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COMMERCIAL ELECTROLYTIC CELLS (MOLTEN ELECTROLYTES (electrodes = inert,…
COMMERCIAL ELECTROLYTIC CELLS
MOLTEN ELECTROLYTES
electrodes = inert
anode = conductive material = graphite/platinum
cathode = iron = inert b/c electrons pumped onto electrode = can't react
Cathode (-) : Na+ (l) + e- --> Na (l)
Anode (+): 2Cl- (l) --> Cl2 (g) + 2e-
no water present to interfere with reactions
molten = more energy required
iron mesh = keeps products at anode/ cathode apart
AQUEOUS ELECTROLYTES (membrane cell)
e.g. concentrated sodium chloride solution (brine)
2 compartments separated by semipermeable membrane
prevents contact b/w reactive products
membrane ONLY allows positive ions through
NaOH solution isn't contaminated with NaCl solution
aqueous electrolyte occurs at 80-90oC = lower cost = no need to heat
ELECTROLYTIC PRODUCTION OF ALUMINIUM
aluminium obtained from aluminium oxide (alumina - Al2O3)
alumina = soluble in molten cryolite (Na3AlF6)
dissolving alumina in cryolite lowers temp. electrolysis performed at
Cathode (-): Al3+ (in cryolite) + 3e- --> Al (l)
Anode (+): 2O2- (in cryolite) --> O2 (g) + 4e-
oxide ions react w/ carbon anode = CO2 (g) C (s) + 2O2- (in cryolite) --> CO2 (g) + 4e-
