Question

Where do we use the roasting process?

Answer 1

Roasting:

• “In roasting, the ore is heated in a regular supply of air in a furnace at a temperature below the melting point of the metal.”
• Roasting involves the conversion of sulphide ore to its oxide in the presence of air by the evolution of SO₂. The product obtained is porous. The reaction is: $\mathrm{Metal}\mathrm{sulphide}+{\mathrm{O}}_2⟶\mathrm{Metal}\mathrm{oxide}+{\mathrm{SO}}_2$
• Some of the reactions involving sulfide ores are:

$$\begin{gathered} 2\mathrm{ZnS}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2\mathrm{ZnO}\left(\mathrm{s}\right)+2{\mathrm{SO}}_2\left(\mathrm{g}\right) \\ 2\mathrm{PbS}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2\mathrm{PbO}\left(\mathrm{s}\right)+2{\mathrm{SO}}_2\left(\mathrm{g}\right) \\ 2{\mathrm{Cu}}_2\mathrm{S}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{Cu}}_2\mathrm{O}\left(\mathrm{s}\right)+2{\mathrm{SO}}_2\left(\mathrm{g}\right) \end{gathered}$$

• The roasting process is done for the formation of oxide of metals from their sulfides.
• Sulfide ores are converted using the roasting process.