❌C6.1 (3) - extractions Flashcards
c6.1.6 - extracting metals c6.1.7 - extracting iron c6.1.8 - extracting aluminium c6.1.9 - biological metal extraction
define an ore
a mineral or rock that contains a enough metal/metal compound to make it economical to extract the metal
(= the value of the metal is more than the cost of extracting it)
what is the ore to extract copper (carbonate)?
malechite
what is the ore to extract iron(III) (oxide)?
haematite
what is the ore to extract aluminium (oxide)?
bauxite
describe the 3 main stages to extract a metal
1) ore is mined
2) ore is processed
(metal compound separated from other substances in the ore)
3) metal is extracted from the pure method compound using chemical reactions
what is the mneunomic to remember the metal reactivity series?
(and what does each stand for - in terms of elements)
pink - potassium smiling - sodium cats - calcium meow - magnesium at - aluminium cute - carbon (NOT METAL) zebras - zinc in - iron the - tin long - lead hot - hydrogen (NOT METAL, USED FOR REFERENCE) curly - copper swirly - silver grass - gold privately - platinium
Please stop calling me a (cute) zebra, I think love has copper silver gold platinum
What extraction methods are there - when are they used
- in principle, all metals could be extracted from their compounds using electrolysis, but electricity is expensive
- if metal is less reactive than carbon, cheaper methods are used instead
- copper + iron are less reactive than carbon, so they can be extracted by heating their compounds with carbon or with carbon monoxide
all metals can be extracted from their compounds using …… but is expensive
electrolysis (electricity is expensive)
why can copper be extracted using carbon, but not sodium?
as copper is less reactive than carbon
- wheras sodium is too reactive to be extracted by reduction
describe the 2 main steps of how copper is extracted from copper sulfide
(and the word and symbol equation for each one)
1) copper sulfide (II) is ‘roasted’ in air
(to get it into metal oxide form for carbon to reduce later) :
copper(II) sulfide + oxygen -> copper(II) oxide + sulfur dioxide
2CuS(s) + 3O2 (g) -> 2CuO(s) + 2SO2 (g)
2) copper(II) oxide is heated with carbon:
copper (II) oxide + carbon -> copper + carbon dioxide
2CuO(s) + C(s) -> 2Cu(s) + CO (g)
2
explain how the extraction of copper sulfide is a redox reaction
- and what is the reducing agent
- copper(II) oxide loses oxygen and is reduced
- carbon gains oxygen and is oxidised
- carbon is acting as a reducing agent (reduced copper oxide to copper)
what form of carbon is used when extracting copper from copper sulfide?
charcoal
what is the machinery used to extract iron from its ore called?
a blast furnace
what are the raw materials used to extract iron?
and what is each one’s function
- iron ore (haematite - contains iron needed for extraction)
- coke (reduces iron(III) oxide to iron)
- limestone (purifies iron)
describe the three steps in which iron is extracted
- and the symbol equation for each one
1) coke burns in hot air, making carbon dioxide
C(s) + O (g) -> CO (g)
2 2
2) more coke reduces carbon dioxide to carbon monoxide
C(s) + CO (g) -> 2CO(g)
2
3) carbon monoxide reduces iron(III) oxide to iron
3CO(g) + Fe2O3(s) -> 3CO2 (g) + 2Fe (l)
what is the main reducing agent in the blast furnace for extracting iron from iron(III) oxide?
(and why can it do so)
carbon monoxide
- it is more reactive than iron
in what state does iron leave the blast furnace?
molten state (temperatures are very high, 1500C)
how is extracted iron purified?
- using limestone
1) calcium carbonate decomposes in the high temperatures :
CaCO3(s) -> CaO(s) + CO2(g)
2) calcium oxide reacts with silica from the sandy impurities from extracted iron to form calcium silicate:
CaO(s) + SiO2(g) -> CaSiO3(l)
The molten calcium silicate is called slag. It floats on the molten iron, and both the iron and slag are removed separately at the bottom of the blast furnace.
how does purified iron leave the blast furnace?
