C6 Electrolysis Flashcards
why can solid ionic compounds not conduct electricity?
the ions are locked in place and are not free to move
why can liquid or dissolved ionic compounds conduct electricity?
the forces of attraction between molecules are broken so the ions are free to move
what is an electrolyte?
a molten or dissolved ionic compound which can conduct electricity
what are the electrodes in electrolysis made from?
a conducting material e.g. graphite
or a metal
what is the negative electrode called?
the cathode
it is covered with electrons from the power pack
what is the positive electrode called?
the anode
it has a lack of electrons
what happens to positive ions in electrolysis?
they are attracted to the cathode.
they gain electrons and become atoms
this is a reduction reaction
what happens to negative ions in electrolysis?
they are attracted to the anode
they lose electrons to form atoms
this is an oxidation reaction
which metals are extracted with electrolysis?
ones more reactive than carbon
what is aluminium extracted from and how?
aluminium oxide
electrolysis
what is aluminium oxide mixed with during electrolysis and why?
cryolite
this lowers the melting point of aluminium oxide which reduced the amount of energy needed and saves money
what is the half equation for the electrolysis of aluminium oxide at the cathode?
Al3+ + 3e- –> Al
this is a reduction reaction
what is the half equation for the electrolysis of aluminium oxide at the anode?
2O2- –> 2O + 4e-
OR
2O2- - 4e- –> 2O
this is an oxidation reaction
why does the anode have to be replaced reguarly?
the oxygen molecules produced at the anode react with the graphite (carbon), forming CO2
why is electrolysis expensive?
melting the compound requires lots of energy
a lot of energy is required to produce the electric current
