electrlysis Flashcards
charge of the cathode
negative
charge of the anode
positive
What happens at the anode?
Non-metal ions are oxidised to the element at the anode.
What happens at the cathode?
Metal ions are reduced to the element at the cathode.
What does a solution need to be to be electrolysed?
A molten ionic compound. An ionic solid cannot be electrolysed as the ions are in fixed position and cannot move.
Why would electrolysis need to be used?
If a metal is too reactive to be reduced with carbon or reacts with carbon then electrolysis can be used to extract the metal.
Disadvantage of electroylsis.
Expensive lots of energy is needed to melt the compound and pass current through.
What other ions form in aqueous solutions.
OH- and H+
How do you determine what is produced at the cathode in the electrolysis of an aqueous solution?
If the metal that the ions form are more reactive than hydrogen, then hydrogen gas is produced. If the metal is less reactive than hydrogen a solid layer of pure metal is produced instead.
How do you determine what is produced at the anode in the electrolysis of an aqueous solution?
If OH- and halide ions are present, molecules of chlorine, bromine or iodine will be formed. If no halide ions are present then OH- ions are discharged and oxygen will be formed.
Half equation for OH- ions
4OH- -> O2 + 2H2O + 4e-
