Topic 4 – Extracting metals and equilibria Flashcards
oxidation
- gain of oxygen
- loss of electrons
reduction
- loss of oxygen
- gain of electrons
redox reaction
when both reduction and oxidation happen simultaneously.
One compound is reduced and the other is oxidised
displacement reaction
When a more reactive metal displaces a less reactive metal from its compound
what happens in a displacement reaction
- more reactive metal is oxidised : losing electrons. It becomes a cation
- less reactive metal ions are reduced : gaining electrons. it becomes an atom
- the positive metal ions bond with the negative ions to from the new compound, leaving the less reactive metal on its own
OIL RIG ( electrons )
Oxidation Is Lost
Reduction Is Gained
metals at top of reactivity series
- lose their electrons to form cations more easily
- gain oxygen more easily
metal + acid -> ?
salt + hydrogen
metals at bottom of reactivity series
- lose their electrons to form cations less easily
- gain oxygen less easily
how to test reactivity of metals
- see how quickly hydrogen is produced when you react metal with acid by attaching a gas syringe
- see how loud the squeaky pop sound is when you bring a lit splint near it
metal + water ->
metal hydroxide + hydrogen
reactions between metal and metal salt solutions
- see how many times the metal displaces another metal from its solution
- the metal with the most times is the most reactive
how do we extract metals such as gold
they are found in the crust as uncombined elements
metal ore
a rock that contains enough metal to make it profitable to extract metal from it
how are metals below carbon in reactivity series extracted from its ore? ( REDOX )
- reduced in a reaction with carbon
- because the carbon is more reactive it displaces the metal from its compound
- carbon is oxidised and metal reduced
how are metals above carbon in reactivity series extracted from its ore?
electrolysis
electrolysis of aluminium ( part 1 )
- purify bauxite ( ore ) and extract the aluminium oxide
- mix it with cryolite which lowers melting point - cheaper, saves energy
- melt it to form molten Al2O3 which is our electrolyte
electrolysis of aluminium ( part 2 )
- put molten Al2O3 in beaker and put 2 graphite electrodes in it.
- positive electrode which attracts anions + negative electrode which attracts cations
electrolysis of aluminium ( part 3 )
- the positive electrode attracts the negative oxygen ions and they react with carbon to form CO2
- the negative electrode attracts the positive Al3+ ions and they gain 3 electrons to form aluminium atoms and sink to bottom of beaker
disadvantages of electrolysis
- positive electrode must be replaced regularly
- vast amount of electricity required
- energy intensive
why do we use alternative methods of extraction?
- supply of some metal rich ores is running out
- this means we have to extract metals from low grade ores
- traditional methods are expensive and energy intensive
bioleaching
-bacteria mixed with low grade ore
- produces leachate which is soluble metal ore and contains higher concentration of metal ions
- these metal ions can be extracted through traditional methods
phytomining / phytoextraction
- plants grown on land containing metal compound
- metal compounds build up in leaves - plant harvested and burned in furnace
- ash contains high concentration of metal ions
advantages of alternative methods
- economical/ cheap
- much smaller environmental impact
- require less energy/ electricity
- don’t involve digging or transporting huge amounts of metal ores
disadvantages of alternative methods
- slower process
- metals in ground could harm plants in very high concentrations
sustainable development
- meets the needs of current generations without damaging lives of future generations
advantages of recycling -
- conserving energy and resources
- environmental benefits
- economic benefits
conserving energy and resources
- you use up less non renewables
- avoid burning fossil fuels which is very energy intensive
environmental benefits
- less mines dug
- ## less waste in landfill
economic benefits
- recycling metals can save money as metals are expensive to extract
- creates new jobs and improves economy
what 2 factors make metals more important to recycle
- more expensive to manufacture
- low quantity in earth’s crust
4 stages of Life cycle assessment
( R MUP )
- raw materials
- manufacturing and packaging
- usage
- disposal
alloy
mixture of 2 or more materials where at least 1 is a metal
why are pure metals more malleable? ( part 1 )
- regular arrangement of identical ions
- layers of ions can easily slide over each other, bending the metal
why are alloys stronger? ( part 2 )
- different elements have different sized atoms
- the smaller atoms will disrupt the regular arrangement of the bigger atoms
- this makes it MORE difficult for layers to slide over each other
steels
- iron that is alloyed with other elements
- makes iron stronger and less likely to rust
corrosion
when metals break down in the presence of oxygen and water to form their metal oxide
rusting
corrosion of iron
water, no oxygen
- nail is placed in water and a layer oil oil added on top to stop oxygen from entering
- no rusting
oxygen, no water
- nail placed in test tube and calcium chloride absorbs all water
- no rusting
water and oxygen
rusting
why is preventing corrosion so important?
structures such as metal bridges corrode over time and start to break down which makes it dangerous to walk on
creating a barrier
painting it
oiling or greasing
electroplating
sacrificial protection
placing more reactive metal with the metal
oxygen and water will react with the reactive metal instead
