Question

SiO2 in the extraction of iron in the blast furnace

Answer 1

The main impurity that occur with iron ore is silica (sand or rock) which is silicon dioxide.Silicon dioxide is solid at the furnace temperature
and the furnace would become blocked if it was not removed.Silicon dioxide reacts with calcium oxide to form calcium silicate (called slag) which is liquid in the furnace.Slag flows to the bottom of the furnace where it floats on the liquid iron and is easily removed.The chemical reaction as follows:
CaCO3 → CaO +CO2

CaO + SiO₂ → CaSiO₃