C6.1 Extracting metals Flashcards
What is an ore?
Metal compound which is mined then the metal is extracted
What is below hydrogen in the reactivity series, in order?
Copper
Silver
Gold
Platinum
What is the copper carbonate ore?
Malachite
What is the aluminium oxide ore?
Bauxite
What is the iron oxide ore?
Haematite
Method for extracting aluminium?
Electrolysis
Why is electrolysis expensive?
Energy/ electricity for the current ( anode , cathode) and energy to melt ore so it is molten / in solution
How can Iron be extracted?
Reduction - adding carbon to displace the metal from its oxide
Explain step by step of iron extraction?
Hot air (oxygen) reacts with the coke (carbon) to produce carbon dioxide
More coke is added to the furnace and reduces the carbon dioxide into carbon monoxide.
iron(III) oxide is reduced.
Once molten iron is formed, what does it contain which needs to be removed
Sandy impurities
How are sandy impurities removed?
Using limestone, calcium carbonate decomposes, the calcium oxide formed reacts with silica from sandy impurities to form calcium silicate
What is calcium silicate called?
slag
Why do metals have high melting points?
Strong metallic bonds
Why is cryolite used to melt aluminium?
It would be very expensive otherwise
How does cryolite work with aluminium?
Aluminium oxide is dissolved in cryolite. Cryolite has a lower melting point so uses less energy
Where does aluminium go?
To the cathode, around the edge
Where does the oxygen go?
Anode, to the top bits
What does the oxygen react with at the anode?
Carbon to form carbon dioxide
What is cryolite?
A aluminium compound
Why does aluminium oxide need to be molten?
So the ions become charged and move
What is the half equation at the anode?
2O^2- = O2 + 4e-
What is the half equation at the cathode?
Al3+ + 3e- = Al
Why does the anode need to be replaced regularly?
It is made out of carbon (graphite) and reacts with the oxygen
What is electrolysis?
the breakdown of compounds into ions using electricity
Where are most metals found?
In the earths crust, already reacted with with elements like oxygen
What does economical mean?
Cost effective
What is a low grade ore?
Contain only a small amount of a metal
Is it harder or easier to extract copper economically from low grade ores?
Harder
Explain bioleaching?
Bacteria is mixed with a low grade ore. The bacteria can break down low grade ore to produce acidic solution containing copper ions also known as a leachate.
What is Leachate?
An acidic solution which contains the metal compound we want
Positives (3) of bioleaching?
POS- cheaper than traditional ways, simple, cheap and allows metal to be extracted from ores that contain too little metal for it to be profitable
Negatives (4) of bioleaching?
NEG - Slow process as plants need to grow, toxic chemicals are released, low efficiency for bacteria to convert copper ore into copper metal. A lot of waste is produces
Why are phytoextraction and bioleaching good economically and sustainably?
Both allow economically extraction of metals from low grade ores. This is important as there is a limited supply of earths resources
After bioleaching and phytoextraction, what do you have?
A metal compound
What do you need to do after bioleaching and phytoextraction?
Process the metal compound. Iron is more reactive than copper so scrap iron is also cheaper than copper so can displace the copper from the Leachate. Cost effective way to produce copper from leachate
OR the leachate can be electrolysed
Positives of Phytoextraction? 3
Cheaper than traditional techniques, contributes to sustainable development, produces less waste
Negatives of phytoextraction?
Very slow as plant needs to grow, crops may need replanting and maintenance
