Topic 3 revision: Electrolytic Processes

What is electrolysis? Breaking down an ionic substance using electricity. Metals have a positive charge and non metals have a negative charge. Hydrogen is an exception (it is a non metal with a positive charge.

Anode Cathode = bromide ion = lead ion

What happens at the electrodes? Use the electrolysis of lead bromide as an example. The ions discharge and elements re-form. So, at the anode bromine forms and at the cathode lead forms.

Ionic half equations Electrolysis of CuCl2 Anode: 2Cl-  Cl2 + 2e- Cathode: Cu2+ + 2e-  Cu Electrolyse these: CaF2 AlBr3

Electrolyus 2H+ + 2e-  H2 2Cl-  Cl2 + 2e- Na+ and OH- are left behind to create NaOH in the solution. Only the least reactive element will form at the electrode. This is not needed but you may wish to share this with G+T.

At the anode anode anode e- Cu Cu2+ e- Cu Cu2+ Cu  Cu2+ + 2e-

At the cathode Cu2+ + 2e-  Cu cathode Cu2+ cathode cathode e- Cu e- Pure Copper Cu2+ + 2e-  Cu

What about the impurities anode anode As the anode dissolves The impurities are released They sink to the bottom As anode slime Pt Ag Au Valuable stuff Anode Slime

Refining copper At the positive anode Copper atoms lose electrons and become copper ions. The positive ions drift away from the anode Cu  Cu2+ + 2e- The anode dissolves At the negative cathode Positive copper ions drift to the cathode. They gain electrons and become copper atoms Cu2+ + 2e-  Cu The cathode is electroplated

Electroplating Two uses: To galvanise metals (to stop corrosion) To make things more attractive.