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4.3 Electrolysis - Coggle Diagram
4.3 Electrolysis
Extracting metals
Anode continually replaced
Anode made of carbon which reacts with oxygen to produce carbon dioxide
Aluminium oxide and cryolite
Cryolite lowers melting temperature
Requires lots of energy
Used if...
The metal recats with carbon
The metal is more reactive than carbon
Use the reactivity series to determine type of extraction
Half equations
E.g.
2Br- → Br2 + 2e- Pb2+ + 2e- → Pb
Balance the electrons to combine half equations
Show reduction reactions at the cathode, oxidation reactions at the anode
The process
Splitting up with electricity
Electric current passes through the electrolyte, ions move towards the electrodes where they react
Electrolyte
Molten or aqueous ionic compound
Conducts electricity
Electrodes
Conducts electricity
Solid placed in the electrolyte
Anode
Negative ions move towards the anode
Positive electrode
Cathode
Positive ions move towards the cathode
Negative electrode
To remember electrode charge:
P
ositive
A
node
N
egative
I
s
C
athode
Ionic compounds
Must be molten or aqueous so the ions are free to move
Aqueous solutions
At the cathode, hydrogen is produced if the metal is more reactive than hydrogen
At the anode, oxygen is produced unless the solution contains halide ions - then the halogen is produced
Molten compounds
The metal is produced at the cathode
Non metal produced at the anode
Lead bromide example
Lead produced at
cathode, bromine produced at anode