Extracting and using metals
Only the most unreactive metals such as gold
and platinum are found as native metals.
All the other metals we use are extracted
from their ores by chemical processes.
iron ore
ores
native
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igcse-extraction-and-uses-of-metals.pdf, Lecture notes of Chemical Processes
Extracting and using metals. Only the most unreactive metals such as gold and platinum are found as native metals. All the other metals we use are extracted.
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2021/2022
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Extracting and using metals^ Only the most unreactive metals such as goldand platinum are found as
native metals
All the other metals we use are extractedfrom their
ores
by chemical processes. iron ore
ores native
Definition:
An^ ore
is a rock containing enough of a metal compound for it to be worth extracting the metal from the rock.
The metal compounds in rocks are often metal oxides,sometimes metal sulphides or carbonates. Bauxite
contains aluminium oxide, from which we extract aluminium. Galena
is lead sulphide from which we obtain lead. Iron pyrites
(Fools Gold) is actually iron sulphide, and
contains no gold. We normally obtain iron from an orecalled
haematite
which contains iron oxide.
Extraction and uses of Iron Reduction is used to extract ironfrom its ore (haematite) which ismainly iron(III) oxide.The iron ions are reduced to ironatoms, using carbon. This is oxidisedto form carbon dioxide. iron(III) oxide + carbon
iron + carbon dioxide
2 Fe
O^2 3(s)
- 3C
(s)^
^
4 Fe
- 3 CO(l)^
2(g)
The process happens in a
blast
furnace
Raw materials: Iron ore
- contains the iron to be extracted Coke - contains the carbon to reduce the iron ore Air^ – provides oxygen to burn thecarbon, which also heats the blastfurnace Limestone - is mainly calcium carbonate, which removes theimpurities (sand) in the iron ore byreacting to form slag, which floats onthe molten iron
What comes out: Molten iron
- this is cast iron and
contains carbon impurities. It is brittleand not yet very useful. Slag
- calcium silicate is a waste product, but can be used for roadsurfacing. Carbon dioxide - produced in several
of the reactions in the blast furnace. Nitrogen
- left over from the air going into the blast furnace, after theoxygen has been used in reactions.
The uses of iron arise from its properties. Cast iron can be alloyed to make itsproperties more suitable for specific purposes.Different types of steels are alloys of iron,each with different properties.
Stainless
steel
has added chromium atoms and resists corrosion, remaining shiny.
Mild steel
is iron with up to 0.3% carbon. It is hard and strong, but not brittle, soit can be shaped e.g. for car body panels,ship building etc.
High-carbon steels
have up to 2% carbon.
They are very hard – useful for knife blades,but are brittle so cannot be bent to shape.
The lead oxide is then heated with coke (carbon) in a blast furnace to cause a displacement reaction
which produces lead and carbon dioxide. This works
because carbon is more reactive than lead, so carbon can
reduce
the lead oxide
to lead.
2PbO
- C(s)^
(s)^
^
2Pb
- CO(l)^
2(g)
Extraction and Uses ofAluminium Electrolysis is used to extractaluminium from aluminium oxide;this is obtained by purifying its ore(bauxite). The ionic aluminium oxide is splitinto its elements, aluminium (ametal) and oxygen (a gas). aluminium oxide
aluminium + oxygen
2 Al
O^2 3(l)
4 Al
(l)^
- 3 O
2(g)
The uses of aluminium arise from its properties. Pure aluminium istoo soft to be much use. It can be alloyed to make their propertiesmore suitable for specific purposes.
alloy
pure metal
Harder: layersdisrupted, can’tslide over eachother
Soft: layers canslide over eachother
By growing the oxide layer on the surface of titanium todifferent thicknesses, it can be made to reflect differentcolours of light.
Extracting titanium from rutile^ Carbon can’t be used to extracttitanium from its ore because thetitanium reacts further with carbon,so a more reactive metal, e.g.
sodium
or^ magnesium
, is used to reduce
the titanium ore instead.
For both titanium and aluminium: Extraction of these metals from their ores is expensive.- because there are many stages in the processes- large amounts of energy are needed
rutile – titanium ore
Aluminium alloys are used for commercial aircraft• light weight (low density)• good strength• corrosion resistance