Question

Name the following:

(a) A compound that is added to lower the fusion temperature of the electrolytic bath in the extraction of aluminum.

(b) The process of heating an ore to a high temperature in the presence of air.

(c) The compound formed by the reaction between calcium oxide and silica.

Answer 1

(a) Cryolite $\left({\mathrm{Na}}_3{\mathrm{AlF}}_6\right)$ is a compound that is added to lower the fusion temperature of the electrolytic bath in the extraction of aluminum.

(b) Roasting is the process of heating an ore to a high temperature in the presence of air. It converts sulphide ores into oxides.

$4{\mathrm{FeS}}_2\left(\mathrm{s}\right)+11{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+8{\mathrm{SO}}_2\left(\mathrm{g}\right)$

(c) Calcium oxide $\left(\mathrm{CaO}\right)$ reacts with silica $\left({\mathrm{SiO}}_2\right)$ to form calcium silicate $\left({\mathrm{CaSiO}}_3\right)$ known as slag.

$\underset{\mathrm{calcium}\mathrm{oxide}}{\underbrace{\mathrm{CaO}\left(\mathrm{s}\right)}}+\underset{\mathrm{silica}}{\underbrace{{\mathrm{SiO}}_2\left(\mathrm{s}\right)}}\to \underset{\mathrm{slag}}{\underbrace{{\mathrm{CaSiO}}_3\left(\mathrm{l}\right)}}$