chemistry C1 (3)

What is an ore?

• most metals are usually found combined with other elements, often oxygen, in rocks
• to be able to use the metal, it must be chemically separated form its compounds
• the rock is called an ore if it contains enough of the metal or metal compound to make it economically worthwhile to extract the metal
• ores are mined and may be concentrated before the metal is extracted and purified
• concentrating an ore involves the removal of waste rock from the mined ore
• which makes the extraction process more economical
• extracting a metal from its ore is expensive because the process requires a lot of energy so there must be a significant amount of the metal or metal compound to make this worthwhile
• iron ore is haematite
• aluminium ore is bauxite
• lead ore is galena
• copper ore is malachite

Which metals can be extracted using carbon?

• metals that can be extracted using carbon are: lead, zinc, iron, copper
• metals that cannot be extracted using carbon: aluminium, sodium
• iron and copper are both below carbon in the reactivity series, so carbon con be used to reduce the oxides and obtain the metal
• copper oxide + carbon to copper + carbon dioxide
• 2CuO + C to 2Cu + CO2
• iron oxide + carbon to iron + carbon dioxide
• 2Fe2O3 + 3C to 4Fe + 3CO2

• reduction: removal of oxygen from a compound
• ore: a rock containing enough metal to make it economical to extract
• reactivity series: a list of metals from the most reactive to the least reactive
• native: unreactive metals (such as silver, gold and platinum) found as elements in nature

The extraction of metals from their ores

• metal compounds are found in rocks called ores
• the commonest metal compounds found are metal carbonates, metal sulfides or metal oxides
• when metal carbonates are heated, they decompose to give the solid metal oxide and the gas, carbon dioxide, is given off
• when metal sulfides are heated in air they react with the oxygen in the air
• the products of this reaction are the solid metal oxide and the gas, sulfur dioxide
• if the metal is less reactive than carbon, then carbon will reduce the metal oxide to the metal
• when the metal oxide is heated with carbon, then carbon dioxide is formed along with the metal
• metal carbonate is heated and gives off carbon dioixde to from metal oxide
• metal sulfide is heated and gives off sulfur dioxide to form metal oxide
• the metal oxide is heated with carbon and gives off carbon dioxide the result is metal

Iron and steels

• iron is extracted from iron ore, containing iron(III)oxide, by reducing in a blast furnace
• in a blast furnace, the potassium manganate(VII), KMnO4, at the bottom of the tube produces oxygen gas when it is heated that is used in the reaction
• in the reaction you have just seen, the iron(III) oxide has been reduced to produce iron
• industrially, iron is extracted from iron ore called haematite which is mostly iron(III) oxide
• …