Which of the following slags is produced during the extraction of iron?

CaSiO₃

The correct answer is option 1. CaSiO₃.

Limestone is also decomposed to \(CaO\) which removes silicate impurity of the ore as slag. The slag is in a molten state and separates out from iron. Here, limestone acts as a flux.

Heat furnace decomposes the limestone to give calcium oxide.

\(CaCO_3 \longrightarrow CaO + CO_2\)

This is an endothermic reaction, absorbing heat from the furnace.It is therefore important not to add too much limestone because it would otherwise cool the furnace. Calcium oxide is a basic oxide and reacts with acidic oxides such as silicon dioxide present in the rock. Calcium oxide reacts with silicon dioxide to give calcium silicate.

\(CaO +SiO_2 \longrightarrow CaSiO_3\)

The calcium silicate melts and runs down through the furnace to form a layer on top of the molten iron.