Question

In the metallurgy of iron, when limestone is added to the blast furnace, the calcium ions end up in:
A. Slag
B. Gangue
C. Metallic calcium
D. Calcium carbonate

Answer 1

Hint: In metallurgy or specially in the process smelting, molten of fusible metal is produced from infusible ore. This process generally takes place in the presence of heat, reducing agent and flux.

Complete Step by Step Answer:
Limestone is actually calcium carbonate. Calcium carbonate in a blast furnace decomposes to produce calcium dioxide along with carbon dioxide.

The reaction can be given as follows:
$CaC{{O}_{3}}\to CaO+C{{O}_{2}}$
In this reaction one mole of calcium carbonate is heated to form one mole of metal oxide ore that is calcium oxide along with carbon dioxide gas.

Blast furnace contains silicon dioxide. This calcium dioxide combines with the silicon dioxide to form calcium silicate.
The reaction can be given as follows:
$CaO+Si{{O}_{2}}\to CaSi{{O}_{3}}$
Slag is a compound of calcium oxide and silicon dioxide. Thus slag is produced in the metallurgy of iron, when limestone is added to the blast furnace.
Thus the correct option is A.

Note: Due to the action of limestone metal is smelted out of its ore and the ore appears to be in a glassy state. This glassy appearance of the ore is caused by the formation of slag during the smelting process on the surface of the ore.