Roasting results in the formation of oxides. Why are oxide ores are subjected to roasting?

To remove volatile impurities in the form of their oxides

The correct answer is option 4. To remove volatile impurities in the form of their oxides.

Here is why oxide ores are sometimes subjected to roasting: To remove volatile impurities in the form of their oxides

This is the most common reason for roasting oxide ores. Although they are already oxides of the desired metal, they might still contain impurities in the form of other metal oxides or combined with non-metallic elements. Roasting helps remove these volatile impurities by converting them into gaseous oxides that can be released.

Let us analyze the other options:

1.To avoid gangue particles: Gangue refers to unwanted minerals present in the ore that are not the metal of interest. Roasting doesn't directly remove gangue particles. It might help break down some gangue minerals that are combined with volatile elements, but the primary focus is on removing volatile impurities within the oxide ore itself.

2.To get crude metal by using an oxidizing agent: Roasting typically doesn't involve obtaining crude metal directly. While it uses oxygen (an oxidizing agent), the goal is not to produce the metal but to convert the volatile impurities into gaseous oxides for removal.

3.To make the ore porous: Making the ore porous can be a secondary benefit of roasting in some cases. As volatile components are driven off, they can leave behind a more porous structure. However, increasing porosity is not the primary purpose of roasting oxide ores.

Roasting oxide ores is primarily done to eliminate volatile impurities that can be converted into gaseous oxides during the heating process. This helps purify the desired metal oxide and prepare it for further extraction steps.