Concept:In the blast furnace, limestone, CaCO3, is added as a flux to form slag and remove impurities from iron ore.Explanation:The main impurity in iron ore is silicon dioxide, SiO2.Limestone is charged into the blast furnace together with coke and the iron ore.At the high temperature in the furnace, limestone decomposes to give calcium oxide and carbon dioxide:CaCO3ΔCaO+CO2The calcium oxide, CaO, reacts with the acidic impurity, SiO2, to form molten calcium silicate, which is the slag.This slag floats on top of the molten iron and is removed separately.Thus, the material used in forming the slag is calcium carbonate, CaCO3.Option C is the correct answer.
