Which of the following processes involves heating a carbonate ore to form metal oxide?

Calcination

The correct answer is option is 4. Calcination.

The process that involves heating a carbonate ore to form a metal oxide is Calcination.

Calcination is a process used in metallurgy and other industries to heat a substance (such as a carbonate ore) in the absence or limited presence of air to bring about thermal decomposition or phase transition. In the context of carbonate ores, such as limestone (calcium carbonate) or malachite (copper carbonate), calcination involves heating the ore to a high temperature (usually between 700°C to 900°C) in a controlled environment, typically in a kiln or furnace. During calcination, the carbonate ore undergoes thermal decomposition, resulting in the release of carbon dioxide gas \((CO_2)\) and the formation of the corresponding metal oxide. For example, when calcium carbonate \((CaCO_3)\) is subjected to calcination, it decomposes into calcium oxide \((CaO)\) and carbon dioxide gas:

\(\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2\)

Similarly, other carbonate ores undergo similar decomposition reactions to yield metal oxides. The metal oxide obtained through calcination can then be further processed through various metallurgical methods to extract the desired metal.