1. Electrolysis

2. –A redox reaction that is made to occur by passing a direct electric current through an electrolyte Electrolyte –is a liquid that conducts electricity. –contains ions that are free to move and –either a molten ionic compound or an aqueous solution of an ionic salt.

3. Electrodes are immersed in the electrolyte and connected to the DC power supply –The negative electrode is called the cathode and the positive electrode is called the anode. Cation is positive ion Anion is the negative ion The electrodes are often inert –e.g. graphite or platinum, and are not involved in the electrolysis reaction itself.

4. Electrolytic cell Both Electrolyte and electrodes When it is working: Reaction only occurs at the surface of the electrodes cations move towards the cathode and are reduced anions migrate to the anode and are oxidised.

5. Molten Sodium Chloride cathode reaction: Na + (l) + 1e   Na(s) anode reaction: 2Cl  (l)  Cl 2 (g) + 2e  Overall balanced equation for the cell reaction: 2Cl  (l) + 2Na + (l)  Cl 2 (g) + 2Na(s) D.C Cathode Anode Na + Cl -

7. Aqueous Copper Sulphate D.C Cathode Anode Cu (s) Solid Copper on Cathode O 2(g) Oxygen Gas released at Anode Cathode Anode Cu (s) Solid Copper on Cathode Cl 2(g) Chlorine Gas released at Anode D.C Aqueous Copper Chloride Cu 2+ Cl - Cu 2+ H + SO 4 2- O 2- H 2 SO 4

8. Important Industrial Process 1 The electrolytic extraction of Al from alumina, Al 2 O 3, originally found in the ore bauxite which is mined in Northern Queensland. The electrolysis occurs at Tiwai Point, Southland. Reactions occurring during electrolysis are: Cathode:Al 3+ + 3e   Al(reduction) Anode:2O 2   O 2 + 4e  (oxidation) The carbon anodes that are used (as metal electrodes would alloy with the molten aluminium that is produced) have to be replaced periodically because they react with the oxygen produced to form carbon dioxide

9. Important Industrial Process 2 The electrolytic extraction of magnesium from sea water. The seawater is first concentrated by evaporation during which most of the sodium chloride present precipitates out. Solid magnesium chloride is obtained by precipitation with hydroxide followed by reaction with hydrochloric acid. Reactions occurring during electrolysis are: Cathode:Mg 2+ + 2e   Mg (reduction) Anode:2Cl   Cl 2 + 2e  (oxidation)

10. Chem 2.7 Exam Questions may involve any of the following: the properties of common oxidants and reductants, and the products of their reaction.the properties of common oxidants and reductants, and the products of their reaction. Common oxidants are limited to: O2, I2, Cl2, Fe3+, H2O2, MnO4  (aq)/H+, Cr2O72  (aq)/H+Common oxidants are limited to: O2, I2, Cl2, Fe3+, H2O2, MnO4  (aq)/H+, Cr2O72  (aq)/H+ Common reductants are limited to: metals, C, CO, H2, Fe2+, Br , I , SO2, (HSO3  ).Common reductants are limited to: metals, C, CO, H2, Fe2+, Br , I , SO2, (HSO3  ). Properties are limited to appearance (colour and state), oxidation numberProperties are limited to appearance (colour and state), oxidation number writing balanced oxidation–reduction equationswriting balanced oxidation–reduction equations classifying balanced half-equations as oxidation or reductionclassifying balanced half-equations as oxidation or reduction identifying the oxidant and/or reductant from a given reactionidentifying the oxidant and/or reductant from a given reaction principles of simple electrolytic cells.principles of simple electrolytic cells.