Question

What is the role of lime or limestone in the extraction of Iron?

Answer 1

• The chemical formula of limestone is ${\mathrm{CaCO}}_3$.
• Limestone is a basic flux that can be used to form fusible slag from earthly impurities present in the ore.
• Limestone undergoes decomposition to form lime i.e. Calcium oxide $\left(\mathrm{CaO}\right)$ and Carbon dioxide.
• The decomposition reaction occurs as follows:
  $\underset{\left(\mathrm{Limestone}\right)}{{\mathrm{CaCO}}_3\left(\mathrm{s}\right)}\to \underset{\left(\mathrm{Lime}\right)}{\mathrm{CaO}\left(\mathrm{s}\right)}+{\mathrm{CO}}_2\left(\mathrm{g}\right)$
• The lime thus formed reacts with the Silicate present in the ore of Iron which is Silicon oxide.
• The chemical reaction occurs as follows:
  $\underset{\left(\mathrm{Lime}\right)}{\mathrm{CaO}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Silicates}\right)}{{\mathrm{SiO}}_2\left(\mathrm{s}\right)}\to \underset{\left(\mathrm{Slag}\right)}{\underset{\left(\mathrm{Calcium}\mathrm{silicate}\right)}{{\mathrm{CaSiO}}_3\left(\mathrm{l}\right)}}$
• Thus, limestone can be used to remove unwanted impurities from the ore of Iron during extraction.