Question

The following reactions take place in the blast furnace in the preparation of impure iron. Identify the reaction pertaining to the formation of slag.

• A. $2\mathrm{C}\left(\mathrm{s}\right)+{\mathrm{O}}_2\to 2{\mathrm{CO}}_2\left(\mathrm{g}\right)$
• B. ${\mathrm{CaCO}}_3\left(\mathrm{s}\right)\to \mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)$
• C. $\mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{SiO}}_2\left(\mathrm{s}\right)\to {\mathrm{CaSiO}}_3\left(\mathrm{s}\right)$

Answer 1

The correct option is C

$\mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{SiO}}_2\left(\mathrm{s}\right)\to {\mathrm{CaSiO}}_3\left(\mathrm{s}\right)$

The explanation for the correct option:

(C) $\mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{SiO}}_2\left(\mathrm{s}\right)\to {\mathrm{CaSiO}}_3\left(\mathrm{s}\right)$

• Slag is a by-product that is separated from metal during smelting.
• During the preparation of impure iron, slag is obtained by the reaction of lime with silica.
• ${\mathrm{CaSiO}}_3$ is the main component of slag.

Hence option (C) is correct.

The explanation for incorrect options:

(A) $2\mathrm{C}\left(\mathrm{s}\right)+\mathrm{O}\to 2{\mathrm{CO}}_2\left(\mathrm{g}\right)$

• Carbon from coke reacts with hot air to give carbon dioxide, which further reacts with additional coke to give carbon monoxide.
• Highly exothermic reaction.

(B) ${\mathrm{CaCO}}_3\left(\mathrm{s}\right)\to \mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)$

• Decomposition of limestone $\left({\mathrm{CaCO}}_3\right)$ gives lime $\left(\mathrm{CaO}\right)$ and$\left({\mathrm{CO}}_2\right)$, around 1270K in the blast furnace.

Hence, the correct option is (C).