Electrolysis Flashcards
Cation
positive metal ion
Anion
Negative ion
positive ions are attracted to…
the negative electrode (-)
Negative ions are attracted to….
Positive electrode (+)
Electrolyte
Molten or aqueous solution in which ions are free to move
Why can’t solid ionic compounds conduct?
Ions are fixed and cannot move
Oxidation
Loss of electrons
Reduction
Gain of electrons
Molten electrolysis rules
positive metal ions –> negative electrode
Negative non-metal ions
–> positive electrode
Ionisation of water in aq electrolysis
H2O –> H+ + OH-
Aqueous electrolysis rules
(positive ions)
Less reactive element is produced.
Collect hydrogen unless Cu, Ag, Au, Pt
Aqueous electrolysis rules
(negative ions)
Halogen or Oxygen. Halogen takes priority.
Half equation for the formation of oxygen gas from discharged hydoxide ions
4OH- -4e –> O2 + 2H2O
Products when molten lead(II)bromide is electrolysed
Lead @ negative electrode
Bromine @ positive electrode
Why is a mixture of aluminium oxide and cryolite used as the electrolyte in the extraction of aluminium?
The mixture has a lower melting point. Saves some energy and therefore reduces costs.
Why do the carbon anodes have to be replaced regularly in the extraction of aluminium?
The oxygen produced at the positive anode reacts with the hot carbon anodes, producing carbon dioxide.
What is electrolysis?
The breakdown of a substance using electricity.
Where does oxidation happen in electrolysis?
Positive electrode
Where does reduction happen in electrolysis?
Negative electrode
What 3 products do you get when you electrolyse aqueous sodium chloride?
Hydrogen, Chlorine and sodium hydroxide.
Explain why metal in wires conducts electrolysis
delocalised sea of electrons, free to move
For the extraction of aluminium, write the half equation at the positive electrode
2O2- –> O2 + 4e-
