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Predicting the products after the electrolysis of aqueous solutions.
Rule 1: Identify the cations and anions in the electrolyte. Remember that an aqueous solution also contains H+ and OH- ions from the dissociation of water molecules.
Rule 2: At the anode, the product of electrolysis is always oxygen unless the electrolyte contains a high concentration of the anions, Cl-, Br- or I- ions.
Rule 3: At the cathode, reactive metals such as sodium and potassium are never produced during electrolysis of the aqeous solution. If the cations come from a metal above hydrogen in the reactivity series, then hydrogen will be liberated. If the cations come from a metal below hydrogen, then the metal itself will be deposited.
Rule 4: Identify the cations and anions that remain in the solution after electrolysis. They form the product remaining in solution. Summarise the reactions.