Electrolysis of Molten Ionic Compounds (GCSE Chemistry)
Electrolysis of Molten Ionic Compounds
Electrodes and Half Equations
- Electrodes can be inert. Inert electrodes are sometimes used in electrolysis. The electrodes are called ‘inert’ because they are unreactive. We can use inert electrodes in the electrolysis of molten lead (II) bromide.
- Carbon is used as an inert substance. The inert electrodes can be made of carbon. This is good, because carbon won’t react with the electrolyte and it also has a high melting point.
- There are rules to half equations. For molten ionic substances, there are some rules to writing half equations. In general, the metal is produced at the cathode. The non-metal is produced at the anode.
- Half equations can be written. As we’ve seen previously, we can use half equations to demonstrate the process of electrolysis.
Lead Bromide
- At the cathode, lead is formed. This appears as the silvery liquid metal underneath the remaining electrolyte.
Pb2+ + 2e–→ Pb
- At the anode, bromine is formed. This appears as bubbles of brown gas.
2Br– – 2e– → Br2
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Zinc Chloride
- At the cathode, zinc is formed. This appears as metal underneath the remaining electrolyte.
Zn2+ + 2e– → Zn
- At the anode, chlorine is formed. This appears as bubbles of gas.
2Cl– – 2e– → Cl2
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