Question

The process of converting hydrated alumina into anhydrous alumina is called _______.

1. Roasting

2. Calcination

Answer 1

Calcination is a process in which the ore is heated strongly in the absence of air. It removes volatile impurities like CO${}_2$, SO${}_2$, moisture from the ore. It removes water from hydrated oxide the process of converting hydrated alumina into anhydrous alumina is called calcination.
$A{l}_2{O}_3.2H_{2}O\to A{l}_2{O}_3+2H_{2}O$

Note - Roasting is a process in which the sulphide ore is heated strongly in the presence of air. In roasting the ore is converted into its oxide. Smelting is a process in which the oxide ore in the fused state is reduced by carbon to the free metal. Dressing: There are many impurities like soil, stones, clay, etc., present in the ore. These impurities are called gangue. The removal of these impurities from ore is called dressing.