Question

In the metallurgy of Iron, limestone is added to the ore. Why?

Answer 1

1. Iron is extracted from the ore Hematite.
2. Limestone is used as a flux since it will remove the impurities present in the ore.
3. Limestone$\mathbf{\left(}\mathit{C}\mathit{a}\mathit{C}{\mathit{O}}_{\mathbf{3}}\mathbf{\right)}$ forms Calcium Silicate with Silicon dioxide thereby forming slag.
4. Calcium Silicate is the slag.
5. Limestone first decomposes and forms Calcium Oxide. The reaction is,

$CaC{O}_3\left(s\right)\to \underset{Calciumoxide}{CaO\left(s\right)}+\underset{Carbondioxide}{C{O}_2\left(g\right)}$

$\underset{Flux}{CaO\left(s\right)}+\underset{Silicondioxide}{Si{O}_2\left(s\right)}\to \underset{Calciumsilicate\left(Slag\right)}{CaSi{O}_3\left(l\right)}$

So limestone is added to Iron for removing the impurities present in Ore, Hematite thereby acting as a Flux.