Question

Select the correct statement:

• A. Roasting involves heating the ore in the absence of air.
• B. Calcination involves heating the ore above its melting point.
• C. Smelting involves heating the ore with a suitable reducing agent and flux below its melting point.
• D. Calcination of calcium carbonate is endothermic.

Hint:

Calcination involves heating an ore in limited oxygen; calcium carbonate decomposes endothermically.

Answer 1

The Correct Option is D

To determine the correct statement from the given options, we need to understand the processes of roasting, calcination, and smelting in metallurgy.

1. Roasting: This process involves heating the ore in the presence of excess air or oxygen. It is primarily used for sulfide ores to convert them into oxides, releasing sulfur dioxide gas. The statement "Roasting involves heating the ore in the absence of air." is incorrect.
2. Calcination: This process involves heating the ore in the absence or limited supply of air, typically below or at its melting point, to bring about thermal decomposition. The statement "Calcination involves heating the ore above its melting point." is incorrect as it focuses on thermal decomposition without reaching melting points.
3. Smelting: This process involves heating the ore with a suitable reducing agent (like carbon) and a flux in order to extract the base metal. This process generally occurs below the melting point of the metal in question. However, as described, smelting often reaches temperatures above the melting points to combine and melt the materials together. Thus, the statement "Smelting involves heating the ore with a suitable reducing agent and flux below its melting point." is incorrect.
4. Calcination of Calcium Carbonate: This is an endothermic reaction where calcium carbonate (\(CaCO_3\)) is decomposed into calcium oxide (\(CaO\)) and carbon dioxide (\(CO_2\)) with the absorption of heat: \(CaCO_3 \rightarrow CaO + CO_2\\) The statement "Calcination of calcium carbonate is endothermic." is correct.

The correct answer is that the calcination of calcium carbonate is endothermic, making option 4 the right choice. This is due to the absorption of heat required to decompose \(CaCO_3\) into \(CaO\) and \(CO_2\).