Extraction and use of metals Flashcards
the more reactive a metal is…
the harder it is to extract it from a compound
lots of common metals react with…to form…
oxygen…oxides
what is the reaction that involves the separation of a metal from the oxygen?
a reduction reaction
what is the reducing agent?
the substance that reduces the metal
what is the most common reducing agent?
carbon
copper oxide is reduced to copper:
2CuO + C = 2Cu + CO2
Methods of extraction are linked to the…
order of reactivity
only metals…than…can be reduced by…
less reactive…carbon…carbon
very reactive metals form…
very stable ores
metals that are more reactive than carbon need to be extracted using…
electrolysis
what is the melting point of aluminium?
2000 degrees celcius
what is aluminium dissolved in?
molten cryolite (a less common ore than aluminium)
What does the molten cryolite do?
it brings the temperature down to about 900 degrees celcius
what electrode are the aluminium ions attracted to?
the negative
what happens to the aluminium atoms once they gain electrons?
they sink to the bottom
why do the positive electrodes always need to be replaced?
they get worn down by reacting with oxygen
at the negative electrode:
Al3+ + 3e- –> Al
at the positive electrode:
202- –> O2 + 4e-
why is electrolysis expensive?
- it uses lots of electricity
- the need to heat the electrolyte
- the frequent replacement of electrodes
what are the raw materials used for extracting iron from iron ore?
- iron ore
- coke
- limestone
what is coke?
almost pure carbon
what is the purpose of limestone?
to take away impurities in the form of slag
step 1:
hot air is blasted into the furnace, making the coke burn much faster than normal
this raises the temperature to about 1500 degrees Celsius
Step 2:
the coke burns to produce carbon dioxide
step 2 equation:
C + O2 –> CO2
step 3:
the carbon dioxide then reacts with the unburnt coke to form carbon monoxide
step 3 equation:
CO2 + C –> 2CO
Step 4:
the carbon monoxide then reduces the iron ore to iron
step 4 equation:
3CO + Fe2O3 –> 3CO2 + 2Fe
step 5:
the iron is molten at this temperature but is also very dense, so it runs straight to the bottom of the furnace where it’s tapped off
What is the main impurity from this process?
sand (silicon dioxide)
what removes the impurity?
the limestone
Step 1 of removing the impurity:
the limestone is decomposed by the heat into calcium oxide and carbon dioxide
Step 1 of removing the impurity: equation
CaCO3 –> CaO + CO2
Step 2 of removing the impurity:
the calcium oxide reacts with the sand to form calcium silicate, or slag, which is molten and can be tapped off
What is the cooled slag used for?
- road building
- fertiliser
what are the properties of aluminium and iron? (6)
- both dense and lustrous (shiny)
- high melting points
- high tensile strength
- malleable
- good conductors of electricity
- good conductors of heat energy
uses of iron:
- wrought iron (malleable)
- alloys
what is cast iron made of?
iron, carbon and silicon
what is steel made of?
iron, carbon and usually some other metals
what is the main problem with iron?
it corrodes easily
uses of aluminium:
- it doesnt corrode so is used for products that come into contact with water (eg drinks cans)
- aluminium is much less dense than iron so can be used for bicycle frames and aeroplanes
What is ammonia used for?
Fertilisers
Making nitric acid
Making nylon
Where does the nitrogen come from?
Air
Where does the hydrogen come from?
Natural gas
What temperature does the Haber process happen at?
450
What pressure does the haber process happen at?
200 atm
What is the catalyst used for the Haber process?
Iron
First step contact process
Majing sulfur dioxide
Second step contact process
Making sulfur trioxide
Third step contact process
Making liquid oleum
Fourth step contact process
Making concentrated sulfuric acid
Uses for sulfuric acid
Fertilisers
Detergents
Paints
Temperature contact process
450
Pressure contact process
2 atm
Catalyst contact process
Vanadium(v) oxide
