Question

Why is the formation of slag useful during the smelting of iron?

Short answer

Slag protects iron from oxidation.

Step-by-step solution

Oxidation of iron:

When iron is in contact with water and oxygen, it rusts. If salt is present, for example in seawater or salt spray, the iron tends to rust more quickly, as a result of chemical reactions. Iron metal is relatively unaffected by pure water or by dry oxygen.

Formation of slag:

The formation of slag is useful during the smelting of iron because the \(CaSi{O_3}\)slag is less dense than the molten iron, which means it can easily be separated. The less dense slag floats on iron and protects it from oxidation. Because if iron is exposed to oxygen it can easily oxidize to \(F{e_2}{O_3}\).