7. Metallurgy
(i) Occurrence of metals in nature: Mineral and ore - Meaning and definition. Common ores of iron, aluminium and zinc.
(ii) Stages involved in the extraction of metals.
- (a) Pulverization and dressing of the ore β hydrolytic method, magnetic separation, froth flotation method.
- (b) Conversion of concentrated ore to its oxide- roasting and calcination (definition, examples with equations).
- (c) Reduction of metallic oxides- some can be reduced by hydrogen, carbon and carbon monoxide (e.g. copper oxide, lead (II) oxide, iron (III) oxide and zinc oxide) and some cannot (e.g. AlβOβ, MgO). Active metals by electrolysis e.g. sodium, potassium and calcium. Equations with conditions should be given.
- (d) Electro refining β reference only.
(iii) Extraction of Aluminium.
- (a) Chemical method for purifying bauxite by using NaOH β Baeyer's Process only.
- (b) Electrolytic extraction β Hall Heroult's process only: Structure of electrolytic cell - the various components as part of the electrolyte, electrodes and electrode reactions. Description of the changes occurring, purpose of the substances used and the main reactions with their equations.
(iv) Alloy and Amalgam β composition and uses. Composition and uses of Stainless steel, magnalium, duralumin, brass, bronze, fuse metal / solder.