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5a: Extraction and uses of metals (uses of aluminium (Drinks/food can…
5a: Extraction and uses of metals
Reactivity
Electrolysis to extract metal from metal ore
Potassium - K
Sodium - Na
Lithium - Li
Calcium - Cu
Magnesium - Mg
Aluminium - Al
non-reactive, do not need extraction
Silver - Ag
Gold - Au
reduction using carbon
Copper - Cu
Zinc - Zn
Iron - Fe
(Hydrogen - H)
(Carbon - C)
Metals that are more reactive than carbon are extracted using electrolysis
Metals less reactive than carbon are extracted by reduction using carbon
Extracting Aluminium
Process
Aluminium oxide is dissolved in molten cryolite, this allows the temperature to be reduced to 9000
C (rather than 2000
C)
the carbon cathode lines the tank
there are many carbon anodes as the carbon reacts with the oxygen, at high temperatures and is converted to carbon dioxide
Problems
Anode - carbon wears away as it reacts with oxygen so it needs to be replaced
Energy Consumption - Aluminium oxide melts at 2000
C, the addition of cryolite means that the temperature is reduced to 9000
C, so less energy needed
Equation
Anode
Cathode
Extracting Iron
Coke
impure carbon needed for reducing Iron Oxide to Iron metal.
acts as a reducing agent
Process
1 - Hot air is blasted into the furnace, making the coke burn much faster than normal. This raises the temperature to about 1500*C.
2 - the coke burns and produces carbon dioxide
3 - the CO2 then reacts with unburnt coke to form CO
4 - the carbon Monoxide then reduces the iron ore to iron
5 - the iron is molten at this temperature and it's also very dense, so it runs straight to the bottom of the furnace where its tapped off.
Limestone
the main impurity is silicon dioxide (SiO2)
this is an acidic oxide
this is still solid at 1500*C and would stay mixed with the iron
the limestone removes it
1 - limestone is decomposed by the heat into calcium oxide and CO2
2 - the calcium oxide then reacts with the sand to form calcium silicate, or slag, which is molten and can be tapped off
3 - the cooled slag is solid and used for road building and Fertiliser
uses of aluminium
Drinks/food can
Resists corrosion
non toxic
overhead power cables
conducts electricity
source pans
good conductor of heat
Window frames
Resists corrosion
aeroplanes/bicycles
strong
Low density
Uses of Iron
Cutlery, cooking pans (as stainless steel)
Hard to break
can make alloys
cooking pans
good conductor of heat
high melting/boiling point
gates and railings
malleable
manhole covers
heard to break
car bodies
heard to break
high tensile strength
