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Electrolysis - Coggle Diagram
Electrolysis
Metal Ore Extraction
Metals can be extracted from their ores using electrolysis if the metal is too reactive to be reduced with carbon or if it reacts with carbon.
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Example:
-Aluminium is extracted from the ore Bauxite using electrolysis
-Bauxite contains Al₂O₃
-Since the meting point of aluminium oxide is very high it's mixed with cryolite to lower the melting point
-The molten mixture has free ions so can conduct electricity
-The positive Al³⁺ ions pick up three electrons at the cathode and turn into aluminium atoms and sink to the bottom of the tank.
-The negative O²⁻ lose two electrons at the anode and combine to form O₂ molecules
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Aqueous solutions
In aqueous solutions, as well as the ions from the ionic compound there are also hydrogen ions ( H⁺) and hydroxide ions ( OH⁻)
Cathode: If the metal ions will produce a metal that is LESS reactive than Hydrogen then the metal will for. If the metal ions will form a metal that is MORE reactive than hydrogen then hydrogen will form
Anode: If halide ions are present then the halogen will form. Otherwise the hydroxide ions are discharged and oxygen will form
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- During electrolysis a current is passed through the electrolyte.
- The ions move towards the electrodes
- The ions react at the electrodes
- The compound decomposes
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Molten Ionic Compounds:
- Can be electrolysed because ions can move freely and conduct electricity
- Molten ionic compounds are always broken up into their elements
- Metal cations are reduced to the element at the cathode
- Non-metal anions are oxidised at the anode.