Redox Reactions of Iron

Iron is one of the world’s cheapest, most useful and most commonly produced metals there is today. As well as being hard and durable its uses are quite extensive. These uses range from being made into paper clips to cars. They also make up machines which help produce our homes clothing and food. Iron can refer to both the element as well as an alloy which is a mixture of iron and other metallic elements. Iron makes up one forth of the earths crust and is the main metal in the earth’s core. Iron metals are extracted from their ores (which is the original state of the iron).

To convert iron ore into metallic iron the oxygen must be removed from the ore.

This is caused by the reduction of the mineral oxide in the iron ore. The reducing agents that are used are coke (C) and carbon monoxide (CO). The reaction takes place in a Blast furnace or a direct reduction system.

http://www.chem.shef.ac.uk/chm131-2002/cha02dh/blast-furnace.html

As can be seen in this diagram crushed iron ore is placed into the top of the blast furnace with coke and limestone. Heated blasts of air at the temperature of 1000oC and put into the bottom of the furnace [this air is made up of 20% oxygen (O)].

The procedure for the blast furnace is as so:

1. In the blast furnace an exothermic reaction occurs and causes the coke (C) to oxidise to Carbon dioxide (CO).

C + O2 > CO2

2. There is then an endothermic reaction where the carbon dioxide reacts with the coke to form carbon monoxide.

CO2 + C > 2CO

3. There is then another exothermic reaction where the Iron (III) oxide in the ore is reduced to iron caused but the carbon monoxide.

Fe2O3 + 3CO > 2Fe + 3CO2

After this reaction occurs the iron travels to the bottom of the furnace and melts.

4.Alternatively, Iron (III) oxide is reduced to Iron (II) oxide by carbon monoxide:

Fe2O3 + CO > 2FeO + CO2

5. Where the temperature is high enough the coke will then react with iron (II) oxide, which will reduce it to a metallic iron.

FeO + C > Fe + CO

The rections that involve the iron are just simple reductions.

Fe3+ + 3e- > Fe

Fe3+ + e- > Fe2+

Fe2+ + 2e- > Fe