The process of electrolysis
When an ionic compound is melted or dissolved in water , its ions are
free to move . The liquid or solution conducts electricity and is
called an electrolyte
Passing a current through the electrolyte makes the ions move to the
electrodes :
Positive ions (cations) go to the negative electrode , the
cathode Negative ions (anions) go to the positive electrode , the
anode
At the electrodes the ions are discharged : they lose their charge
and become elements . This whole process is electrolysis
The electrodes are inert (graphite or platinum) so they do not
react
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An electrolysis cell electrolyte — the ionic compound molten or dissolved, so the ions are free to move d.c. supply − + cathode (−) anode (+) attracts positive ions attracts negative ions + − + − + − positive ions move to the cathode, gain electrons and are reduced (PIC — positive ions to the cathode) negative ions move to the anode, lose electrons and are oxidised The electrodes are usually inert graphite. A solid ionic compound will not work — the ions are held in a lattice and cannot move, so it must be molten or dissolved in water first. An electrolysis cell: power supply, two graphite electrodes labelled anode (+) and cathode (−) dipping into an electrolyte, with positive ions drawn moving to the cathode and negative ions to the anode
The rest of this topic is in the full Exam Guide The complete AQA GCSE Chemistry guide — every topic, exam checklist and common mistake — is coming soon. Until then, the first topic in every unit is free to read.
In the full topic
• The process of electrolysis• Electrolysis of molten ionic compounds• Extracting aluminiumRead the free chemistry topics →