Calcination is used in metallurgy for the removal of

Which process is used to convert hydrated alumina into anhydrous alumina?

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

Explain Calcination and Roasting in detail.

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

Which of the following factors is of $\text{no significance}$ for roasting sulphide ores to the oxides and not subjecting the sulphide ores to carbon reduction directly?