- as molten calcium silicate/slag floats on the molten iron (as it is less dense)
- iron leaves from bottom tube in liquid state
- slag leaves from tube on top of it
what does impure iron contain?
sandy impurities
why is the reaction between calcium oxide and silica a neutralization reaction?
as calcium oxide is slightly alkalinic
and silica is slightly acidic
how does a blast furnace work?
- raw materials added to top of blast furnace
(iron ore, such as haematite, which contains iron(III) oxide;
coke;
limestone, which is used to purify the iron ) - hot air forced in at the bottom of furnace = high temperature
- they react together at a high temperature
what is coke?
- a compound made of mostly carbon
- formed by heating coal in the absence of air
why is electrolysis used to extract some metals from their ores?
(and give an example)
if they are more reactive than carbon
ie. aluminum
why is aluminium oxide dissolved in molten cryolite?
- as electrolysis only works if the compound is in solution or molten (so ions can move)
- melting point of aluminium oxide is very high
- and aluminum oxide does not dissolve in water
- cryolite lowers melting point of aluminium oxide from 2000C to 950C
what is the structure which allows aluminium to be extracted from aluminium oxide?
(and what is it made of)
huge electrolysis cell
- carbon anodes
- carbon lining of cell (cathode)
- insulation on outside of cell
what is produced at the cathode and anode during electrolysis/extraction of aluminium?
(is it oxidation/reduction)
cathode (-) = aluminium ions are reduced (gain electrons)
anode (+) = oxygen ions are oxidised (lose electrons)
2 reasons why extraction of aluminium is expensive
- requires electricity (for electrolysis)
- carbon anodes constantly need replacing as oxygen reacts with carbon to produce carbon dioxide
how is aluminium oxide seperated?
- as in molten state, Al3+ ions and O2- ions are free to move around
- so aluminium is reduced by the carbon lining of cell and becomes molten aluminium
- as it is more dense than the aluminium oxide cryolite solution, it sinks
- and leaves the cell through the tapping hole (molten)
- oxygen ions are oxidised by the suspended carbon anodes
- and later react with the carbon and produce carbon dioxide
downside of extracting aluminium?
released carbon dioxide which is a greenhouse gas
write the half equations that happen at each electrode when aluminium oxide is extracted
cathode:
Al3+ + 3e- -> Al
anode:
2O 2- -> O2. + 4e-
what material lines the cathode and anode in the extraction of aluminium?
graphite
name 2 examples of alternative biological methods of metal extraction (and describe each one briefly)
bioleaching
- when bacteria breaks down low grade ores to metal compounds
- and produce leachate solutions with dissolved metal compounds
phytoextraction
- when plants absorb metal compounds from low-grade soil
- trapped within leaves/stem
- then burned to extract metals
how are the metals in bioleaching extracted?
metals are dissolved in solution, and dissolve in a stream/river
(collected at end)
why do bacteria cause the process of bioleaching to occur?
- similar to how we get energy from respiration
- bacteria get energy from breaking bonds
positives of bioleaching?
- energy efficient (compared to electrolysis)
- cheaper than traditional mining and processing
- no toxic greenhouse gases released
negatives of bioleaching?
- very slow
- toxic substances usually produced (must take care )
what allows metals to be extracted through phytoextraction?
- plant is burned
- ash contains a high concentration of metals
- which are extracted
what does a complexing agent do?
allows plants to absorb ions more easily (during phytoextraction)
positives of phytoextraction?
- cheaper than mining or processing
- less energy needed
- close to carbon neutral (carbon dioxide released when burning is absorbed when growing)
- allows a high concentration of metals to be extracted
negatives of phytoextraction?
- very slow
- reliant on the weather
- only certain plants absorb certain metal compounds
what is good about phytoextraction and bioleaching?
both can extract metals from low-grade ores (which would have been unviable)
- and some ores are becoming scarce
What does the method chosen to extract a metal depend upon
Its position in the reactivity series
Extracting metals topic:
Copper(II) oxide can also be reduced to copper by heating it with __ or with __
Rather than carbon
Methane, hydrogen
Extracting iron topic:
Iron is extracted from a large reaction container called what?
Blast furnace
Why is limestone added to blast furnace - in a sentence
Limestone - used to purity the iron
