Which of the following slags is produced during extraction of iron?
Correct answer: (a)
Solution: 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. CaCO3→CaO+CO2 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+SiO2→CaSiO3 The calcium silicate melts and runs down through the furnace to form a layer on top of the molten iron.