Topic 4 - Extracting Metals and Equilibrium Flashcards
reactivity series of metals
Potassium, sodium, calcium, magnesium, aluminium, zinc, iron, tin, lead, copper, silver, gold, platinum
The more reactive a metal is… (2)
The more vigorous its reactions and the more easily it forms cations
Potassium and sodium reaction with water
Violent with cold water
Calcium, magnesium reaction with water
Slow with cold water, rapid with steam
Aluminium and zinc reaction with water
Usually no reaction
Iron reaction with water
Rusts slowly
Copper, silver and gold reaction with water
None
Potassium and sodium reaction with acid
Violent
Calcium, magnesium, aluminium reaction with acid
Rapid
Zinc and iron reaction with acid
Slow
Copper, silver and gold reaction with acid
None
Metal + water..
Metal hydroxide and hydrogen
Metal + steam…
Metal oxide and hydrogen
Metal and acid..
Salt and hydrogen
Which metals dont react with acid?
Those below hydrogen in the reactivity series
Metal displacement reactions
A more reactive metal can displace a less reactive metal from a compound, are REDOX reactions
Ore definition
A rock that contains enough of a metal or metal compound to make extracting the metal worthwhile
Low grade ore vs high grade ore
Low - small percentage of metal or compound
Extraction with carbon (3)
Only works with metals less reactive than carbon
What does it mean if metals are found in their native state?
Very unreactive elements (gold, silver, platinum) found as uncombined elemnts
Metals electrolysed to purify (5)
Potassium, sodium, calcium, magnesium, aluminium
Metal oxides heated with carbon to purify (3)
Zinc, iron, copper
Native state elements (2)
Silver, gold
Haematite
Iron oxide ore
Malachite
Copper carbonate containing ore
Disadvantages of electrolysis (2)
- requires a lot of energy to melt metal
Bioleaching (4)
- Bacteria grown on low grade ore
Metals extracted using bioleaching (4)
Nickel, cobalt, zinc, copper
Phytoextraction
Growing plants that absorb metal compounds. The plants are then burnt to form ash from which metal is extracted.
Advantages bioleaching (4)
- conserves supplies high grade ore
Disadvantages bioleaching (2)
- very slow
advantages of phytoextraction (4)
- can extract metals from contaminated soils
Disadvantages phytoextraction (2)
- more expensive than mining
Bauxite
A mineral used in making aluminum
Why is aluminium more expensive than iron if it is more abundant?
Takes more energy in extraction process
Why is aluminium oxide mixed with cryolite when extracting aluminium?
To lower the melting point of the aluminium oxide, so less energy needed to melt it (aluminium oxide insoluble in water so can’t be aqueous)
Why must the anodes used in aluminium extraction be replaced?
Oxygen reacts with carbon anodes, forming CO2
Steps to recycle a metal (3)
1) collect and transport used items to a recycling centre
Advantages of recycling metals (3)
more economical - less energy is needed to recycle than produce a metal.
Disadvantages of recycling (2)
labor intensive
Life Cycle Assessment
Analysis of environmental impacts of products from the design stage through end-of-life.
Stages of LCA (4)
- Obtaining raw materials
Raw materials (2)
- uses up limited resources eg crude oil
Manufacture (2)
- uses land for factories
Use
Depends on how much maintenance a product needs, and how durable it is
Disposal (2)
Using up land for landfill sites
What chemical reactions are reversible?
All! (In principle)
reversible reaction
a chemical reaction in which the products re-form the original reactants
Decomposition of ammonium chloride
NH4CL(s) ⇌ NH3(g)+HCl(g)
Dynamic equilibrium
Position attained in a reversible reaction when the net concentration of reactants and products stay the same
What does ‘dynamic’ mean in dynamic equilibrium?
The forward and backwards reactions continue to occur at the same rate
What prevents equilibrium being obtained?
If it does not take place in a closed system, and reactants or products can escape
Haber process
N2(g) + 3H2(g)⇌2NH3(g)
Haber process steps (5)
- Nitrogen (extracted from the air) and hydrogen (obtained from natural gas) are pumped through pipes.
Molecules of gas are directly proportional to…
Gas pressure
How does gas pressure change equilibrium
If pressure is increased, equilibrium position moves in the direction of fewer molecules of gas as the system attempts to decrease gas pressure
How does concentration affect equilibrium?
If concentration of a reactant increases, the equilibrium position moves in the direction with less of the reactant
How does temperature affect equilibrium
If the temperature is increased, the equilibrium moves in the direction of the endothermic process as the system uses up the extra heat energy
In every reversible equation, one is endothermic and one is…
Exothermic
