Question

Alumino thermite process is used for the extraction of metals, whose oxides are:
(A) Strongly acidic
(B) Not easily reduced by carbon
(C) Not easily reduced by hydrogen
(D) Strongly basic

Answer 1

Hint: The thermite process was discovered by a German chemist named Hans Goldschmidt (1861-1923) in 1893. Goldschmidt was only interested in extracting very pure metals, but he soon came to know its value in welding, a process known as Thermite welding.

Complete step by step solution:

Alumino thermite is a process of extracting metals by reduction of a metal oxide to form metal using aluminium powder, the aluminium acts as a reducing agent. It is an exothermic reaction which liberates a large amount of heat. Practically, this method can be used to reduce all the metallic oxides, with oxide of magnesium being the only exception.

Here are few examples of Alumino thermite process:

* Reduction of ferrous oxide to ferrous metal
Iron (III) oxide is mixed with aluminium powder and is ignited with a burning magnesium ribbon. Aluminium reduces iron oxide to produce molten iron metal with the evolution of heat. The chemical reaction is gives as:

$$F{e}_2{O}_3+2Al\to 2Fe+A{l}_2{O}_3+Heat$$

* Cr₂O₃ is reduced to chromium metal.
A mixture of Chromic oxide and powdered aluminum in ratio of 3:1 and is ignited by a piece of magnesium ribbon. A large amount of heat is liberated during this process and chromic oxide is reduced to chromium. The chemical reaction is gives as:

$$C{r}_2{O}_3+2Al\to 2Cr+A{l}_2{O}_3+Heat$$

Note: This reduction property of aluminium is used in thermite welding for joining the broken pieces of heavy iron objects like girders, railway tracks or cracked machine parts of various machineries.