Extracting Metals Flashcards
What is an ore?
A metal ore is a rock which contains enough metal to make it worthwhile extracting the metal from it
What is the ore in many cases?
The oxide of the metal
How do most ores need to be extracted?
Using chemical reactions
How can economics affect metal extraction?
If the market price of a metal drops a lot it might not be worth extracting it
As technology improves it becomes possible to extract more metal making it worth it
What two ways can a metal be extracted from its ore chemically?
Reduction
Electrolysis
If an ore is concentrated, what does that mean?
The unwanted Rocky material is removed
What else can electrolysis to used to do?
Purify the extracted metal
What does reduction mean?
Using carbon- The removal of oxygen
Often requires electrolysis after to purify the metal
What determines whether a metal can be extracted by reduction?
It’s position in the reactivity series
Which metals can / can’t be extracted by reduction?
Metals below carbon can
Metals above carbon can’t
This is because carbon can only take the oxygen away from metals which are less reactive than itself
How are metals more reactive than carbon extracted?
Extracted using Electrolysis of molten compounds
Why is electrolysis much more expensive than reduction?
It used a lot more energy due to the high temperature used to melt the oxide so it can be extracted
How is copper extracted?
Copper can be extracted by reduction with carbon
The ore is then heated in a furnace (smelting)
The copper produced is impure and doesn’t conduct electricity very well
Electrolysis is used to purify it
Define electrolysis?
The breaking down of a substance using electricity
What is the liquid required to conduct the electricity in electrolysis known as?
The electrolyte
What are the electrolytes often?
Metal salt solutions made from the ore
Or molten metal oxides
What does the electrolyte have allowing the process to work?
Free ions
Where are electrons taken from / given too?
Taken away by the positive anode and given away by the negative cathode, as ions gain or lose electrons they become atoms or molecules and are released
Describe how electrolysis is used to get copper?
1) electrons are pulled off copper the atoms at the anode cashing them to go into solution as Cu2+ ions
2) Cu2+ ions near the cathode gain electrons and turn back into copper atoms
3) the impurities are dropped at the anode as a sludge whilst pure copper atoms bond at the cathode
Why do more reactive metals react more vigorously than less reactive metals?
If you put a reactive metal into a solution of a dissolved metal compound the reactive metal will replace the less reactive metal in the compound (displacement)
Why does displacement happen?
The more reactive metal bonds more strongly to the non metal part of the compound (pushes out the less reactive metal)
Why is it useful that scrap iron can be used to displace copper and what’s the equation for this?
Iron is much cheaper than copper
Copper sulfate + iron —> Iron sulfate + copper
Why Is it important to recycle as much copper as possible?
The supply of copper rich ores is limited and the demand for copper is growing which may lead to shortages in the future
What are two ways of extracting copper from low grade ores or from the waste of copper extraction?
Bioleaching
Phytomining
What is bioleaching?
This uses bacteria to separate copper from copper sulfide
The bacteria get energy from the bond between copper and sulfur separating out the copper from the ore in the process
The leachate (solution produced) contains copper which can be extracted by filtering
What is phytomining?
This involved growing plants in soil that contain copper
The plants absorb copper and can’t use or get rid of the copper so it gradually builds up in the leaves
The plants are then harvested , dried and burned in a furnace
The copper can be collected from the ash left in the furnace
Copper extracted from solution made by ash using electrolysis
Pure copper is produced
What is a positive and negative of extraction by bioleaching and phytomining?
Positive- they have a much smaller impact on the environment than traditional methods
Extracts from low grade ores
Doesn’t damage landscape
Negative- these processes are much slower
Produces smaller amount of copper
Produces carbon dioxide when plants burn
Why is mining metal ores good?
Useful products are made
Provided locals with jobs and boosts economy so services such as health can be improved
Why is mining ores bad?
It’s bad for the environment
Causes noise and visual pollution
Loss of habitats
Deep mine shafts can be dangerous for a long time after the mine has been abandoned
Why is recycling metals important?
Mining and extracting metals takes a lot of energy which comes from burning fossil fuels which are running out and contribute to acid rain, global dimming and climate change
How much energy does recycling use?
Only a small fraction of the energy needed to extract new metals
(Copper = 15% energy of extracting new)
Energy is expensive so recycling saves money
What two other reasons is recycling metals important?
There’s a finite amount of metals on earth recycling conserves this
recycling metal cuts down rubbish going into landfill which takes up space and pollutes surroundings
Describe mining and smelting?
Copper mined from earth
Copper ore heated in furnace with carbon (smelting and reduction)
Produces impure copper
Copper purified by electrolysis
Pure copper produced
What is an advantage and disadvantage of mining, smelting and reduction?
Advantage = quickest and extracts more copper so more economic
Disadvantage= supply Of copper rich ores is limited Noise Destruction of habitats Smelting uses non renewable fuel and produces carbon dioxide adding to global warming
