05. Electricity and Chemistry

• Define electrolysis as the breakdown of an ionic compound, molten or in aqueous solution, by the passage of electricity

• Describe the electrode products and the observations made during the electrolysis of:

–– molten lead(II) bromide

–– concentrated hydrochloric acid

–– concentrated aqueous sodium chloride

–– dilute sulfuric acid

between inert electrodes (platinum or carbon)

• State the general principle that metals or hydrogen are formed at the negative electrode (cathode), and that non-metals (other than hydrogen) are formed at the positive electrode (anode)

• Predict the products of the electrolysis of a specified binary compound in the molten

state

• Describe the electroplating of metals

• Outline the uses of electroplating

• Describe the reasons for the use of copper and (steel-cored) aluminium in cables, and why plastics and ceramics are used as insulators

• Relate the products of electrolysis to the electrolyte and electrodes used, exemplified by the specific examples in the Core together with aqueous copper(II) sulfate using carbon electrodes and using copper electrodes (as used in the refining of copper)

• Describe electrolysis in terms of the ions present and reactions at the electrodes in the examples given

• Predict the products of electrolysis of a specified halide in dilute or concentrated aqueous solution

• Construct ionic half-equations for reactions at the cathode

• Describe the transfer of charge during electrolysis to include:

–– the movement of electrons in the metallic conductor

–– the removal or addition of electrons from the external circuit at the electrodes

–– the movement of ions in the electrolyte

• Describe the production of electrical energy from simple cells, i.e. two electrodes in an electrolyte. (This should be linked with the reactivity series in section 10.2 and redox in

section 7.4.)

• Describe, in outline, the manufacture of:

–– aluminium from pure aluminium oxide in molten cryolite (refer to section 10.3)

–– chlorine, hydrogen and sodium hydroxide from concentrated aqueous sodium chloride

(Starting materials and essential conditions should be given but not technical details or

diagrams.)