Extraction Flashcards
(29 cards)
Extraction
-process of obtaining a metal from a mineral, usually by reduction or electrolysis
What does the extraction method usually depend on?
-the metal’s position in the reactivity series
Why do we need an ionic compound to be in a liquid state rather than solid during electrolysis?
-the ions need to be free to move
- so when an electrical current is passed through the electrolyte solution, the ions move and separate towards the electrodes
How can we produce molten copper from copper oxide?
-heat it with carbon
-2CuO(s) + C(s) > 2Cu (l) +CO2 (g)
-copper oxide is reduced while carbon is oxidised, redox reaction
What extraction method would you use for metals above carbon in the reactivity series?
-electrolysis of molten compounds
What extraction method would you use for metals below carbon in the reactivity series?
-redox reaction by heating with carbon
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Why might we need to do chemical reactions to get an unreactive metal, despite it being found as the metal itself?
-to remove other elements that might contaminate it
How can we produce molten iron from iron (III) oxide?
-react it with carbon
- iron(III) oxide + carbon → iron + carbon monoxide
-Fe2O3(s) + 3C(s) → 2Fe(l) + 3CO(g)
How does the extraction method of heating by carbon work, if carbon is the more reactive element?
-carbon is more reactive so it can displace the metal from its metal compound
-so carbon becomes oxidised while the other metal is reduced (redox reaction)
How come when you heat copper oxide with carbon, carbon dioxide is produced, but when you heat carbon with iron oxide carbon monoxide is produced?
-copper oxide is easily reduced by carbon at moderate temperatures in plentiful oxygen
-carbon fully oxidises to carbon dioxide
-iron oxide requires higher temperatures and different conditions (blast furnace), where less oxygen is present
-carbon monoxide is produced
In the reaction of iron(III) oxide with carbon, state which substance is reduced and which substance is oxidised
-iron oxide is reduced, loses oxygen
-carbon is oxidised, gains oxygen
Why might someone prefer to extract a metal by heating with carbon than with electrolysis?
-it is cheaper
Why is aluminium more expensive than iron, despite it being more abundant?
-large amounts of electrical energy used in the extraction process
Electrolyte
-substance which, when molten or
dissolved in a solution, will conduct an electric current
Cathode
-negative electrode, where metal ions gain electrons and form atoms
Anode
-positive electrode, where oxide ions lose electrons and form oxygen gas
Electrolysis method:
- put two electrodes (anode and cathode) into an electrolyte
- attach electrodes to a power supply
- Positive ions move toward the cathode (-), while negative ions move toward the anode (+)
- at cathode, ions gain electrons (reduction)
at anode, ions lose electrons
To which electrode are cations (positive ions) attracted to?
-cathode (negative electrode)
To which electrode are anions (negative ions) attracted to?
-anode (positive electrode)
Explain, with the help of a half equation, how aluminium ions are
reduced during the electrolysis of aluminium oxide
-half equation is: Al3+ + 3e- → Al
-shows that aluminium ions gain electrons, and reduction is gain of electrons
Phytomining definition
-using plants to absorb metal compounds from the soil as part of metal extraction
Phytomining method (copper)
-plants are grown in soil that contains low grade ore
-plants absorb copper ions through their roots and concentrate these ions in their cells
-burn the plants to create ash that contains copper oxide as the copper reacts with oxygen from the air while burning
-react ash with sulphuric acid to make copper sulphate
-electrolyse it
Advantages of phytomining
-less energy required than smelting
-reduces rock waste
-uses low grade copper ore
-produces less air pollution
