Chem T3 - Predicting products of electrolysis

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  • Predicting products of electrolysis
    • In molten ionic solids only 1 source ions
      • 1. Ionic solid can't be electrolysed as ions are in fixed positions & can't move.
      • 2.) Molten ionic compounds can be electrolysed as ions can move freely & conduct electricity
      • 3.) Positive metal ions are reduced to metal atoms at cathode
      • 4.) Negative ions oxidised to atoms or molecules at anode
      • 5.) e.g. PbBr? see brown vapour of bromine gas at anode, silver coloured liquid at cathode as molten lead is formed
    • Electrolysis Aqueous solutions (more complicated)
      • 1.) In aqueous solutions aswell as ions from ionic compound, hydrogen ions (H ) & hydroxide ions (OH ) present from water
      • Cathode reaction rules: Always hydrogen H? discharges unless aqueous metal ion less reactive then hydrogen
      • Anode reaction rules: Always oxygen O? unless anion (negative ion) from dissolved compound is chloride bromide or iodide (halide ions)


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