Extraction And Uses Of Metals Flashcards
Infinite or finite number of metal ores?
They are know as “finite resources”
How does the reactivity series help us with extracting metals?
The more reactive a metal is, harder it is to extract it from a compound
What is the reaction called that separates pure metal from their oxides?
The reaction the separates a metal from the oxygen in its oxide is called a reduction reaction
What is reduction? Example
Loss of oxygen
E.G. Copper oxide + carbon —> copper + oxygen
What is the substance that is oxidised called in a reduction reaction?
The reducing agent as is reduced to its ‘normal’ form
How is a reduction reaction done with carbon?
A less reactive metal ore is heated with carbon monoxide
What makes a metal compound a metal ore?
If it has enough metal in it that it is pronounced worth extracting
How do you extract aluminium?
By using electrolysis
What is the symbol for pure aluminium oxide?
Al O
2 3
What is aluminium a main ore?
Bauxite
Why don’t we melt bauxite?
It has a very high boiling point at over 2000°C as it would be very expensive
What is aluminium oxide dissolved in to bring the boiling point down?
Cryolite ( a less common ore of aluminium ) this brings the boiling point down to around 900°C which makes it easier to melt
Why is electrolysis expensive?
- Requires a lot of electricity and energy to heat the mixture = expensive
- The disappearing positive electrode needs frequent replacement
What is the equation for the decomposition of of aluminium oxide?
Aluminium oxide —> aluminium + oxygen
What is the negative electrode known as?
Cathode
What is the positive electrode known as?
Anode
Why does the molten aluminium conduct electricity?
Because it contains free ions which can transport electricity
What happens to the positive aluminium ions?
They are attracted to the negative electrode called the cathode where they pick up electrons and turn into aluminium atoms then they sink to the bottom
What happens to the negative oxygen ions during electrolysis?
They are attracted to the positive electrode called the anode where they lose electrons. The oxygen atoms react together to form O2 or with the carbon anode as well to form to CO2
Why does the anode or the positive electrode often need replacing?
Because it is constantly reacting with oxygen and so gets worn down
What is the symbol equation for what is happening at the cathode?
Al 3+ + 3e - —> Al
What is the symbol equation for what is happening at the anode?
2O 2- —> O + 4e -
2
Where is iron extracted from? What is its symbol?
Iron is extracted from its ore called haematite
Fe O
2 3
How is iron extracted from its ore?
By reduction (removal of oxygen) in a blast furnace
What are the ingredients that are put into a blast furnace and what do they do?
Iron ore - contains iron
Coke (almost pure carbon) - reducing the iron oxide to iron metal
Limestone - takes away impurities in the form of slag
What is the first step in extracting iron from and iron ore using a blast furnace?
Hot air is blasted into the furnace, making the Coke burn much faster than normal, raising the temperature inside the furnace to about 1500°C
What is the second step in extracting iron from and iron ore using a blast furnace? What is the symbol equation?
Coke burns and produces carbon dioxide
Carbon + oxygen —> carbon dioxide
C + O —> CO
2 2
What is the third step in extracting iron from and iron ore using a blast furnace? What is the symbol equation?
The carbon dioxide reacts with the u burnt coke to form carbon monoxide.
Carbon dioxide + carbon —> carbon monoxide
CO + C —> 2CO
2
What is the forth step in extracting iron from and iron ore using a blast furnace? What is the symbol equation?
The carbon monoxide then reduces the iron ore to iron
Carbon monoxide + iron (III) oxide —> carbon dioxide + iron
3CO + Fe O —> 3CO + 2Fe
2 3 2
What is the final step in extracting iron from and iron ore using a blast furnace?
The iron is molten at this temperature and also is very dense. As such it falls straight to the bottom of the furnace and is tapped off there
What is the main impurity and what removes it?
Sand (silicon dioxide) is the main impurity and it is removed by limestone
How does the limestone remove the sand?
The limestone is decomposed by the heat into calcium oxide and CO(2)
CaCO —> CaO + CO
3 2
The calcium oxide reacts with the sand to form calcium silicate or slag which is molten can be tapped off
CaO + SiO —> CaSiO
2 3
What can the slag be used for?
The cooled slag is solid and can be used for roadbuilding or for fertiliser
What properties do iron and aluminium share?
- Both metals
- Both dense and shiny
- Both have high melting points
- Both have high tensile strength (strong and hard to break)
- Both malleable (hammered into shape)
- Both good conductors of heat energy and electricity
What is wrought iron, and what is it used for?
It is completely pure iron that is malleable and often used for ornamental gates and railings
What are two examples of iron alloys?
Cast iron
Steel
What is cast iron and what is it used for?
It is iron with a mixture of carbon and silicon. It is very hard but brittle.
It is often used for manhole covers and some cooking pans
What is steel and what is it used for?
Steel is an alloy made up of iron, carbon and usually some other metals.
It is harder than pure iron but can be hammered and made easily into sheets and welded together.
These properties mean steel is great making carbodies and girders (for construction)
Why is cutlery made out of stainless steel?
Because pure iron rusts very easily. Stainless steel is an alloy made from iron and chromium and it does not rust.
What is the main way that aluminium different from iron?
Aluminium does not corrode easily
Why is it useful that aluminium does not corrode?
Because it means that it can be used for products where liquid is involved and will not rust such as with fizzy drink cans
Why is aluminium particularly useful for aeroplanes and bicycle frames?
Because aluminium is a lot less dense than iron meaning that it is quite light. It is used for aeroplanes because of this
Talk about aluminium and aluminium oxide. How is it useful?
Aluminium react very quickly with oxygen in the air to form aluminium oxide.
A nice protective layer of aluminium oxide sticks firmly to the aluminium below and stops any further reaction taking place.
