contents
• Electrolysis of molten
compounds
• Electrolysis of solutions
• Electroplating
• Extraction of metals
• Electric cells
electrolysis of molten compounds
 an electrolyte is an ionic compound that conducts
electricity; molten state or solution in water
 molten ionic compounds and solutions of ionic compounds
can conduct electricity due to presence of mobile ions that
can carry current
 electrolysis is the conduction of electricity by an electrolyte,
leading to its decomposition
 example: electrolysis of molten sodium chloride
 inert electrodes (e.g. carbon electrodes) do not react in
electrolysis
electrolysis of molten compounds
electrolysis of molten sodium chloride
battery
-
+
carbon anode; attracts
anions; oxidation
carbon cathode; attracts
cations; reduction
molten sodium
chloride
porcelain crucible
pipeclay triangle
HEAT
STRONGLY
tripod
ammeter to
show current
flowing
electrolysis of molten compounds
electrolysis of molten sodium chloride
 molten sodium chloride contains Na+ and Cl- ions
 at the cathode, Na+ ions take in electrons to become Na
atoms; Na+ ions are discharged
Na+(l) + e
Na(l)
 at the anode, Cl- ions give away electrons to become Cl2;
Cl- ions are discharged
2Cl-(l)
Cl2(g) + 2e-
 overall reaction
2NaCl(l)
2Na(l) + Cl2(g)
electrolysis of molten compounds
electrolysis of molten sodium chloride
electrons flow
from battery
into cathode
sodium metal
produced
electrons flow
from anode
into battery
molecules of
chlorine gas
produced
sodium atom
sodium ion
attracted to cathode
sodium ion
takes electron
from cathode
chlorine atom
chloride ion
gives electron
to anode
chloride ion
attracted to anode
cathode
anode
electrolysis of molten compounds
electrolysis of other molten compounds
 when a molten ionic compound is electrolysed, metal is
produced at the cathode; non-metal is produced at the
anode
Molten Electrolyte
Product at
Cathode
Product at Anode
calcium chloride, CaCl2
calcium, Ca
chlorine, Cl2
sodium iodide, NaI
sodium, Na
iodine, I2
lead(II) oxide, PbO
lead, Pb
oxygen, O2