Question

\[A{{l}_{2}}{{O}_{3}}.3{{H}_{2}}O\xrightarrow{calcination}B+3{{H}_{2}}O\]
The name of product B is
(a)- corundum
(b)- bauxite
(c)- aluminum hydroxide
(d)- none of these

Answer 1

Hint: Alumina Hydrate or Alumina Hydroxide is a source of alumina. More correct name for it is Aluminum Hydroxide, \[A{{l}_{2}}{{O}_{3}}.3{{H}_{2}}O\]. It is generally present in the form of fine granular white powder.

Complete step by step solution:
Aluminum hydroxide or alumina trihydrate is a hydrated oxide of aluminum. In this crystal form, alumina hydrate exhibits a good chemical reactivity. Alumina hydrate can react with both base and acid, making it useful in many applications as raw material.

Aluminum hydroxide, or alumina trihydrate is a product formed in the Bayer process. Calcination is a step in Bayer’s process in which coarse crystals are separated through classification, and 90 percentage of the gibbsite manufactured is converted into alumina by washing, drying, and then heating aluminum hydroxide in a calciner or rotary kiln at temperature 1010-1260 ℃ to manufacture special grade alumina. During calcinations, the crystals of alumina hydrate lose the bound moisture and recrystallize to form alumina crystals. The particle size of alumina remains at 85-100 micron. The degree of calcination is a measure of the hardness of alumina. The reaction can be given as:
\[A{{l}_{2}}{{O}_{3}}.3{{H}_{2}}O\to A{{l}_{2}}{{O}_{3}}+3{{H}_{2}}O\]

So, the product B is \[A{{l}_{2}}{{O}_{3}}\].

Note: Pure alumina, is extracted from the mineral bauxite using hot concentrated sodium hydroxide solution in the Bayer Process. Further, the Hall-Héroult process is used to obtain Aluminum from the ore.