Electrolytic ProcessesEdexcel GCSE Chemistry: Flashcards

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Define an electrolyte.

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Define an electrolyte.: An ionic compound in the molten state or dissolved in water that can conduct electricity.
Define electrolysis.: The decomposition of an electrolyte using electrical energy from a d.c. supply.
Which electrode do cations move towards?: The cathode (negatively charged electrode).
Which electrode do anions move towards?: The anode (positively charged electrode).
What forms at the cathode when electrolysing sodium chloride solution with inert electrodes?: Hydrogen.
What forms at the anode when electrolysing sodium chloride solution with inert electrodes?: Chlorine.
What products form when molten lead bromide is electrolysed?: Lead at the cathode, bromine at the anode.
What is the rule for what forms at the cathode with an aqueous solution and inert electrodes?: Hydrogen forms, unless the metal ion is less reactive than hydrogen, in which case the metal forms.
What is the rule for what forms at the anode with an aqueous solution and inert electrodes?: Oxygen forms, unless a halide ion is present, in which case the halogen forms.
Define oxidation and reduction in terms of electrons.: Oxidation is the loss of electrons; reduction is the gain of electrons.
Which electrode process is reduction and which is oxidation in electrolysis?: Reduction occurs at the cathode; oxidation occurs at the anode.
Write the half equation for copper ions being reduced at the cathode.: Cu2+ + 2e− → Cu
Write the half equation for chloride ions being oxidised at the anode.: 2Cl− → Cl2 + 2e−
What happens at the copper anode during purification of copper by electrolysis?: Copper atoms lose electrons and dissolve into solution as Cu2+ ions, so the anode gets smaller.
What happens at the cathode during purification of copper by electrolysis?: Cu2+ ions gain electrons and are deposited as pure copper, so the cathode gets bigger.