Intermediate Topic 689 of 1102 Inorganic Chemistry
Roasting and Calcination
Roasting heats sulfide ores in air; calcination heats carbonates without air.
In-depth explanation of Roasting and Calcination
Roasting and calcination are heat treatments that convert ores into oxides before reduction. Roasting heats sulfide ores strongly in excess air, converting them to an oxide and releasing sulfur dioxide, as in 2ZnS + 3O2 giving 2ZnO + 2SO2. The SO2 is usually captured and used to make sulfuric acid. Calcination heats carbonate or hydrated ores in limited air to drive off carbon dioxide or water, leaving the oxide. Both processes are carried out in furnaces before the oxide is reduced to metal.
Going deeper: Roasting and Calcination
Key ideas: Roasting heats sulfide ores in excess air below the melting point, forming oxide and SO2: 2ZnS + 3O2 gives 2ZnO + 2SO2. Calcination heats carbonate or hydrated ores in limited or no air: CaCO3 gives CaO + CO2, Al2O3.xH2O gives Al2O3 + xH2O. Both are conducted in a reverberatory or shaft furnace. Roasting removes S, As, Sb as volatile oxides; SO2 is captured for sulfuric acid.
Common mistakes and connections: Students interchange the terms: roasting is oxidation in air, calcination is thermal decomposition. Not all roasting uses oxygen to make the oxide; chloridizing roasting uses NaCl for Ag. Reaction heats are exothermic in roasting. Links to smelting, sulfuric acid by-product and environmental SO2 control.
Visualization of Roasting and Calcination
Roasting needs high temperature so that enough collisions exceed the activation energy; the sulfide converts to oxide and releases SO2. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Heating zinc carbonate gives zinc oxide and carbon dioxide: ZnCO3 giving ZnO + CO2.
Frequently asked questions about Roasting and Calcination
What is Roasting and Calcination?
Roasting heats sulfide ores in air; calcination heats carbonates without air.
Is Roasting and Calcination a beginner, intermediate or advanced topic?
Roasting and Calcination is a intermediate topic in Inorganic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Roasting and Calcination?
Study these earlier topics in Inorganic Chemistry first: Superheavy Elements, Metallurgy, Ore Concentration.
What comes after Roasting and Calcination?
The next topics in Inorganic Chemistry are Smelting and Ellingham Diagram.
Can I practise Roasting and Calcination with quizzes?
Yes. The interactive lesson includes a self-check question on Roasting and Calcination, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Roasting and Calcination fits in Inorganic Chemistry
Roasting and Calcination is topic 74 of 113 in Inorganic Chemistry.