Question

: Aluminothermy used for the spot welding of large iron structures is based upon the fact that:
A. As compared to iron, aluminium has a greater affinity for oxygen.
B. As compared to aluminium, iron has a greater affinity for oxygen.
C. Reaction between aluminium and oxygen is endothermic.
D. Reaction between iron oxide and aluminium is exothermic.

Answer 1

Aluminothermy is a process where metal oxides get reduced to its metal in metallurgy. The metallurgy is a process that is used for the extraction of metals to obtain them in their pure form. The compounds of metals mixed with rocks, soil, sand, and impurities are referred to as minerals. These minerals are called ores. Metals can be extracted commercially from ores at low cost and minimum effort.

Complete step by step answer:
In aluminothermy is the process of metallurgy where reduction of metal oxides by oxidation of finely divided aluminum. In this process a great amount is developed, aluminum takes oxygen from the metal oxide and gets oxidized. This process is also known as the thermite process.
The Aluminothermy process is also used to spot welding of iron structures. In this process the aluminum takes oxygen from the metal oxide and gets oxidized is because the affinity of aluminum towards oxygen is greater than the iron metal.
This reaction is exothermic and developed a high amount of heat.
The reaction of this process is as follows,
$F{e_2}{O_{3}} + 2Al \to 2Fe + A{l_{2}}{O_3}$

So, the correct options are, A and D.

Additional information:
The metallurgical process can be understood by the following points:
-The first step is crushing and grinding of ores into a fine powder using a crusher. This is known as pulverization.
-Impurities can be removed from the ore and this process is called ore dressing or concentration of minerals.
- The concentration of ores is done by many methods, these are the hydrolytic method, magnetic separation, froth floatation, and roasting and calcination.

Note:
Roasting is a metallurgical process involving a gas-solid reaction in presence of air at high temperatures to purify the ore of the material.
In the case of roasting of sulfide ore done in metallurgy of copper. Due to partial roasting, the copper sulfide becomes copper oxide which further reacts with unreacted copper sulfide and gives auto reduction. The reaction is shown below.
$2C{u_2}S + 3{O_2} \to 2C{u_2}O + S{O_2}$ , $2C{u_2}O + C{u_2}S\; \to 6Cu + S{O_2}$ .