Electrolysis of Molten Ionic Compounds (AQA GCSE Chemistry: Combined Science)
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Chemistry Lead
Electrolysis of Simple Ionic Compounds
- Lead(II) bromide is a binary ionic compound meaning that it is a compound consisting of just two elements joined together by ionic bonding
- When these compounds are heated beyond their melting point, they become molten and can conduct electricity as their ions can move freely and carry the charge
- These compounds undergo electrolysis and always produce their corresponding element
- To predict the products of any binary molten compound first identify the ions present
- The positive ion will migrate towards the cathode and the negative ion will migrate towards the anode
- Therefore the cathode product will always be the metal and the product formed at the anode will always be the non-metal
Diagram showing the electrolysis of lead (II) bromide
Method:
- Add lead(II) bromide into a crucible and heat so it will turn molten, allowing ions to be free to move and conduct an electric charge
- Add two graphite rods as the electrodes and connect this to a power pack or battery
- Turn on the power pack or battery and allow electrolysis to take place
- Negative bromide ions move to the positive electrode (anode) and lose two electrons to form bromine molecules. There is bubbling at the anode as brown bromine gas is given off
- Positive lead ions move to the negative electrode (cathode) and gain electrons to form grey lead metal which deposits on the bottom of the electrode
Electrode Products:
Anode: Bromine gas
Cathode: Lead metal
Exam Tip
Remember electrodes need to be inert such as graphite or platinum so that they don’t participate in a side reaction with the electrolyte.
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