Extracting Metals Flashcards
Electrolysis definition
Breaking down of a substance using a direct current
What is oxidation ?
Loss of electrons
What is reduction?
Gain of elecrrons
What happens at the anode?
Positive cations are attracted and are reduced (gains electrons)
Creates a flow of charge through electrolyte to complete the
circuit
Product is then discharged from electrolyte
What happens at the anode?
Negative anions are attracted and are oxidised (lose electrons)
Creates a flow of charge through electrolyte to complete the circuit
Product is then discharged from electrolyte
Half equation of sodium at cathode
Na -> Na+ + e-
Half equation of hydrogen at anode
2H+ + 2e- -> H2
Product at cathode in aqueous solution
If hydrogen and metal ions are present, if metal is more reactive than hydrogen, hydrogen will be produced
Product at anode in aqueous solution
If hydroxide and halide ions were present, halogens would be formed. If no halide ions, oxygen would be formed
What happens to copper electrodes im electrolysis?
Copper anodes lose mass Cu(s) -> Cu2+ (aq) + 2e-
Copper cathodes gain mass (copper from anode) Cu2+ 2e- -> Cu(s)
What happens in electrolysis of impure copper?
Impure copper anode is oxidised, dissolving into electrolyte to form copper ions
Copper ions are reduced at pure copper cathode and forms pure copper layer
Any impurities from impure copper anode form a sludge at bottom of cell
Reactivity series mnemonic
Pop - Potassium (K) Stars - Sodium (Na) Can - Calcium (Ca) Make - Magnesium (Mg) Absolute - Aluminium (Al) Crazy - Carbon (C) Zillions - Zinc (Zn) If - Iron (Fe) Tiny - Tin (Sn) Little - Lead (Pb) Huge - Hydrogen (H) Children - Copper (Cu) Spend - Silver (Ag) Gold - Gold (Au) Pennies - Platinum (Pt)
Reactivity in comparison to oxidation
More reactivity = more likely to oxidise and more likely to become ion
Less reactivity = less likely to oxidise and less likely to become ion
Metal + water reaction
Metal + water -> metal hydroxide + hydrogen
Speed of reaction to reactivity
Higher reactivity = faster rate of reaction
How to choose metal extraction method
If more reactive than carbon, use electrolysis
If less reactive than carbon, heat with carbon unless inert
Ore definition
Rock contains enough metal to be economically worthwhile to extract metal from
Bioleaching method
Bacteria gets energy from bonds between atoms in ore, separating out metal from ore in process
Leachate (solution produced by process) contains metal ions which can be extracted using electrolysis or displacement
Phytoextraction method
Plant grows in soil rich in metal compounds
Plant can’t use metal compounds so it gradually builds up in the leaves
Plants are harvested, dried and burned in a furnace
Metal compounds in ash can be extracted using electrolysis or displacement
Recycling benefits
Doesn’t require combustion of fossil fuels (less energy, conserves finite resources e.g. metal) Cuts down on amount of rubbish sent to landfills Saves money (less energy used in extraction, reuses metals harder to extract / buy, creates jobs)
Life cycle
Choice of material
Manufacture
Product use
Disposal
Choice of material in life cycle facts
Metals have to be mined and extracted, using energy and creating pollution
Raw materials for chemical manufacture come from crude oil and is non-renewable, requires lot of energy, generates pollution
Manufacture in life cycle facts
Manufacturing uses energy and other resources
Creates pollution and waste which you need to dispose of safely
Chemical manufacture often needs water, and has a risk of polluting natural water sources
Product use in life cycle facts
Using products can damage environment e.g.
- paint gives off toxic fumes
- burning fuels releases greenhouse gases
- fertilisers can leech into streams and rivers, damaging ecosystems
