Iron is extracted from its ore in a blast furnace. The raw materials used are iron ore, coke, air, and limestone. State the role of coke and limestone. (4 marks)

Coke is used as a fuel in the blast furnace to provide the high temperatures needed for the chemical reactions to occur. It also helps to reduce the iron ore to iron metal by providing carbon for the reduction reaction.

Limestone is used as a flux in the blast furnace to help remove impurities from the iron ore. It reacts with the impurities in the ore to form a slag, which can be easily separated from the molten iron. This helps to improve the quality of the iron produced.

Role of Coke:

- Fuel: Coke is a high-carbon fuel that provides the intense heat required to melt the iron ore and facilitate chemical reactions.
- Reducing Agent: Coke reacts with oxygen in the air to produce carbon monoxide (CO), which reduces iron oxide (Fe2O3) in the iron ore to iron metal (Fe).

Role of Limestone:

- Flux: Limestone (calcium carbonate, CaCO3) reacts with impurities in the iron ore, such as silica (SiO2), to form calcium silicate (CaSiO3).
- Slag Formation: The calcium silicate is molten and has a lower density than molten iron. It floats on top of the iron, forming a protective layer known as slag.
- Removal of Sulfur: Limestone reacts with sulfur present in the iron ore to form calcium sulfide (CaS), which is absorbed into the slag and prevents it from contaminating the iron.