Occurrence Of Metals

The processes involved in the extraction of metals require understanding the chemical reactions and treatments applied to the ores and impurities. Let's examine the statements provided:

1. Roasting of Malachite produces Cuprite.
This statement is incorrect. Roasting Malachite, which is basic copper carbonate, generally decomposes it to copper(II) oxide (CuO) and not Cuprite (Cu₂O).

2. Calcination of Calamine produces Zincite.
This statement is correct. Calamine, primarily zinc carbonate (ZnCO₃), undergoes calcination—a process of heating in absence of air—resulting in the formation of Zincite (ZnO) along with the release of carbon dioxide (CO₂).

3. Copper pyrites is heated with silica in a reverberatory furnace to remove iron.
This statement is correct. When copper pyrites (CuFeS₂) is heated with silica (SiO₂), iron is removed as iron silicate (FeSiO₃), aiding in copper extraction.

4. Impure silver is treated with aqueous KCN in the presence of oxygen followed by reduction with zinc metal.
This statement is correct. Impure silver is refined using the cyanide process, where it forms a soluble complex with cyanide ions in the presence of oxygen. Subsequent reduction by zinc metal results in pure silver.

In conclusion, statements 2, 3, and 4 are the correct processes related to metal extraction.