Question

The reaction used to join railway tracks involves reducing agent:
A.Al
B.Mg
C.C
D.CO

Answer 1

Basically, a substance which loses electrons to other substances in a redox reaction and gets oxidized to the higher valency state is known as a reducing agent. Moreover, if the reducing agent does not pass the electrons to another substance in a reaction, then the reduction process cannot occur.

Complete step by step answer:
Generally, a reducing agent is one of the reactants of an oxidation reduction reaction which reduces the other reactant by giving out the electrons. The metals of s-block in the periodic table are said to be good reducing agents. So, when some substance is oxidized, it is said to lose electrons and the substance which receives electrons is said to be reduced and if the substance has a strong tendency to lose electrons then it is further said to be a strong reducing agent.
Now, the reaction used to join the railway track is as shown:
$F{e_2}{O_3} + Al \to A{l_2}{O_3} + 2Fe$
Now, there is an increase in the oxidation state of Al and since it undergoes oxidation, it is considered as a reducing agent. Basically, this reaction is known as a thermite reaction. In this reaction, the metal is formed by the reduction of a metal oxide by using aluminum powder as a reducing agent.
Hence, option A is correct.

Note: Aluminum is used as a reducing agent in the extraction of metals in those cases where the metal oxide is comparatively more reactive than zinc and which further cannot be reduced by carbon. For example, the oxides of manganese and chromium metals are not satisfactory reduced by carbon so these metals are extracted by the reduction of their oxides with aluminum powder.