Question

Give the reaction involved during the extraction of zinc from its ore by :

(1) roasting of zinc ore

(2) calcination of zinc ore

Answer 1

Part-1: Roasting of Zinc ore

• Roasting is a metallurgical process in which a gas-solid reaction occurs at an elevated temperature.
• In the Roasting process, the ores are heated with a regular supply of air in the furnace at a temperature below the melting point of the metal.
• This is done for Sulphide ores, in which Sulphide ore is heated to convert into oxides, and Sulphur dioxide gas is released.
• Zinc Sulphide is roasted in the presence of air to produce Zinc Oxide and Sulphur dioxide gas.
• $\underset{\mathrm{Zinc}\mathrm{Sulphide}}{2\mathrm{ZnS}(\mathrm{s}})+\underset{\mathrm{Oxygen}}{3{\mathrm{O}}_2\left(\mathrm{g}\right)}\to 2\underset{\mathrm{Zinc}\mathrm{Oxide}}{\mathrm{ZnO}\left(\mathrm{s}\right)}+\underset{\mathrm{Sulphur}\mathrm{dioxide}}{2{\mathrm{SO}}_2\left(\mathrm{g}\right)}$

Part-2: Calcination of Zinc ore

• In Calcination, the ore is heated in the absence or limited supply of air at a temperature below the melting point of the metal.
• Calcination is generally done for carbonated or hydroxide ore to convert them into their respective oxides.
• Zinc Carbonate is heated to convert into Zinc oxide and Carbon dioxide gas is released.
• $\underset{\mathrm{Zinc}\mathrm{Carbonate}}{{\mathrm{ZnCO}}_3\left(\mathrm{s}\right)}\to \underset{\mathrm{Zinc}\mathrm{Oxide}}{\mathrm{ZnO}\left(\mathrm{s}\right)}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}$