Reactivity Series PDF

Extraction of metals Only some unreactive metals such as silver, gold and platinum can occur freely in nature. Most metals react with other elements to form ores.  Major steps in extraction of metal  Ore concentration – Ore is purified and concentrated, unwanted...

Extraction of metals Only some unreactive metals such as silver, gold and platinum can occur freely in nature. Most metals react with other elements to form ores.  Major steps in extraction of metal  Ore concentration – Ore is purified and concentrated, unwanted rocks removed  Reduction to crude metal – Metal oxides to be reduced to metals, resulting in a mixture of metals collected  Refining to obtain pure metal – To obtain a specific metal, purify and remove unwanted metal impurities  the extraction of metals Method of extraction depends on the position of the metal in the reactivity series.  extraction of metal involves: o getting rid of the unwanted rock to obtain concentrated form of the mineral o obtaining pure metal from the mineral by chemical reactions  the extraction of metals Metals at the top of the reactivity series are very reactive:  bonds in their compounds are very strong  must be extracted by decomposing their compounds with electricity in an expensive process called electrolysis  aluminium is extracted from aluminium oxide by passing an electric current through it 2Al2O3 4Al + 3O2  Ways of Extraction  Potassium K Extracted by  Sodium Na electrolysis of  Calcium Ca molten chlorides  Magnesium Mg Extraction by  Aluminium Al electrolysis of  Zinc Zn molten Al2O3  Iron Fe Extraction by dissolved in  Tin Sn reduction of cryolite  Lead Pb oxides using  Copper Cu carbon  Mercury Hg  Silver Ag Roasting ore by  Gold Au heating alone  Platinum Pt Extraction of Iron Raw materials of extraction of Iron  Iron Ore – eg haematite ore [iron(III) oxide, Fe2O3]  Coke – carbon, C  Hot air – for the O2 in it  Limestone – calcium carbonate, CaCO3  Stage 1 – Production of carbon dioxide  Thecoke is ignited at the base and hot air blown in to burn the coke (carbon) to form carbon dioxide – C(s) + O2(g)  CO2(g)  Thelimestone is decomposed by heat to produce carbon dioxide & quicklime – CaCO3(s)  CaO(s) + CO2(g)  Stage 2 – Production of carbon monoxide  Athigh temperature, the carbon dioxide formed reacts with more coke (carbon) to form carbon monoxide – CO2(g) + C(s)  2CO(g)  Stage 3 – Reduction of haematite  The carbon monoxide removes the oxygen from the iron oxide ore.  This frees the iron, which is molten at the high blast furnace temperature, and flows down to the base of the blast furnace.  Fe2O3(s) + 3CO(g)  2Fe(l) + 3CO2(g)  Other possible ore reduction reactions are... – Fe2O3(s) + 3C(s)  2Fe(l) + 3CO(g) – 2Fe2O3 (s) + 3C(s)  4Fe(l) + 3CO2 (g)  Stage 3 – Reduction of haematite  Waste gases escape through the top of the furnace  Eg. Carbon monoxide, carbon dioxide, nitrogen… Stage 4 – Removal of Impurities  The original ore contains silica (SiO2, silicon dioxide). These react with limestone to form a molten slag of e.g. calcium silicate in 2 stages – CaCO3  CaO + CO2 – CaO + SiO2  CaSiO3  The molten slag forms a layer above the more dense molten iron and can be separately, and regularly, drained away. The iron is cooled and cast into pig iron ingots / transferred directly to a steel producing furnace  Slag can be used for road surfacing