Topic 4- Extracting metals and equilibria Flashcards
Explain displacement reactions as redox reactions
- More reactive metals form a cation (+) as they displace the less reactive metal losing electrons and being oxidised– forms an ion as it replaces less reactive metal in salt solution
- Less reactive metals form atoms from negative ions as they’re displaced, gaining electrons and being reduced
- forms atom as it’s replaced in salt solution
Reactivity series of metals with water and dilute acid ?
- metals react with other substances, metal atoms form positive ions
- Reactivity of a metal is related to its tendency to form positive ions– more reactive metals form positive ions more easily
- Metals arranged in order of reactivity in reactivity series
Where are metals found?
- most metals extracted from ores found in Earth’s
crust, unreactive metals found in Earth’s crust as
uncombined elements - &, most metals found as compounds that require chemical reactions to extract the metal
How to extract metals less reactive than carbon?
- extracted from oxides by reduction w/ carbon
- reduction involves loss of oxygen, so ores reduced to remove the oxygen to obtain the pure metal
Method used to extract metal from its ore
- Can only be extracted by reduction of carbon if metal is less reactive so carbon can displace metal from ore
- If more reactive than carbon, use electrolysis, but electrolysis can be expensive, since requires a lot of energy
How to extract metal using carbon? e.g. Iron
- Iron oxide loses oxygen, and is reduced– carbon gains oxygen, and is oxidised.
- For iron, this is carried out at high temperatures in a blast furnace
How to extract metal via electrolysis e.g. aluminium
- Metals more reactive than carbon e.g aluminium are extracted by electrolysis of molten compounds.
- uses molten mixture of aluminium oxide and carbon as the electrodes
- aluminium has positive charge, so it forms at cathode and oxygen has a negative charge so it forms at anode
Describe Phytoextraction:
○ Some plants absorb metal compounds through their roots
○ concentrate these compounds into their shoots and leaves
○ plants burned to produce an ash that contains the metal
compounds
Describe bacterial extraction
- Some bacteria absorb metal compounds
○ Produce solutions called leachates which contain them
○ use scrap iron to obtain the metal from the leachate
how is a metals’ resistance to oxidation related to its
position in the reactivity series
- less reactive a metal is, the more resistant it is to oxidation, since to react metal forms a positive metal ion by losing electrons
Advantages of recycling metals
-Requires less energy to melt and remould metals than to extract new metals from their ores
- Mining ores is bad for the environment –quarries created, produce noise pollution and dust
- allows waste metals to be reused, saving money,
helping the environment and the supply of valuable raw materials
What is the life assessment of a product?
- stages carried out to assess environmental impact of products
Stages of a life time assessment
Extracting and processing raw materials
- Manufacturing and packaging
- Use and operation during its lifetime
- Disposal at end of its useful life, including transport and distribution at each stage
What is a reversible reaction?
- a chemical reactions, where products of the reaction can react to produce the original reactants
e. g. Haber process nitrogen + hydrogen ⇌ ammonia
Difference between equilibrium and dynamic equilibrium
equilibrium
-rate of forward reaction = rate of backward reaction
- concentration of reacting substances stay the same
dynamic equilibrium
- once forward and backward reaction reach equilibrium, they keep going
