Question

Aluminium is used in thermite welding because it:
A.) Is a light metal
B.) Has more affinity for oxygen
C.) Is a strong oxidising agent
D.) Is a reactive metal

Answer 1

Hint: To answer this we should first know about thermite. It is a pyrotechnic composition of metal powder and metal oxide. When ignited by heat, the thermite undergoes an exothermic reduction-oxidation (redox) reaction.

Complete step by step answer:
You should know that thermite is the trade name for one of the granular mixtures of aluminium metal and powdered ferric oxide.
The reduction of the metallic oxide with Al is known as the thermite process.
In thermite welding, aluminium powder is used along with ferric oxide. Aluminium has more affinity towards oxygen and it reduces ferric oxide to elemental iron during welding and also produces a lot of heat. The molten elemental iron thus formed will seal the broken parts to have strong bonding. Aluminium is also common because of its high boiling point and low cost. It is used in the welding process to join railway tracks.

Here in this reaction, we can see that aluminium powder is used as it is a strong reducing agent and it reduces $Fe_{ 2 }O_{ 3 }$ to iron. Reduced molten iron sinks and flows into the gap of the grinder thereby welding it.

$Fe_{ 2 }O_{ 3 }\quad +\quad 2Al\quad \rightarrow \quad Al_{ 2 }O_{ 3 }\quad +\quad 2Fe$

Hence, the correct answer to this question is option B.

Note: Most varieties of the composition of metal powder and metal oxide are not explosive but can create brief bursts of heat and high temperature in a small area. Its form of action is similar to that of other fuel-oxidizer mixtures, such as black powder.