When limestone is heated strongly,it gives off $CO_2$. In metallurgy,this process is known as:

Roasting of sulphides gives the gas $X$ as a byproduct. This is a colourless gas with a choking smell of burnt sulphur and causes great damage to respiratory organs as a result of acid rain. Its aqueous solution is acidic,acts as a reducing agent,and its acid has never been isolated.
The gas $X$ is

Zinc is obtained from zinc blende by:

Roasting of copper pyrites ores is for the following purposes:

What is produced when zinc blende is roasted in air?

Which of the following reactions is an example of the calcination process?