Question

Which is the strongest reduction agent?
A.Zn (s)
B.Cr (s)
C.\[{{{H}}_{{2}}}\] (g)
D.${{F}}{{{e}}^{{{2 + }}}}$ (aq)

Answer 1

Hint:Reducing agents are the substance that can donate electrons to reduce the other substance and they get oxidized since they now have lost some of their electrons. The ability of a substance to reduce depends on how easily they can lose their electron and thus in turn depends on the standard electric potential.

Complete step by step answer:
The more the reducing ability of a species the lower its reducing potential should be. So that it can easily get oxidized and reduce the other species.
A substance with lower (more negative) reduction potential tends to donate electrons and hence is said to be a reducing agent. On the other hand, a substance with higher (more positive) reduction potential tend to accept electrons and thus are oxidizing agents
Electrochemical series have metals arranged in order of their standard reduction potential.
Using electrochemical series if you try to arrange the given species in increasing order of reducing potential we will have
\[{{Z}}{{{n}}^{{{2 + }}}}{{/Zn < C}}{{{r}}^{{{3 + }}}}{{/Cr < F}}{{{e}}^{{{2 + }}}}{{/Fe < }}{{{H}}^{{ + }}}{{/}}{{{H}}_{{2}}}\]
So as we have already discussed species with the lowest reduction potential will be most reducing, therefore Zn will be the strongest reducing agent.

Thus, the correct answer is option A. Zn (s) is the strongest reducing agent.


Note:
Electrochemical series is also known as activity series. The series has an arrangement of elements in increasing order of their electrode potential (standard oxidation potential) or decreasing order of standard reduction potential. This has been established by measuring the electrode potential of various elements versus the standard hydrogen electrode. The element at the top of the series is the strong oxidizing agent and the element at the bottom of the series is the strongest reducing agent.