- The most reactive metals are at the top of the series.
- They readily lose electrons to form cations and are hence oxidised easily.
- The opposite occurs for metals placed lower down as they are unreactive and do not easily lose their electrons.
- The tendency to become oxidised is thus linked to how reactive a metal is and therefore its position on the reactivity series.
- Metals higher up are therefore less resistant to oxidation than the metals placed lower down which are more resistant to oxidation.
- The position of the metal on the reactivity series determines the method of extraction.
- Higher placed metals (above carbon) have to be extracted using electrolysis as they are too reactive and cannot be reduced by carbon.
- Lower placed metals can be extracted by heating with carbon which reduces them.
Extraction of Iron
- The main ore of iron is haematite.
- Iron is extracted from the haematite in a blast furnace through reduction with carbon.
- The process is very important industrially due to the large scale use of iron in industry and society.
Carbon Extraction of Iron
Diagram of the extraction of iron in a blast furnace
Iron ore (Haematite), coke, limestone and air. Iron ore, coke and limestone are mixed together and fed into the top of the blast furnace. Hot air is blasted into the bottom of the blast furnace.
Coke is used as the starting material. It is an impure carbon and burns in the hot air blast to form carbon dioxide. This is a strongly exothermic reaction:
C(s) + O2(g) → CO2(g)
At the high temperatures in the furnace, carbon dioxide reacts with coke to form carbon monoxide:
CO2(g) + C (s) → 2CO (g)
Carbon monoxide (the reducing agent) reduces the Iron (III) oxide in the iron ore to form iron, which will melt and collect at the bottom of the furnace, where it is tapped off:
Fe2O3 (s) + 3CO (g) → 2Fe (IIl) + 3CO2 (g)
Limestone is added to the furnace to remove impurities in the ore. The calcium carbonate in the limestone decomposes to form calcium oxide:
CaCO3 (s) → CaO (s) + CO2 (g)
The calcium oxide reacts with the silicon dioxide, which is an impurity in the iron ore, to form calcium silicate. This melts and collects as a molten slag floating on top of the molten Iron which is tapped off separately:
CaO (s) → SiO2 (s) + CaSiO3 (l)