Question

A metal A, which is used in the thermite process, when heated with oxygen gives an oxide B, which is amphoteric in nature. Oxide B is:
(A) $2AlC{{l}_{3}}$
(B) $A{{l}_{2}}{{O}_{3}}$
(C) $NaAl{{O}_{2}}$
(D) $MgO$

Answer 1

Hint:
Thermite is a generic word used for a mixture of aluminium powder and metal oxide. Amphoteric work stands for compounds which can show both acidic and basic nature.

Complete step by step answer:
Aluminium is a very reactive metal, which in this sense means it oxidizes very quickly and produces a lot of heat while oxidizing.
Reduction of metal oxides with aluminium powder in which a large amount of heat is liberated is called the thermite process.
e.g. $F{{e}_{2}}{{O}_{3}}+2Al\to A{{l}_{2}}{{O}_{3}}+2Fe$
The above shown reaction occurs because aluminium can form more stable bonds with oxygen in comparison with iron. Thus, we can say that aluminium reduces the oxide of another metal because aluminium forms stronger and more stable bonds with oxygen than other metal.

The most common form of thermite is mixture of iron oxide and aluminium powder. When aluminium powder reacts with iron oxide or chromium oxide, a large amount of heat is released and about a temperature of 3500$^{\circ }C$ is attained which is enough to weld broken metallic parts.
Now, coming to the question, metal A is aluminium which is used in thermite process, when heated with oxygen gives oxide $A{{l}_{2}}{{O}_{3}}$ (oxide B) which is amphoteric in nature. We can give a reaction as below.

                                       \[A{{l}_{(s)}}\xrightarrow{{{O}_{2}}}A{{l}_{2}}{{O}_{3}}\]

Now, $A{{l}_{3}}{{O}_{3}}$ has a special characteristic that it can behave as an acid as well as a base. So, we call it amphoteric oxide.

Therefore, from above we can conclude that option (B) is the correct option to the given question.

Note:
As Aluminum is a metal, do not consider that it will also have basic oxides as other metals give, actually its oxides are amphoteric in nature. Also, you should remember that thermite reactions are highly exothermic and a lot of heat is evolved.