WAEC Chemistry 2013 Paper

Concept:Limestone acts as a flux to remove impurities in the blast furnace.Explanation:In the blast furnace, limestone ($\mathrm{CaCO_3}$) is heated and decomposes to form calcium oxide ($\mathrm{CaO}$) and carbon dioxide.The $\mathrm{CaO}$ then reacts with silica ($\mathrm{SiO_2}$), which is a common impurity in iron ore.This reaction produces slag, mainly calcium silicate ($\mathrm{CaSiO_3}$), which is molten and can be easily separated from the molten iron.Therefore, the main function of limestone is to remove the impurity (silica) from the ore.Answer:C. remove impurity