C6 Electrolysis
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What happens to the ions in an ionic compound when it is melted or dissolved
• They are free to move • And carry a charge
What is an electrolyte
• A liquid or aqueous • ionic compound
What happens to ions during electrolysis
• ions are attracted to electrodes of the opposite charge • negative ions are attracted to the anode • they loose electrons there • positive ions are attracted to the cathode • where they gain electrons
Electrolysis of molten compounds
• positive ions are attracted to the cathode- gain electrons and form metals • negative ions are attracted to the anode • loose electrons and form non-metals
why is electrolysis used to extract metals
• as they are too reactive • to be reduced by carbon
Why is lots of energy needed during electrolysis
• Melt the compound • produce electrical current
Why is cryolite added when electrolysising aluminium
• cryolite is added to lower the melting point of alumium • so less energy is needed
Why must the anode be replaced during the extraction of aluminium
• The electrode is made of carbon • The carbon reacts with the oxygen • to form carbon dioxide
What are ions are present with electrolysising in solution
• H+ • OH- • Metal + • Non metal -
What forms at the cathode (aq)
• Cathode = negative • If metal is less reactive than hydrogen then it is formed • copper • platinium • silver • gold • If it is more reactive hydrogen is formed
What is produced at the anode (aq)
• Anode = Positive • If halide (group 7 ion) is present –> it forms • If not oxygen forms • 4OH-(aq) –> O2 (g) + 2H2O(l) + 4e-
half equations
• Make sure that the charge is the same on both sides • OILRIG