In the extraction of iron in the blast furnace, limestone is used to?

In the extraction of iron in the blast furnace, limestone is used to remove impurities. Limestone, which is primarily composed of calcium carbonate (CaCO3), is added to the blast furnace as a flux. The flux reacts with the impurities in the iron ore, such as silica (SiO2), to form a slag, which can be easily removed. The limestone also decomposes to form calcium oxide (CaO), which reacts with the silica to form calcium silicate (CaSiO3), the main component of the slag. This process helps to purify the iron ore, removing impurities such as sulfur and phosphorus, which would otherwise weaken the iron. So, the correct option is "remove impurities."