans - shiny, resists corrosion, heat conductor Overhead power cables - resists corrosion, low density, electricity conductor Food cans - non toxic, resists corrosion
What is the first reaction?
strongly exothermic
How are metals above zinc extracted?
electrolysis - metal ions are reduced by being given ions at the CATHODE!
What are ores?
oxides compounds easily converted to oxides
Why is limestone added to the furnace?
to remove impurities in the ore which would clog the furnace with solid material
What is calcium oxide?
a basic oxide - reacts with acidic oxides/acids to form salts
What is a typical impurity that must be removed from the furnace?
silicon dioxide SiO₂
Why must you control how much limestone is put in the furnace?
the thermal decomposition of limestone that occurs is ENDOTHERMIC If too much then it will begin to cool the furnace
Why was the Bronze age before the Iron age?
Bronze = alloy of copper and tin Both metals are low in RS Easily made from ores by heating with C Iron h/e can also be made by heating with C but at v.high temps. More diffcult to purify into a useful form than copper in bronze - so became useful much later
What does this occur naturally as?
quartz
Section 2
(33 cards)