describe the electrolyte and write the anode and cathode half reactions Solution

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the negative electrode (-) is called the cathode and attracts positive ions or cations e.g. Al3+, and the positive electrode (+) is called the anode and attracts negative ions or anions e.g. O2-. At the negative (-) cathode, reduction occurs (electron gain) when the positive aluminium ions are attracted to it. They gain three electrons to change to neutral Al atoms. Al3+ + 3e- ==> Al At the positive (+) anode, oxidation takes place (electron loss) when the negative oxide ions are attracted to it. They lose two electrons forming neutral oxygen molecules. 2O2- ==> O2 + 4e- or 2O2- - 4e- ==> O2 Note: Reduction and Oxidation always go together! The overall electrolytic decomposition is ... aluminium oxide => aluminium + oxygen 2Al2O3 ==> 4Al + 3O2 and is a very endothermic process, lots of electrical energy input! Note that the aluminium oxide loses its oxygen, therefore in this electrolytic process the compound aluminium oxide is reduced to the metal aluminium.

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