Extraction And Uses Of Metals Maud Flashcards
When is the method of heating the ore with carbon or carbon monoxide used?
When a metal is less reactive than zinc
What is electrolysis used for
Extracting metals that are more reactive than zinc
The name of aluminium’s ore?
Bauxite
What is bauxite
Impure aluminium oxide
Equation for aluminium ions being reduced to aluminium?
Al 3+ + 3e- –> Al
Equation for oxygen ions forming oxygen gas?
2O 2- –> O2 + 4 e-
How does bauxite become aluminium and oxygen?
The aluminium ions are attracted to the cathode and are reduced to aluminium
Oxygen ions are attracted to the anode and lose electrons to form oxygen gas
What is aluminium oxide dissolved in and why?
It is dissolved in an aluminium compound called cryolite as a flux to lower its melting point
Melting aluminium oxide requires extremely high temperatures
Why do the anodes have to be replaced regularly?
Because of the high temperatures, the carbon anodes will burn with the oxygen produced to form carbon dioxide.
What currents do the cells have?
What does this mean?
Currents up to 100 000
This means it is expensive
Why is aluminium good for making aircraft with?
Resists corrosion due to its aluminium oxide coat
Has low density
Strong
Why is aluminium good for making saucepans with?
Keeps its shiny appearance
Good conductor of heat
Resists corrosion
Low density
Why does aluminium resist corrosion?
Because of its tenacious oxide layer
What method is used to extract aluminium?
Electrolysis
What method is used to extract iron?
The blast furnace
What is the name of irons ore?
Haematite
What is haematite?
An ore that contains iron (III) oxide
What is coke and what is it used for?
Coke is impure carbon that burns to form carbon dioxide
It is used to heat the blast furnace as burning it is a strongly exothermic reaction.
Blast furnace
Carbon to CO2?
C + O2 –> CO2
At high temperatures, what happens to the carbon dioxide formed by coke?
Equation?
The carbon dioxide is reduced by more carbon to give carbon monoxide
C + CO2 –> 2CO
What does carbon monoxide do in the blast furnace?
Equation?
It is the main reducing agent
Fe2O3 + 3CO –> 2Fe + 3CO2
What is the other reducing agent other than carbon monoxide?
Reaction?
Carbon
Fe2O3 + 3C –> 2Fe + 3CO
What happens to the limestone in the furnace?
Equation?
The heat of the furnace causes the limestone to thermally decompose form calcium oxide and carbon dioxide
CaCO3 –> CaO + CO2
What happens to the calcium oxide in the blast furnace?
The calcium oxide reacts with acidic silicon dioxide(sand). SiO2 is one of the impurities found in haematite.
Molten calcium silicate is formed and trickles to the bottom of the furnace as molten slag
SiO2 + CaO –> CaSiO3(slag)
What goes in at the top of the blast furnace?
Iron ore, coke and limestone
What comes out at the top of the blast furnace?
Hot waste gases
What is the blast furnace made from?
Steel lines with heat resistant brick
What are electrolysis tanks made from?
Steel lined with refractory brick
What is the temperature range in the blast furnace?
400-1800 degrees
What goes in at the bottom of the blast furnace?
Hot air is blasted in
What comes out at the bottom of the blast furnace?
Molten slag and below that molten (iron)
Types of iron?
Wrought iron Mild steel High-carbon steel Cast iron Stainless steel
Wrought iron (what mixed with, properties and uses?)
Pure iron
Very soft
Decorative work such as gates and railings
Mild steel (what mixed with, properties and uses?)
0.25% carbon
Tough, malleable
Nails, car bodies and ship building
High-carbon steel (what mixed with, properties and uses?)
0.25 - 1.5% carbon
Hard
Cutting tools
Cast iron (what mixed with, properties and uses?)
About 4% carbon
Very brittle but strong
Manhole covers
Guttering
Engine blocks
Stainless steel (what mixed with, properties and uses?)
Chromium and nickel
Resists rusting
Expensive
Cutlery
Cooking utensils
Ways of preventing the rusting of iron?
Using barriers
Alloying the iron
Using sacrificial anodes
Using barriers to prevent the rusting of iron?
Keep water / oxygen away from the iron by painting / coating it with oil e.t.c
Alloying the iron to prevent it rusting?
Such as allowing it with chromium and nickel to produce stainless steel
Using sacrificial anodes to prevent iron rusting?
Galvanising iron by coating it with a layer of zinc
Zinc is more reactive than Iron and will corrode instead
During the process it loses electrons to form ions
These electrons flow into the iron so any iron atom which has lost electrons immediately regains them
These mean that even if the zinc is scratched, the iron won’t rust
