Topic 4 - Extracting metals and equilibria Flashcards
How does phytoextraction work?
- Plants grown in areas with metals in soil.
- The plant takes up metals through their roots and concentrate them in their shoots and leaves.
- These plants are burned and metals are removed from the ash
What is oxidation in terms of oxygen?
Gain of oxygen
What are advantages of recycling metals?
- Economically beneficial as electrolysis is expensive
- Prevents harmful environmental impact of mining and extraction of new metals
- Less waste produced so less landfill
- Less energy required compared to electrolysis
- More sustainable - not using up finite resources
- Recycling process provides employment
Where are most metals extracted from?
The Earth’s crust
A metal reacts with oxygen but not acid or cold water, what does this suggest about the reactivity of the metal
It isn’t very reactive, most metals react with oxygen
How can aliminium be extracted from its ore?
Aliminium is more reactive than carbon so electrolysis must be used, metal forms at cathode
When aliminium is extracted from aliminium oxide, why is it first dissolved in molten cryolite?
Aliminium oxide has very high melting point. It is dissolved in molten cryolite to produce electrolyte with lower melting point reducing energy usage and cost
Fill in the gap: ‘The reactivity of a metal is related to its tendency to form _______’
The reactivity of a metal is related to its tendency to form
cations
What are limitations of biological methods of extraction?
- Only suitable for low grade ores with smaller quantities of metals
- Slow process
- Require displacement or electrolysis for final step
What is an ore?
A rock which contains metals often chemically combined with other substances
How is a metal’s relative resistance to oxidation is related to its position in the reactivity series
Oxidation is loss of electrons. metals lower in reactivity series are less reactive meaning they are less likely to form their cations so are more resistant to oxidation (gain of oxygen)
What is a life cycle assessment?
Analysis of overall environmental impact a product may have throughout its lifetime
What is the reactivity series
What is the reactivity series
What are alternative biological methods of extraction?
- Phytoextraction
- Bacterial extraction
How does bacterial extraction work?
- Some bacteria absorb metal compounds
- These bacteria produce solutions called leachates containing the metals
- Scrap iron can be used to remove metal from leachate
Which metals are found in the earth’s crust as uncombined elements?
Unreactive metals
What process is carried out to extract metals?
Reduction of ores
What is chemical equation for reduction of iron with carbon?
2Fe2O3 + 3C –> 4Fe + 3CO2
How can metals be extracted from ores and what cases is each one done
- Heating with carbon (reduction): Can only be done if metal is less reactive than carbon
- Electrolysis: Can be done with all metals but requires large amount of energy and has high cost
What does it suggest about a metal’s reactivity if a metal reacts with cold water
Metal is very reactive as only most reactive metals can react with cold water
Why can a displacement reaction be called a redox reaction?
- A redox reaction occurs when reduction and oxidation are taking place in the same reaction
- In a displacement reactoin, the more reactive metal atoms lose electrons to form ions (oxidation) and the less reactive metal ions gain electrons to form the element (reduction)
What factors affect life cycle assessment?
- Obtaining the raw materials (extraction and processing)
- Manufacturing the product
- Use of product
- Disposal of the product when it is no longer useful
How would you extract iron from its ore?
Iron is less reactive than carbon so heating with carbon. (Electrolysis could be used but would use a lot of unnecessary energy and have a high cost
What is reduction in terms of oxygen?
Loss of oxygen
